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Mars: 3-D Dunes
| Title |
Mars: 3-D Dunes |
| Explanation |
Get out your red/blue glasses [ http://mpfwww.jpl.nasa.gov/MPF/mpf/ glasses.html ] and treat yourself to this dramatic 3-D view of sand dunes on Mars [ http://mars.jpl.nasa.gov/ ]! The field of undulating dunes is found in Nili Patera, a volcanic depression in central Syrtis Major [ http://www.orbital9.com/mars/syrtis.shtml ], the most prominent dark feature on the Red Planet [ http://marsproject.com/syrtis.htm ]. Two different images from the orbiting Mars Global Surveyor spacecraft were combined to make this stereo picture [ http://mars.jpl.nasa.gov/mgs/msss/camera/images/moc_5_24_01/ stereo/index.html ], one taken in March 1999 and the other recorded in April 2001. Sculpted by winds [ http://antwrp.gsfc.nasa.gov/apod/ap000202.html ] like the sand dunes of Earth [ http://pubs.usgs.gov/gip/deserts/eolian/ ], these particular Martian dunes show no change in shape over the time [ http://www.giss.nasa.gov/data/mars/time/ ] separating the two images, a period equivalent to about one Martian year [ http://www.jps.net/gangale/mars/chronium/ chron1.htm ]. This cropped version of the 3-D [ http://www.lpi.usra.edu/research/stereo_atlas/SS3D.HTM ] picture spans an area around 2 kilometers across. Walking, you might cover that distance in about 20 minutes. |
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Spallanzani Crater
| title |
Spallanzani Crater |
| Description |
Although most of the best examples of layered sedimentary rock seen on Mars are found at equatorial and sub-tropical latitudes, a few locations seen at mid- and high-latitudes suggest that layered rocks are probably more common than we can actually see from orbit. One extremely good example of these "atypical" layered rock exposures is found in the 72 km-diameter (45 miles) crater, Spallanzani (58.4°S, 273.5°W). Located southeast of Hellas Planitia, the crater is named for the 18th Century Italian biologist, Lazzaro Spallanzani (1729-1799). Picture A presents a composite of the best Viking orbiter image (VO2-504B55) of the region with 4 pictures obtained June 1999 through January 2001 by the Mars Global Surveyor Mars Orbiter Camera (MOC). Each MOC narrow angle image is 3 km across. Taken in the MOC's "survey mode," all four images were acquired at roughly 12 meters (39 ft) per pixel. Picture B zooms-in on the portion of the composite image that includes the 4 MOC images (the 100%-size view is 20 m (66 ft) per pixel). Other craters in the region near Spallanzani show features--at Viking Orbiter scale--that are reminiscent of the layering seen in Spallanzani. Exactly what these layers are made of and how they came to be where we see them today are mysteries, but it is possible that they are similar to the materials seen in the many craters and chasms of the equatorial latitudes on Mars. Images Credit: NASA/JPL/Malin Space Science Systems |
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Mid-Winter Dust Storms Near
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| title |
Mid-Winter Dust Storms Near Hellas Planitia |
| Description |
One of the primary objectives for the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during the Extended Mission is to continue daily monitoring of martian weather as expressed in clouds, dust storms, and patches of polar frost. During the Primary Mission, which lasted from March 1999 through January 2001, changes that occurred over a single martian year (687 Earth days) were observed. Now it is possible to see what the martian atmosphere will do for at least two-thirds of a second martian year, because the Extended Mission will run into April 2002. This picture captures two dust storms, each large enough to cover Arizona or New Mexico. One is located near the lower left, the other at the lower right. Taken on April 8, 2001 (mid-southern winter), this is a mosaic of six MOC daily global images centered around Hellas Planitia in the martian southern hemisphere. Hellas Planitia is the dominant elliptical feature just below the center of the picture. The bright, nearly white surfaces along the lower (southern) edge of the picture are covered by wintertime frost. The strong temperature difference between the winter frost and the warmer air just off the edge of this polar cap generates winds that---at this time of year---are often strong enough to lift dust into large, reddish-brown, billowy clouds. North is up and sunlight illuminates the area from the upper left. The martian equator forms the arc along the top of the picture, 500 kilometers (km) is equal to about 311 miles. The approximately 500 kilometer-wide circular feature just above the center is the crater Huygens. Image Credit: NASA/JPL/Malin Space Science Systems |
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Highest-Resolution View of "
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| title |
Highest-Resolution View of "Face on Mars |
| Description |
A key aspect of the Mars Global Surveyor (MGS) Extended Mission is the opportunity to turn the spacecraft and point the Mars Orbiter Camera (MOC) at specific features of interest. A chance to point the spacecraft comes about ten times a week. Throughout the Primary Mission (March 1999 - January 2001), nearly all MGS operations were conducted with the spacecraft pointing "nadir"---that is, straight down. In this orientation, opportunities to hit a specific small feature of interest were in some cases rare, and in other cases non-existent. In April 1998, nearly a year before MGS reached its Primary Mission mapping orbit, several tests of the spacecraft's ability to be pointed at specific features was conducted with great success (e.g., Mars Pathfinder landing site, Viking 1 site, and Cydonia landforms). When the Mars Polar Lander was lost in December 1999, this capability was again employed to search for the missing lander. Following the lander search activities, a plan to conduct similar off-nadir observations during the MGS Extended Mission was put into place. The Extended Mission began February 1, 2001. On April 8, 2001, the first opportunity since April 1998 arose to turn the spacecraft and point the MOC at the popular "Face on Mars" feature. Viking orbiter images acquired in 1976 showed that one of thousands of buttes, mesas, ridges, and knobs in the transition zone between the cratered uplands of western Arabia Terra and the low, northern plains of Mars looked somewhat like a human face. The feature was subsequently popularized as a potential "alien artifact" in books, tabloids, radio talk shows, television, and even a major motion picture. Given the popularity of this landform, a new high-resolution view was targeted by pointing the spacecraft off-nadir on April 8, 2001. On that date at 20:54 UTC (8:54 p.m., Greenwich time zone), the MGS was rolled 24.8° to the left so that it was looking at the "face" 165 km to the side from a distance of about 450 km. The resulting image has a resolution of about 2 meters (6.6 feet) per pixel. If present on Mars, objects the size of typical passenger jet airplanes would be distinguishable in an image of this scale. An earlier picture obtained in June 2000 was combined with the new, April 2001 image, to produce a stereo ("3-D") view of the western portion of the hill ("3-D" glasses with red for left eye and blue for right eye are needed to view the anaglyph). The large "face" picture, above, covers an area about 3.6 kilometers (2.2 miles) on a side, the 3-D picture [ http://www.msss.com/mars_images/moc/extended_may2001/face/index.html ] is about 1 km (0.62 mi) wide. Sunlight illuminates the images from the left/lower left. Images Credit: NASA/JPL/Malin Space Science Systems |
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Changes Over a Martian Year
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| title |
Changes Over a Martian Year -- New Dark Slope Streaks in Lycus Sucli |
| Description |
Now in its Extended Mission, Mars Global Surveyor (MGS) is into its second Mars year of systematic observations of the red planet. With the Extended Mission slated to run through April 2002, the Mars Orbiter Camera (MOC) is being used, among other things, to look for changes that have occurred in the past martian year. Because Mars is farther from the Sun than Earth, its year is longer---about 687 Earth days. The two pictures shown here cover the same portion of Lycus Sulci, a rugged, ridged terrain north of the giant Olympus Mons volcano. The interval between the pictures span 92% of a martian year (August 2, 1999 to April 27, 2001). Dark streaks considered to result from the avalanching of dry, fine, bright dust are seen in both images. The disruption of the surface by the avalanching materials is thought to cause them to appear darker than their surroundings, just as the 1997 bouncing of Mars Pathfinder's airbags and the tire tracks made by the Sojourner rover left darkened markings indicating where the martian soil had been disrupted and disturbed. The arrows in the April 2001 picture indicate eight new streaks that formed on these slopes in Lycus Sulci since August 1999. These observations suggest that a new streak forms approximately once per martian year per kilometer (about 0.62 miles) along a slope. In both images, north is toward the top/upper right and sunlight illuminates each from the left. Dark (as well bright) slope streaks are most common in the dust-covered martian regions of Tharsis, Arabia, and Elysium. Additional examples of dark slope streaks can be seen in the following earlier MOC image media releases: * "Recent Movements: New Landslides in Less than 1 Martian Year," March 12, 2000 [ http://www.msss.com/mars_images/moc/lpsc2000/3_00_massmovement/ ] * "Dark Slope Streaks on Elysium Basin Buttes," July 19, 1999 [ http://www.msss.com/mars_images/moc/7_19_99_fifthMars/18_slopes/ ] Images Credit: NASA/JPL/Malin Space Science Systems |
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Four Mars Years of South Pol
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| title |
Four Mars Years of South Polar Changes |
| Description |
One of the most profound discoveries that would not have been possible if NASA's Mars Global Surveyor mission had not been extended beyond its primary mission of one Mars year (687 Earth days) is that of dramatic changes that take place in the south polar residual ice cap each martian year. To make this discovery, the Mars Orbiter Camera on the spacecraft had to be employed during a second Mars year to repeat images of sites on the south polar cap that had been imaged during the primary mission. The initial discovery was made in 2001, when the camera team repeated images of portions of the south polar cap that had already been imaged in 1999. The goal of these images was to obtain stereo views, which would allow investigators to see the topography of the cap in three dimensions and to measure the thickness of the polar ice layers. It was not possible to produce the desired 3-D views. To the team's surprise, the landforms of the south polar cap had changed. The south polar residual cap -- that is, the portion of the ice cap that remains bright and retains ice throughout the southern summer season -- was seen in 1997 and 1999 images to have a complex terrain of broad, relatively flat mesas, small buttes, and many pits and troughs. Pits are generally circular and in some areas visually resemble a stack of thin slices of Swiss cheese. Very early in the Mars Global Surveyor mission, the Mars Orbiter Camera team speculated that these landforms must be carved into frozen carbon dioxide, because they look so unfamiliar and because Viking orbiter infrared measurements indicated that the south polar cap is cold enough consist of frozen carbon dioxide, even in summer. The observations made by Mars Orbiter Camera in 2001, during the first part of the extended mission, showed that the scarps and pit walls of the south polar cap had retreated at an average rate of about 3 meters (10 feet) since 1999. In other words, they were retreating 3 meters per Mars year (and, of course, most of that retreat takes place during the summer). In some places on the cap, the scarps retreat less than 3 meters a Mars year, and in others it can retreat as much as 8 meters (26 feet) per martian year. Of the two volatile materials one is likely to find in a frozen state on Mars -- water and carbon dioxide -- it is carbon dioxide that is volatile enough to permit scarp retreat rates like those observed by the Mars Orbiter Camera. Over time, south polar pits merge to become plains, mesas turn into buttes, and buttes vanish forever. Since 2001, two additional Mars years have elapsed. A scientific benefit of having a long extended mission for Mars Global Surveyor has been the opportunity to document how the polar cap is changing each year. Four images are shown here, plus an animation at left presenting the four frames in sequence. The location is near 86.3 degrees south latitude, 49.4 degrees west longitude, and the images show the same portion of the south polar residual, cap as it appeared in 1999, 2001, 2003, and 2005. Comparing the images or viewing the animation makes it evident that the landscape of the south polar cap has been changing rapidly over the past four martian years. Each year that Mars Global Surveyor has been in orbit, the landforms of the south polar residual cap have gotten smaller, and the carbon dioxide removed from the cap has not been re-deposited. The implication is that Mars presently has a warm (and possibly warming) climate, with new carbon dioxide going into the atmosphere every year. The other implication is that, at some time in the not-too-distant past, the planet had a colder climate, so that the layers of carbon dioxide could be deposited in the first place. If one takes the rate of scarp retreat and projects it backwards to fill in all of the pits and troughs with the carbon dioxide that has been removed from them, one finds that the colder climate might only have occurred a few centuries to a few tens of thousands of years ago. This kind of time scale is not unlike that of the climate changes that have been recorded on Earth, including the Ice Ages and the smaller fluctuations that have occurred since the last Ice Age (e.g., the "Little Ice Age" of the mid-14th through mid-19th centuries). After the discovery that the pits were enlarging and that we were not seeing carbon-dioxide deposition, it was suggested that interannual variations might be large enough to permit such deposition on a short timescale. However, two Mars years of additional observations show no large magnitude annual differences. Variations that would permit carbon dioxide deposition may require decades. And to see such variations may require many more Mars years of observations by orbiting spacecraft. The Mars Orbiter Camera was built and is operated by Malin Space Science Systems, San Diego, Calif. Mars Global Surveyor left Earth on Nov. 7, 1996, and began orbiting Mars on Sept. 12, 1997. JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Science Mission Directorate, Washington. Credit: NASA/JPL/MSSS |
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Spying Changes in Mars' Sout
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| title |
Spying Changes in Mars' South Polar Cap |
| Description |
This animated image shows Mars in motion over the last six years. Images from the Mars Orbiter Camera aboard the Mars Global Surveyor spacecraft have documented dramatic changes in the planet's south polar cap. The south polar residual cap of Mars is composed of layered, frozen carbon dioxide. In 1999, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) showed that the carbon dioxide layers have been eroded to form a variety of circular pits, arcuate scarps (arc-shaped slopes), troughs, buttes, and mesas. In 2001, MOC images designed to provide repeated views of the areas imaged in 1999--with the hope of creating stereo (3-D) images, so that the height of scarps and depth of pits could be measured--showed that the scarps had retreated, pits enlarged, and buttes and mesas shrank. Only carbon dioxide is volatile enough in the martian environment to have caused such dramatic changes. The scarps were seen to retreat at an average rate of 3 meters (nearly 10 feet) per Mars year. Most of the scarp retreat occurs during the southern summer season, in some areas the scarps move as much as 8 meters (26 feet), in others, only 1 meter (3.3 feet) per Mars year. Credit: NASA/JPL/MSSS |
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Northern Terra Meridiani Roc
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| title |
Northern Terra Meridiani Rocks and Cliffs in 3-D |
| Description |
Extended Mission operations for the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) include opportunities that come up about 10 times a week to turn and point the MGS spacecraft so that MOC can photograph a feature of high scientific interest. Many of these images are targeted to the site of a previous MOC image, so that a stereoscopic ("3-D") view can be obtained. The top picture shows a 115 kilometers (~72 miles) wide portion of northern Terra Meridiani, a region of vast layered rock outcrops similar to portions of southeastern Utah and northern Arizona on Earth. The white box in this context image, located near 2.2°N, 1.3°W, shows the location of the high resolution stereo view obtained by MOC by combining a picture taken March 10, 1999 (FHA-00541) with one obtained by pointing the spacecraft on May 28, 2001 (EO4-02223). The stereo view, which requires red (left-eye) and blue (right-eye) "3-D" glasses to be seen, covers an area approximately 2.3 km (1.4 mi) wide by 6.2 km (3.9 mi) long. The full-resolution view is seen at nearly 1.5 meters (5 ft) per pixel, a scale at which objects the size of airplanes and school buses might be seen. The landscape revealed by the 3-D view is a rugged terrain with steep cliffs and no fresh impact craters. This terrain seems most un-Mars-like compared to the typical cratered and dusty views MOC has provided since it began taking data in September 1997. In fact, one of the MOC science team members remarked, "If I'd seen this landscape used in a movie about Mars five years ago, I'd have said the director had no clue what Mars is supposed to look like." An irregular depression with a flat, mottled, light-toned floor dominates the scene. Small dark ridges on the depression floor near the top center of the image are dunes or drifts formed by wind transport of sandy sediment. The sharp buttes, mesas, and steep cliffs are all indicators that this terrain consists of a broad exposure of martian bedrock. North is up and sunlight illuminates each picture from the left/upper left. Images Credit: NASA/JPL/Malin Space Science Systems |
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Erosion of North Polar Layer
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| title |
Erosion of North Polar Layers and Genesis of nearby Sand Dunes |
| Description |
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) is used by the MOC science team as a tool to test hypotheses about the geology, geomorphology, and meteorology of Mars. In 1999, MOC images revealed that the layers of the martian north polar cap are divided into two distinct units: an upper, light-toned sequence of layers, and a lower, darker-toned suite of layers. The team suspected that the lower unit, because of its dark tone and apparent association with nearby dune fields, might be a source of windblown sand. However, most of the 1999 images were of very low contrast because the frequent dust storms in the region made the atmosphere extremely hazy. Very few images of the north polar cap were obtained in 2000 because it was first hidden during the long winter's night, then coated by springtime frost. By early 2001, the north polar cap was in summer and the MOC team set out to test the idea that sand is eroding out of the lower unit. This picture, obtained in February 2001, shows streamers of dark sand coming from outcrops of the lower, dark-toned unit. The streamers join a nearby dune field less than a few kilometers (less than a mile) away. Erosion of the lower layered unit liberates sand that was long ago deposited in these layers. The upper unit, by contrast, contains almost no sand. Wind erosion of the lower unit leads to creation of steep scarps as the sand is removed and the upper unit is undermined. The sand moves downwind (in this case, toward the bottom left of the image) and creates dunes. The new views of the martian north polar cap obtained in 1999 and 2001 suggest that it may not contain as much water ice as previously believed. Indeed, the amount of ice may be as little as half of what was once thought. The picture shown here is 3 km (1.9 mi) wide and illuminated from the lower left. Another picture showing the upper and lower layered sequences of the north polar cap can be seen by clicking here: "MOC Extended Mission View of North Polar Layers," 11 February 2002. Photo Credit: NASA/JPL/Malin Space Science Systems |
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North Polar Cap in Summer
| title |
North Polar Cap in Summer |
| Description |
In the middle of January 2001, Mars Global Surveyor (MGS) completed one Mars year in its ~380 km-high (236 mi) mapping orbit. The mapping orbit was originally achieved in late February 1999. In March of that year, MGS conducted a series of operations in preparation for full-up mapping, first calibrating its scientific instruments and then operating in a mode in which the high gain antenna was held fixed against the body of the spacecraft. During this Fixed High Gain Antenna period, 'contingency science' observations were made in case the high gain antenna failed to properly deploy. The wide angle view of the martian north polar cap shown on the left was acquired on March 13, 1999, during early northern summer. The image on the right was acquired almost exactly one Mars year later, on January 26, 2001. The light-toned surfaces are residual water ice that remains through the summer season. The nearly circular band of dark material surrounding the cap consists mainly of sand dunes formed and shaped by wind. The north polar cap is roughly 1100 kilometers (680 miles) across. Close inspection will show that there are differences in the frost cover between the two images (for example, in the upper center of each image, and on the left edge center). Although these changes appear small, they are in fact quite large--the change in frost covering is equivalent to the amount of frost that would be evaporated (in the case of areas that are darker) or deposited (in areas where frost is still on the ground) in almost 5 months. What gives rise to such large changes in the heat budget for the polar caps from one year to the next is not known. Changes in the coloration and brightness of the polar cap suggest dust, deposited perhaps by dust storms during critical periods of the year, may play an important role. Photo Credit: NASA/JPL/Malin Space Science Systems |
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Martian South Polar Pits in
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| title |
Martian South Polar Pits in Layer of Frozen Carbon Dioxide |
| Description |
One of the most profound benefits of being able to continue photographing Mars in the Mars Global Surveyor (MGS) Extended Mission is the opportunity to go back and re-image a site that was seen in the previous martian year. New MGS Mars Orbiter Camera (MOC) images have provided a startling observation: The residual martian south polar cap is changing. The fact that it is changing suggests that Mars may have major, global climate changes that are occurring on the same time scales as Earth's most recent climate shifts, including the last Ice Age. MOC images of the south polar cap taken in 1999 were compared with images of the same locations taken in 2001, and it was discovered that pits had enlarged, mesas had shrunk, and small buttes had vanished. In all, the scarps that enclose the pits and bound the mesas and buttes retreated about 3 meters (3.3 yards) in 1 martian year (687 Earth days). This rapid retreat of polar scarps can only occur if the ice is frozen carbon dioxide (also known as "dry ice"). Retreat of scarps made of water ice is much slower and would not have been measurable from one martian year to the next. The portion of the martian south polar cap that persists through summer is called the residual polar cap. The two sets of four pictures shown here are from four places on the residual south polar cap. The pictures from 1999 were taken in October of that year, the corresponding pictures from 2001 were acquired in August, approximately 1 Mars year after the 1999 images were obtained. In each case, the pictures are illuminated by sunlight from the upper left, and each shows an area about 250 meters (273 yards) across. The polar cap is layered, and the layers have eroded to form pits, troughs, mesas, and buttes. The pits form as sunlight warms frozen carbon dioxide during southern spring and summer, and the ice sublimes away. There is so much carbon dioxide that it does not all go away in one summer---in fact, it may take hundreds to thousands of years to disappear. These new observations indicate that the south polar residual cap is not permanent. It is disappearing, a little bit more each southern spring and summer season. At the present rate, a layer 3 m thick can be completely eroded away in a few tens of martian years. Since each layer is equivalent to about 1% of the mass of the present atmosphere (which is 95% carbon dioxide), if sufficient carbon dioxide is buried in the south polar cap, the mass of the atmosphere could double in a few hundred to a thousand Mars years. That could lead to profound changes in the environment. For example, it would change how much and where wind erosion would occur, and where and for how long liquid water could survive at or near the surface. It also means that Mars may have been very different in the recent past (perhaps only a few thousands of years ago). On today's Mars, the ice is eroding, but in the past that material had to have been deposited. The martian climate was probably colder, and, there was more carbon dioxide in the atmosphere. For some reason, large amounts of carbon dioxide froze at the south pole---one might say that there was a "Martian Ice Age"---and this freezing occurred on a time scale similar to that of the most recent Ice Age on Earth. Mars is changing, and it is changing on a time scale that we can measure and observe. If all of the carbon dioxide that is being released into the atmosphere from the south polar cap is not freezing out somewhere else, and if it is not being adsorbed into the martian soil, then it must be causing the atmospheric pressure to increase. If this is so, and if one were to assume that the entire known volume of the polar cap is made of carbon dioxide that sublimes at the same rate we see today, then it could increase the martian atmospheric pressure by as much as 10 times, to about 1/10th the density of Earth's atmosphere, in just the next few thousand years. Although this atmosphere would not be breathable, carbon dioxide is a "greenhouse gas" that would cause the global temperature to increase considerably and make it easier for liquid water to persist elsewhere on the planet. Perhaps, just perhaps, a thickening martian atmosphere would eventually make it easier for people to live on Mars. This new MGS MOC discovery is described in a paper published December 7, 2001, in the journal, Science. Read a more detailed discussion [ http://www.msss.com/mars_images/moc/CO2_Science_rel/malin_etal.html ] of these results (but less detailed than the Science article). Images Credit: NASA/JPL/Malin Space Science Systems |
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Sand Dunes of Nili Patera in
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| title |
Sand Dunes of Nili Patera in 3-D |
| Description |
The most exciting new aspect of the Mars Global Surveyor (MGS) Extended Mission is the opportunity to turn the spacecraft and point the Mars Orbiter Camera (MOC) at specific features of interest. Opportunities to point the spacecraft come about ten times a week. Throughout the Primary Mission (March 1999 - January 2001), nearly all MGS operations were conducted with the spacecraft pointing "nadir"---that is, straight down. A search for the missing Mars Polar Lander in late 1999 and early 2000 demonstrated that pointing the spacecraft could allow opportunities for MOC to see things that simply had not entered its field of view during typical nadir-looking operations, and to target areas previously seen in a nadir view so that stereo ("3-D") pictures could be derived. One of the very first places photographed by the MOC at the start of the Mapping Mission in March 1999 was a field of dunes located in Nili Patera, a volcanic depression in central Syrtis Major. A portion of this dune field was shown in a media release on March 11, 1999, "Sand Dunes of Nili Patera, Syrtis Major". Subsequently, the image was archived with the NASA Planetary Data System, as shown in the Malin Space Science Systems MOC Gallery. On April 24, 2001, an opportunity arose in which the MGS could be pointed off-nadir to take a new picture of the same dune field. By combining the nadir view from March 1999 and the off-nadir view from April 2001, a stereoscopic image was created. The anaglyph shown here must be viewed with red (left-eye) and blue (right-eye) "3-D" glasses. The dunes and the local topography of the volcanic crater's floor stand out in sharp relief. The images, taken more than one Mars year apart, show no change in the shape or location of the dunes---that is, they do not seem to have moved at all since March 1999. Image Credit: NASA/JPL/Malin Space Science Systems |
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"Not Vegetation!" Defrosting
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| title |
"Not Vegetation!" Defrosting Sand Dunes in Late Southern Winter |
| Description |
As winter gives way to spring in the martian southern hemisphere, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) is observing the retreat of the south polar frost cap as sunlight falls upon it for the first time in several months. One of the most aesthetically-pleasing aspects of the spring defrosting process is the pattern that is created on the martian sand dune fields. Dunes are usually among the first surfaces to begin showing signs of change in late winter when temperatures are just beginning to creep above -125° C (-193° F, 148 K). The pattern of spots on the dunes in the above MOC picture was observed on June 8, 2001. The location of the dune field near 62°S, 155°W, is shown in the color context view, which was acquired at the same time. Dark spots and streaks on defrosting sand dunes were first observed by MOC in the northern hemisphere in 1998. Similar dark-spotted dunes in the southern hemisphere were described at a NASA/Mars Global Surveyor Space Science Update media briefing in 1999. Despite the "sensation" one gets when looking at pictures of spotted, defrosting martian dunes (i.e., the sensation that these images show some form of life, like vegetation, growing on Mars) these features are a normal, common manifestation of the springtime defrosting process on Mars. The ices involved--because of the low temperatures at these locations--are probably both frozen water and carbon dioxide, though it is unclear as to whether one type of ice dominates over the other in controlling the appearance and coalescence of the dark spots. It is known from the first martian year of MOC operations that by summer all of the frost--and thus all of the spots--on the dunes will be gone. North is up and sunlight illuminates the scene from the upper left in both pictures. The color context view covers an area approximately 115 km (72 miles) across, the high resolution image covers 3 km by 22 km (1.9 by 13.6 mi). Images Credit: NASA/JPL/Malin Space Science Systems |
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May 1999 Dust Storm in Valle
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PIA02045
Sol (our sun)
Mars Orbiter Camera
| Title |
May 1999 Dust Storm in Valles Marineris |
| Original Caption Released with Image |
Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC) captured this view of a dust storm within the Ius and Melas Chasms of the Valles Marineris trough system on May 16, 1999. The dust storm is seen in the lower 1/3 of the image. It occurs at the junction between eastern Ius Chasma and western Melas Chasma. The apparent motion of the storm is approximately from the south (bottom of image) toward the north. The dust cloud forms a sharp front along its northern margin, which is seen along the north wall of Ius and Melas Chasms--in fact, at the time the image was taken, the dust had advanced up over the north wall of Melas Chasma (upper portion of lower right third of image) and was advancing across the upland that separates this chasm from western Candor Chasma. For a clear-atmosphere view of western Candor and Melas Chasms, see "Western Melas and Candor Chasms, Valles Marineris, MOC2-105, 25 March 1999" [ http://www.msss.com/mars/global_surveyor/camera/images/3_25_99_vmcolor/index.html ]. For scale, note that the large crater south of Hebes Chasma, Perrotin, is about 95 kilometers (59 miles) across. Bluish-white clouds in the image are interpreted to consist of water ice. The pink/red clouds of the dust storm occur closer to the ground, at a lower altitude than the water ice clouds. One of the most interesting aspects of this dust storm is that Valles Marineris was observed to have a dust storm at exactly the same time of year, one Martian year ago. During its approach to Mars, MOC obtained a picture of the planet on July 2,1997, just prior to the Mars Pathfinder landing. At the time, it was winter in the southern hemisphere, and dust clouds were observed within Valles Marineris. The picture is seen in "Mars Orbiter Camera Views Mars Pathfinder Landing Site,MOC2-1, 3 July 1997" [ http://www.msss.com/mars/global_surveyor/camera/images/c9/index.html ]. It will be interesting to see if similar storms occur within the Valles Marineris 1 and 2 Mars years hence. The next times will be in early April 2001 and mid-February 2003. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO. |
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Erosion of North Polar Layer
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PIA03777
Sol (our sun)
Mars Orbiter Camera
| Title |
Erosion of North Polar Layers and Genesis of nearby Sand Dunes |
| Original Caption Released with Image |
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) is used by the MOC science team as a tool to test hypotheses about the geology, geomorphology, and meteorology of Mars. In 1999, MOC images revealed that the layers of the martian north polar cap are divided into two distinct units: an upper, light-toned sequence of layers, and a lower, darker-toned suite of layers. The team suspected that the lower unit, because of its dark tone and apparent association with nearby dune fields, might be a source of windblown sand. However, most of the 1999 images were of very low contrast because the frequent dust storms in the region made the atmosphere extremely hazy. Very few images of the north polar cap were obtained in 2000 because it was first hidden during the long winter's night, then coated by springtime frost. By early 2001, the north polar cap was in summer and the MOC team set out to test the idea that sand is eroding out of the lower unit. This picture, obtained in February 2001, shows streamers of dark sand coming from outcrops of the lower, dark-toned unit. The streamers join a nearby dune field less than a few kilometers (less than a mile) away. Erosion of the lower layered unit liberates sand that was long ago deposited in these layers. The upper unit, by contrast, contains almost no sand. Wind erosion of the lower unit leads to creation of steep scarps as the sand is removed and the upper unit is undermined. The sand moves downwind (in this case, toward the bottom left of the image) and creates dunes. The new views of the martian north polar cap obtained in 1999 and 2001 suggest that it may not contain as much water ice as previously believed. Indeed, the amount of ice may be as little as half of what was once thought. The picture shown here is 3 km (1.9 mi) wide and illuminated from the lower left. |
|
Four Mars Years of South Pol
…
PIA04295
Sol (our sun)
Mars Orbiter Camera
| Title |
Four Mars Years of South Polar Changes |
| Original Caption Released with Image |
One of the most profound discoveries that would not have been possible if NASA's Mars Global Surveyor mission had not been extended beyond its primary mission of one Mars year (687 Earth days) is that of dramatic changes that take place in the south polar residual ice cap each martian year. To make this discovery, the Mars Orbiter Camera on the spacecraft had to be employed during a second Mars year to repeat images of sites on the south polar cap that had been imaged during the primary mission. The initial discovery was made in 2001, when the camera team repeated images of portions of the south polar cap that had already been imaged in 1999. The goal of these images was to obtain stereo views, which would allow investigators to see the topography of the cap in three dimensions and to measure the thickness of the polar ice layers. It was not possible to produce the desired 3-D views. To the team's surprise, the landforms of the south polar cap had changed. The south polar residual cap -- that is, the portion of the ice cap that remains bright and retains ice throughout the southern summer season -- was seen in 1997 and 1999 images to have a complex terrain of broad, relatively flat mesas, small buttes, and many pits and troughs. Pits are generally circular and in some areas visually resemble a stack of thin slices of Swiss cheese. Very early in the Mars Global Surveyor mission, the Mars Orbiter Camera team speculated that these landforms must be carved into frozen carbon dioxide, because they look so unfamiliar and because Viking orbiter infrared measurements indicated that the south polar cap is cold enough consist of frozen carbon dioxide, even in summer. The observations made by Mars Orbiter Camera in 2001, during the first part of the extended mission, showed that the scarps and pit walls of the south polar cap had retreated at an average rate of about 3 meters (10 feet) since 1999. In other words, they were retreating 3 meters per Mars year (and, of course, most of that retreat takes place during the summer). In some places on the cap, the scarps retreat less than 3 meters a Mars year, and in others it can retreat as much as 8 meters (26 feet) per martian year. Of the two volatile materials one is likely to find in a frozen state on Mars -- water and carbon dioxide -- it is carbon dioxide that is volatile enough to permit scarp retreat rates like those observed by the Mars Orbiter Camera. Over time, south polar pits merge to become plains, mesas turn into buttes, and buttes vanish forever. Since 2001, two additional Mars years have elapsed. A scientific benefit of having a long extended mission for Mars Global Surveyor has been the opportunity to document how the polar cap is changing each year. Four images are shown here, plus an animation at left presenting the four frames in sequence. The location is near 86.3 degrees south latitude, 49.4 degrees west longitude, and the images show the same portion of the south polar, residual cap as it appeared in 1999, 2001, 2003, and 2005. Comparing the images or viewing the animation makes it evident that the landscape of the south polar cap has been changing rapidly over the past four martian years. Each year that Mars Global Surveyor has been in orbit, the landforms of the south polar residual cap have gotten smaller, and the carbon dioxide removed from the cap has not been re-deposited. The implication is that Mars presently has a warm (and possibly warming) climate, with new carbon dioxide going into the atmosphere every year. The other implication is that, at some time in the not-too-distant past, the planet had a colder climate, so that the layers of carbon dioxide could be deposited in the first place. If one takes the rate of scarp retreat and projects it backwards to fill in all of the pits and troughs with the carbon dioxide that has been removed from them, one finds that the colder climate might only have occurred a few centuries to a few tens of thousands of years ago. This kind of time scale is not unlike that of the climate changes that have been recorded on Earth, including the Ice Ages and the smaller fluctuations that have occurred since the last Ice Age (e.g., the "Little Ice Age" of the mid-14th through mid-19th centuries). After the discovery that the pits were enlarging and that we were not seeing carbon-dioxide deposition, it was suggested that interannual variations might be large enough to permit such deposition on a short timescale. However, two Mars years of additional observations show no large magnitude annual differences. Variations that would permit carbon dioxide deposition may require decades. And to see such variations may require many more Mars years of observations by orbiting spacecraft. The Mars Orbiter Camera was built and is operated by Malin Space Science Systems, San Diego, Calif. Mars Global Surveyor left Earth on Nov. 7, 1996, and began orbiting Mars on Sept. 12, 1997. JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Science Mission Directorate, Washington. |
|
Four Mars Years of South Pol
…
PIA04295
Sol (our sun)
Mars Orbiter Camera
| Title |
Four Mars Years of South Polar Changes |
| Original Caption Released with Image |
One of the most profound discoveries that would not have been possible if NASA's Mars Global Surveyor mission had not been extended beyond its primary mission of one Mars year (687 Earth days) is that of dramatic changes that take place in the south polar residual ice cap each martian year. To make this discovery, the Mars Orbiter Camera on the spacecraft had to be employed during a second Mars year to repeat images of sites on the south polar cap that had been imaged during the primary mission. The initial discovery was made in 2001, when the camera team repeated images of portions of the south polar cap that had already been imaged in 1999. The goal of these images was to obtain stereo views, which would allow investigators to see the topography of the cap in three dimensions and to measure the thickness of the polar ice layers. It was not possible to produce the desired 3-D views. To the team's surprise, the landforms of the south polar cap had changed. The south polar residual cap -- that is, the portion of the ice cap that remains bright and retains ice throughout the southern summer season -- was seen in 1997 and 1999 images to have a complex terrain of broad, relatively flat mesas, small buttes, and many pits and troughs. Pits are generally circular and in some areas visually resemble a stack of thin slices of Swiss cheese. Very early in the Mars Global Surveyor mission, the Mars Orbiter Camera team speculated that these landforms must be carved into frozen carbon dioxide, because they look so unfamiliar and because Viking orbiter infrared measurements indicated that the south polar cap is cold enough consist of frozen carbon dioxide, even in summer. The observations made by Mars Orbiter Camera in 2001, during the first part of the extended mission, showed that the scarps and pit walls of the south polar cap had retreated at an average rate of about 3 meters (10 feet) since 1999. In other words, they were retreating 3 meters per Mars year (and, of course, most of that retreat takes place during the summer). In some places on the cap, the scarps retreat less than 3 meters a Mars year, and in others it can retreat as much as 8 meters (26 feet) per martian year. Of the two volatile materials one is likely to find in a frozen state on Mars -- water and carbon dioxide -- it is carbon dioxide that is volatile enough to permit scarp retreat rates like those observed by the Mars Orbiter Camera. Over time, south polar pits merge to become plains, mesas turn into buttes, and buttes vanish forever. Since 2001, two additional Mars years have elapsed. A scientific benefit of having a long extended mission for Mars Global Surveyor has been the opportunity to document how the polar cap is changing each year. Four images are shown here, plus an animation at left presenting the four frames in sequence. The location is near 86.3 degrees south latitude, 49.4 degrees west longitude, and the images show the same portion of the south polar, residual cap as it appeared in 1999, 2001, 2003, and 2005. Comparing the images or viewing the animation makes it evident that the landscape of the south polar cap has been changing rapidly over the past four martian years. Each year that Mars Global Surveyor has been in orbit, the landforms of the south polar residual cap have gotten smaller, and the carbon dioxide removed from the cap has not been re-deposited. The implication is that Mars presently has a warm (and possibly warming) climate, with new carbon dioxide going into the atmosphere every year. The other implication is that, at some time in the not-too-distant past, the planet had a colder climate, so that the layers of carbon dioxide could be deposited in the first place. If one takes the rate of scarp retreat and projects it backwards to fill in all of the pits and troughs with the carbon dioxide that has been removed from them, one finds that the colder climate might only have occurred a few centuries to a few tens of thousands of years ago. This kind of time scale is not unlike that of the climate changes that have been recorded on Earth, including the Ice Ages and the smaller fluctuations that have occurred since the last Ice Age (e.g., the "Little Ice Age" of the mid-14th through mid-19th centuries). After the discovery that the pits were enlarging and that we were not seeing carbon-dioxide deposition, it was suggested that interannual variations might be large enough to permit such deposition on a short timescale. However, two Mars years of additional observations show no large magnitude annual differences. Variations that would permit carbon dioxide deposition may require decades. And to see such variations may require many more Mars years of observations by orbiting spacecraft. The Mars Orbiter Camera was built and is operated by Malin Space Science Systems, San Diego, Calif. Mars Global Surveyor left Earth on Nov. 7, 1996, and began orbiting Mars on Sept. 12, 1997. JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Science Mission Directorate, Washington. |
|
Four Mars Years of South Pol
…
PIA04295
Sol (our sun)
Mars Orbiter Camera
| Title |
Four Mars Years of South Polar Changes |
| Original Caption Released with Image |
One of the most profound discoveries that would not have been possible if NASA's Mars Global Surveyor mission had not been extended beyond its primary mission of one Mars year (687 Earth days) is that of dramatic changes that take place in the south polar residual ice cap each martian year. To make this discovery, the Mars Orbiter Camera on the spacecraft had to be employed during a second Mars year to repeat images of sites on the south polar cap that had been imaged during the primary mission. The initial discovery was made in 2001, when the camera team repeated images of portions of the south polar cap that had already been imaged in 1999. The goal of these images was to obtain stereo views, which would allow investigators to see the topography of the cap in three dimensions and to measure the thickness of the polar ice layers. It was not possible to produce the desired 3-D views. To the team's surprise, the landforms of the south polar cap had changed. The south polar residual cap -- that is, the portion of the ice cap that remains bright and retains ice throughout the southern summer season -- was seen in 1997 and 1999 images to have a complex terrain of broad, relatively flat mesas, small buttes, and many pits and troughs. Pits are generally circular and in some areas visually resemble a stack of thin slices of Swiss cheese. Very early in the Mars Global Surveyor mission, the Mars Orbiter Camera team speculated that these landforms must be carved into frozen carbon dioxide, because they look so unfamiliar and because Viking orbiter infrared measurements indicated that the south polar cap is cold enough consist of frozen carbon dioxide, even in summer. The observations made by Mars Orbiter Camera in 2001, during the first part of the extended mission, showed that the scarps and pit walls of the south polar cap had retreated at an average rate of about 3 meters (10 feet) since 1999. In other words, they were retreating 3 meters per Mars year (and, of course, most of that retreat takes place during the summer). In some places on the cap, the scarps retreat less than 3 meters a Mars year, and in others it can retreat as much as 8 meters (26 feet) per martian year. Of the two volatile materials one is likely to find in a frozen state on Mars -- water and carbon dioxide -- it is carbon dioxide that is volatile enough to permit scarp retreat rates like those observed by the Mars Orbiter Camera. Over time, south polar pits merge to become plains, mesas turn into buttes, and buttes vanish forever. Since 2001, two additional Mars years have elapsed. A scientific benefit of having a long extended mission for Mars Global Surveyor has been the opportunity to document how the polar cap is changing each year. Four images are shown here, plus an animation at left presenting the four frames in sequence. The location is near 86.3 degrees south latitude, 49.4 degrees west longitude, and the images show the same portion of the south polar, residual cap as it appeared in 1999, 2001, 2003, and 2005. Comparing the images or viewing the animation makes it evident that the landscape of the south polar cap has been changing rapidly over the past four martian years. Each year that Mars Global Surveyor has been in orbit, the landforms of the south polar residual cap have gotten smaller, and the carbon dioxide removed from the cap has not been re-deposited. The implication is that Mars presently has a warm (and possibly warming) climate, with new carbon dioxide going into the atmosphere every year. The other implication is that, at some time in the not-too-distant past, the planet had a colder climate, so that the layers of carbon dioxide could be deposited in the first place. If one takes the rate of scarp retreat and projects it backwards to fill in all of the pits and troughs with the carbon dioxide that has been removed from them, one finds that the colder climate might only have occurred a few centuries to a few tens of thousands of years ago. This kind of time scale is not unlike that of the climate changes that have been recorded on Earth, including the Ice Ages and the smaller fluctuations that have occurred since the last Ice Age (e.g., the "Little Ice Age" of the mid-14th through mid-19th centuries). After the discovery that the pits were enlarging and that we were not seeing carbon-dioxide deposition, it was suggested that interannual variations might be large enough to permit such deposition on a short timescale. However, two Mars years of additional observations show no large magnitude annual differences. Variations that would permit carbon dioxide deposition may require decades. And to see such variations may require many more Mars years of observations by orbiting spacecraft. The Mars Orbiter Camera was built and is operated by Malin Space Science Systems, San Diego, Calif. Mars Global Surveyor left Earth on Nov. 7, 1996, and began orbiting Mars on Sept. 12, 1997. JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Science Mission Directorate, Washington. |
|
Four Mars Years of South Pol
…
PIA04295
Sol (our sun)
Mars Orbiter Camera
| Title |
Four Mars Years of South Polar Changes |
| Original Caption Released with Image |
One of the most profound discoveries that would not have been possible if NASA's Mars Global Surveyor mission had not been extended beyond its primary mission of one Mars year (687 Earth days) is that of dramatic changes that take place in the south polar residual ice cap each martian year. To make this discovery, the Mars Orbiter Camera on the spacecraft had to be employed during a second Mars year to repeat images of sites on the south polar cap that had been imaged during the primary mission. The initial discovery was made in 2001, when the camera team repeated images of portions of the south polar cap that had already been imaged in 1999. The goal of these images was to obtain stereo views, which would allow investigators to see the topography of the cap in three dimensions and to measure the thickness of the polar ice layers. It was not possible to produce the desired 3-D views. To the team's surprise, the landforms of the south polar cap had changed. The south polar residual cap -- that is, the portion of the ice cap that remains bright and retains ice throughout the southern summer season -- was seen in 1997 and 1999 images to have a complex terrain of broad, relatively flat mesas, small buttes, and many pits and troughs. Pits are generally circular and in some areas visually resemble a stack of thin slices of Swiss cheese. Very early in the Mars Global Surveyor mission, the Mars Orbiter Camera team speculated that these landforms must be carved into frozen carbon dioxide, because they look so unfamiliar and because Viking orbiter infrared measurements indicated that the south polar cap is cold enough consist of frozen carbon dioxide, even in summer. The observations made by Mars Orbiter Camera in 2001, during the first part of the extended mission, showed that the scarps and pit walls of the south polar cap had retreated at an average rate of about 3 meters (10 feet) since 1999. In other words, they were retreating 3 meters per Mars year (and, of course, most of that retreat takes place during the summer). In some places on the cap, the scarps retreat less than 3 meters a Mars year, and in others it can retreat as much as 8 meters (26 feet) per martian year. Of the two volatile materials one is likely to find in a frozen state on Mars -- water and carbon dioxide -- it is carbon dioxide that is volatile enough to permit scarp retreat rates like those observed by the Mars Orbiter Camera. Over time, south polar pits merge to become plains, mesas turn into buttes, and buttes vanish forever. Since 2001, two additional Mars years have elapsed. A scientific benefit of having a long extended mission for Mars Global Surveyor has been the opportunity to document how the polar cap is changing each year. Four images are shown here, plus an animation at left presenting the four frames in sequence. The location is near 86.3 degrees south latitude, 49.4 degrees west longitude, and the images show the same portion of the south polar, residual cap as it appeared in 1999, 2001, 2003, and 2005. Comparing the images or viewing the animation makes it evident that the landscape of the south polar cap has been changing rapidly over the past four martian years. Each year that Mars Global Surveyor has been in orbit, the landforms of the south polar residual cap have gotten smaller, and the carbon dioxide removed from the cap has not been re-deposited. The implication is that Mars presently has a warm (and possibly warming) climate, with new carbon dioxide going into the atmosphere every year. The other implication is that, at some time in the not-too-distant past, the planet had a colder climate, so that the layers of carbon dioxide could be deposited in the first place. If one takes the rate of scarp retreat and projects it backwards to fill in all of the pits and troughs with the carbon dioxide that has been removed from them, one finds that the colder climate might only have occurred a few centuries to a few tens of thousands of years ago. This kind of time scale is not unlike that of the climate changes that have been recorded on Earth, including the Ice Ages and the smaller fluctuations that have occurred since the last Ice Age (e.g., the "Little Ice Age" of the mid-14th through mid-19th centuries). After the discovery that the pits were enlarging and that we were not seeing carbon-dioxide deposition, it was suggested that interannual variations might be large enough to permit such deposition on a short timescale. However, two Mars years of additional observations show no large magnitude annual differences. Variations that would permit carbon dioxide deposition may require decades. And to see such variations may require many more Mars years of observations by orbiting spacecraft. The Mars Orbiter Camera was built and is operated by Malin Space Science Systems, San Diego, Calif. Mars Global Surveyor left Earth on Nov. 7, 1996, and began orbiting Mars on Sept. 12, 1997. JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Science Mission Directorate, Washington. |
|
Four Mars Years of South Pol
…
PIA04295
Sol (our sun)
Mars Orbiter Camera
| Title |
Four Mars Years of South Polar Changes |
| Original Caption Released with Image |
One of the most profound discoveries that would not have been possible if NASA's Mars Global Surveyor mission had not been extended beyond its primary mission of one Mars year (687 Earth days) is that of dramatic changes that take place in the south polar residual ice cap each martian year. To make this discovery, the Mars Orbiter Camera on the spacecraft had to be employed during a second Mars year to repeat images of sites on the south polar cap that had been imaged during the primary mission. The initial discovery was made in 2001, when the camera team repeated images of portions of the south polar cap that had already been imaged in 1999. The goal of these images was to obtain stereo views, which would allow investigators to see the topography of the cap in three dimensions and to measure the thickness of the polar ice layers. It was not possible to produce the desired 3-D views. To the team's surprise, the landforms of the south polar cap had changed. The south polar residual cap -- that is, the portion of the ice cap that remains bright and retains ice throughout the southern summer season -- was seen in 1997 and 1999 images to have a complex terrain of broad, relatively flat mesas, small buttes, and many pits and troughs. Pits are generally circular and in some areas visually resemble a stack of thin slices of Swiss cheese. Very early in the Mars Global Surveyor mission, the Mars Orbiter Camera team speculated that these landforms must be carved into frozen carbon dioxide, because they look so unfamiliar and because Viking orbiter infrared measurements indicated that the south polar cap is cold enough consist of frozen carbon dioxide, even in summer. The observations made by Mars Orbiter Camera in 2001, during the first part of the extended mission, showed that the scarps and pit walls of the south polar cap had retreated at an average rate of about 3 meters (10 feet) since 1999. In other words, they were retreating 3 meters per Mars year (and, of course, most of that retreat takes place during the summer). In some places on the cap, the scarps retreat less than 3 meters a Mars year, and in others it can retreat as much as 8 meters (26 feet) per martian year. Of the two volatile materials one is likely to find in a frozen state on Mars -- water and carbon dioxide -- it is carbon dioxide that is volatile enough to permit scarp retreat rates like those observed by the Mars Orbiter Camera. Over time, south polar pits merge to become plains, mesas turn into buttes, and buttes vanish forever. Since 2001, two additional Mars years have elapsed. A scientific benefit of having a long extended mission for Mars Global Surveyor has been the opportunity to document how the polar cap is changing each year. Four images are shown here, plus an animation at left presenting the four frames in sequence. The location is near 86.3 degrees south latitude, 49.4 degrees west longitude, and the images show the same portion of the south polar, residual cap as it appeared in 1999, 2001, 2003, and 2005. Comparing the images or viewing the animation makes it evident that the landscape of the south polar cap has been changing rapidly over the past four martian years. Each year that Mars Global Surveyor has been in orbit, the landforms of the south polar residual cap have gotten smaller, and the carbon dioxide removed from the cap has not been re-deposited. The implication is that Mars presently has a warm (and possibly warming) climate, with new carbon dioxide going into the atmosphere every year. The other implication is that, at some time in the not-too-distant past, the planet had a colder climate, so that the layers of carbon dioxide could be deposited in the first place. If one takes the rate of scarp retreat and projects it backwards to fill in all of the pits and troughs with the carbon dioxide that has been removed from them, one finds that the colder climate might only have occurred a few centuries to a few tens of thousands of years ago. This kind of time scale is not unlike that of the climate changes that have been recorded on Earth, including the Ice Ages and the smaller fluctuations that have occurred since the last Ice Age (e.g., the "Little Ice Age" of the mid-14th through mid-19th centuries). After the discovery that the pits were enlarging and that we were not seeing carbon-dioxide deposition, it was suggested that interannual variations might be large enough to permit such deposition on a short timescale. However, two Mars years of additional observations show no large magnitude annual differences. Variations that would permit carbon dioxide deposition may require decades. And to see such variations may require many more Mars years of observations by orbiting spacecraft. The Mars Orbiter Camera was built and is operated by Malin Space Science Systems, San Diego, Calif. Mars Global Surveyor left Earth on Nov. 7, 1996, and began orbiting Mars on Sept. 12, 1997. JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Science Mission Directorate, Washington. |
|
Three Years of Monitoring Ma
…
PIA04297
Sol (our sun)
Thermal Emission Spectromete
…
| Title |
Three Years of Monitoring Mars' Atmospheric Dust (Animation) |
| Original Caption Released with Image |
[ http://photojournal.jpl.nasa.gov/archive/PIA04297.mpeg ] Animation This movie shows the daily abundance of dust in the martian atmosphere over a period of three full martian years, from April 1999 through February 2005. The Thermal Emission Spectrometer instrument on NASA's Mars Global Surveyor orbiter has been tracking the weather on Mars for six years. The infrared spectrum observed by this instrument yields information about the spectral properties of the dust and the temperature of the atmosphere. These two properties can then be used to derive how much dust is in the atmosphere. Of particular interest are large regional and global dust storms that occur during summer in the southern hemisphere each Mars year. The 2001 storm was by far the largest, lasting over six months (June to October, 2001) and covering the entire planet. The storms in the other two Mars years shown here were much smaller and never covered the planet. The most recent storm season (June 2003 through January 2005) actually had two separate storms, one in June and a second in December. Unlike most large martian dust storms that start in the southern hemisphere, the December storm began in the north and swept toward the equator. Between storms the atmosphere becomes quite clear, with much smaller dust storms scattered throughout the year and over the planet. Seasons on Mars are determined by the position of Mars in its orbit around the Sun. The position is measured in degrees of solar longitude (Ls) around the orbit, beginning at 0 degrees Ls at the northern spring equinox, progressing to 90 degrees Ls at the start of northern summer, 180 degrees Ls at the fall equinox, 270 degrees Ls at the start of northern winter, and finally back to 360 degrees, or 0 degrees, Ls at the spring equinox. Dust abundance is measured as opacity (tau), with values of 0 tau representing a completely clear atmosphere, and values of 2 indicating that it is nearly impossible to see through to the surface. The Thermal Emission Spectrometer is operated by a team led at Arizona State University, Tempe. Mars Global Surveyor left Earth on Nov. 7, 1996, and began orbiting Mars on Sept. 12, 1997. JPL, a division of the California Institute of Technology, Pasadena, manages Mars Global Surveyor for NASA's Science Mission Directorate, Washington. |
|
MOC's 200,000th Image
PIA07995
Sol (our sun)
Mars Orbiter Camera
| Title |
MOC's 200,000th Image |
| Original Caption Released with Image |
3 June 2005 On 17 May 2005, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) acquired its 200,000th image since the spacecraft began orbiting Mars on 12 September 1997. This image shows details on the floor and in the ejecta blanket of a northern middle-latitude martian crater, was received on Earth the following day. Its red wide angle context frame was also acquired at the same time (see PIA07996 [ http://photojournal.jpl.nasa.gov/catalog/PIA07996 ]). This image marks a milestone for the Mars Global Surveyor mission, which has returned nearly four times the number of images of both the Viking 1 and Viking 2 orbiters, combined, in the late 1970s. An additional point of comparison, the two Viking camera systems returned about 70 Gbytes of data, MOC thus far has returned 365 Gbytes (after decompression). The MOC is really a system consisting of three cameras: (1) a narrow angle camera, essentially a telescope, that obtains extremely high resolution views ranging from about 0.5 to about 14 meters per pixel, (2) a red wide angle camera that is used to take context images, daily global maps, and other selected images, and (3) a blue wide angle camera that also acquires daily global maps, views of the martian limb, and other selected targets. Both wide angle cameras can obtain images with resolutions in the range of 0.24 to 7.5 kilometers per pixel. The first images acquired by MOC were taken during the third orbit of MGS on 15 September 1997. MGS conducted a pre-mission series of observations between mid-September 1997 and February 1999. Then, MGS conducted its 1 Mars year Primary Mission from March 1999 through January 2001. The Extended Mission phase for MGS began in February 2001 and continues to this day. "Location near": 32.7°N, 185.1°W "Image width": ~3 km (~1.9 mi) "Illumination from": lower left "Season": Northern Autumn |
|
MOC's 200,001st Image
PIA07996
Sol (our sun)
Mars Orbiter Camera
| Title |
MOC's 200,001st Image |
| Original Caption Released with Image |
3 June 2005 On 17 May 2005, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) acquired its 200,000th image since the spacecraft began orbiting Mars on 12 September 1997. This red wide angle context frame was acquired at the same time as the narrow angle image (see PIA07995 [ http://photojournal.jpl.nasa.gov/catalog/PIA07995 ] showing details on the floor and in the ejecta blanket of a northern middle-latitude martian crater, which was received on Earth the previous day). This image marks a milestone for the Mars Global Surveyor mission, which has returned nearly four times the number of images of both the Viking 1 and Viking 2 orbiters, combined, in the late 1970s. An additional point of comparison, the two Viking camera systems returned about 70 Gbytes of data, MOC thus far has returned 365 Gbytes (after decompression). The MOC is really a system consisting of three cameras: (1) a narrow angle camera, essentially a telescope, that obtains extremely high resolution views ranging from about 0.5 to about 14 meters per pixel, (2) a red wide angle camera that is used to take context images, daily global maps, and other selected images, and (3) a blue wide angle camera that also acquires daily global maps, views of the martian limb, and other selected targets. Both wide angle cameras can obtain images with resolutions in the range of 0.24 to 7.5 kilometers per pixel. The first images acquired by MOC were taken during the third orbit of MGS on 15 September 1997. MGS conducted a pre-mission series of observations between mid-September 1997 and February 1999. Then, MGS conducted its 1 Mars year Primary Mission from March 1999 through January 2001. The Extended Mission phase for MGS began in February 2001 and continues to this day. "Location near": 32.7°N, 185.1°W "Image width": ~115 km (~71 mi) "Illumination from": lower left "Season": Northern Autumn |
|
Evidence for Recent Wind Act
…
PIA01495
Sol (our sun)
Mars Orbiter Camera
| Title |
Evidence for Recent Wind Action on Martian Sand Dunes |
| Original Caption Released with Image |
Recognizing that Mars is a desert planet, science fiction writers, scientists, and proponents of Mars exploration have, for decades, written and talked about "The Sands of Mars." The first martian sand dunes were observed by the Mariner 9 spacecraft in 1972. Ever since then, however, it has been unclear as to whether these dunes are active in today's extremely thin martian atmosphere (100 times thinner than on Earth at Sea Level), or if the dunes are the "fossil" remnants of a past epoch when the atmosphere was thicker and sand was more easily transported. This year, the Mars Orbiter Camera (MOC), onboard the Mars Global Surveyor (MGS) spacecraft, made some key observations that appear to indicate that some martian dunes are active today. In fact, some dunes probably experienced activity--wind blowing the sand around--as recently as mid-1998. Dunes typically contain granular fragments of rocks and minerals. These grains are usually 0.06 to 2 millimeters (0.002 to .08 inches)in size (which geologists call "sand"), and they are transported by the wind either by hopping over the ground (a process called "saltation") or rolling along the ground (called"traction"). Images from the Mariner 9 and Viking orbiters of the 1970s did not have sufficient resolution to see detailed patterns of sand movement, although a few Viking images showed faint streaks emanating from a few dune fields, these were interpreted as "possible" indicators of sand movement. Mars Global Surveyor has taken many images of martian dunes. Some dunes appear to be inactive and covered with dust. Other dunes, however, show all of the characteristics of fresh, active dunes. The most exciting examples have been found among the dunes in the martian north polar region. The north polar cap of Mars (shown here in mosaics of Viking Orbiter 2images 065b56 and 065b58 of regional context andlocal context )is surrounded by a zone of dark("i.e.,", estimate the rate at which sand can be transported by wind under martian conditions. Since the MOC was turned off at the end of the Science Phasing Orbits in mid-September 1998, only about seven weeks (late-July to mid-September) were available to try to repeat an observation of a north polar dune field. Only once during this short span of time was there an opportunity to cross a dune field previously observed. A north polar dune field on the floor of an old impact crater was crossed by MOC twice--once on July 30, 1998, and again on September 2, 1998. However, it turned out that the two images crossed"outside" the dune field, near the crater rim. It is quite difficult to image the same location twice with the MOC, because it cannot be pointed in a desired direction--it only "sees" what is beneath it. Minor fluctuations in the spacecraft orbit and attitude--due to variations in the martian gravity field and to upper atmosphere drag and inaccuracies within the attitude control system--led to the offset crossing. The 1998 observations of the north polar dunes and other dune fields on Mars are quite tantalizing and appear to indicate that many dunes are active under present martian conditions. Confirmation of this result will await the Mapping Phase of the MGS mission, when it should be possible to take additional pictures of the same dune fields already observed by MOC. These new pictures will be compared with the ones from 1998 to see if any changes occurred. The Mapping Phase of the MGS mission is scheduled to commence in late-March 1999, and run for an entire martian year, into March 2001. The results of the initial MOC study of martian sand dune activity are given in a paper entitled "Activity of Mars Eolian Dunes: Observation of a Low-Albedo Dune Field At High Spatial Resolution by the Mars Global Surveyor Camera," by MSSS Staff Scientist Kenneth S. Edgett and MOC Principal Investigator, Michael C. Malin, presented at the Geological Society of America Annual Meeting on October 29, 1998. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO., low albedo) dunes. These were first seen by Mariner 9 as a rippled texture, and by Viking as definitive sand dunes. Between late-July and mid-September 1998, the MGS periapsis (closest point in the spacecraft orbit relative to Mars) took the MOC right over the north polar dune fields four times a day. This provided many opportunities to take high resolution pictures of these dunes--resolutions that ranged from 1.5 to 5.0 meters (5 to 16 feet)per pixel. The very first images of these north polar dunes--one of which was released via the World Wide Web on August 7, 1998--showed that they were coated with thin, bright frost that was left-over from the northern winter season that ended in mid-July. The first images also showed small dark spots along the bases of many of the dunes. As more and higher-resolution images of the north polar dunes were taken, it became obvious that the dark spots on these dunes were areas where the seasonal frost coating had been removed--either by sublimation or by wind erosion--and that dark material was being exposed from underneath. The dark material was presumed to be the sediment that comprises the north polar dunes. Some of the dark spots have thin, dark streaks emanating from them. These dark streaks are interpreted to be the result of wind action. The simplest explanation is that gusts of wind have blown the dark sand out across the frost-covered dunes, creating a streak of deposited sand over the frost. Some spots, as in the image shown here, have multiple streaks, each one indicating a different wind gust that moved in a different direction. Because the frost that covers the north polar dunes can only be a few months old ("i.e.," northern winter lasted from mid-February 1998 to mid-July 1998), the dark streaks superposed on bright frost are clear indicators that dune material has been moved by the wind within recent months. The image shown here, MOC #50805, was taken on August 22, 1998. The streaks emanating from dark patches among the dunes in image 50805 must have formed sometime during 1998, and they most likely formed some time in July and/or August--once spring had begun in the northern hemisphere. The observation of dark spots and wind streaks among the north polar dunes led the MOC science team to attempt to image the same dunes more than once. If the dunes are indeed active, then it would be possible--it was hoped--to see changes from one image to the next. Such changes could be used to "(a)" confirm that the dunes are active and "(b)" |
|
Evidence for Recent Wind Act
…
PIA01495
Sol (our sun)
Mars Orbiter Camera
| Title |
Evidence for Recent Wind Action on Martian Sand Dunes |
| Original Caption Released with Image |
Recognizing that Mars is a desert planet, science fiction writers, scientists, and proponents of Mars exploration have, for decades, written and talked about "The Sands of Mars." The first martian sand dunes were observed by the Mariner 9 spacecraft in 1972. Ever since then, however, it has been unclear as to whether these dunes are active in today's extremely thin martian atmosphere (100 times thinner than on Earth at Sea Level), or if the dunes are the "fossil" remnants of a past epoch when the atmosphere was thicker and sand was more easily transported. This year, the Mars Orbiter Camera (MOC), onboard the Mars Global Surveyor (MGS) spacecraft, made some key observations that appear to indicate that some martian dunes are active today. In fact, some dunes probably experienced activity--wind blowing the sand around--as recently as mid-1998. Dunes typically contain granular fragments of rocks and minerals. These grains are usually 0.06 to 2 millimeters (0.002 to .08 inches)in size (which geologists call "sand"), and they are transported by the wind either by hopping over the ground (a process called "saltation") or rolling along the ground (called"traction"). Images from the Mariner 9 and Viking orbiters of the 1970s did not have sufficient resolution to see detailed patterns of sand movement, although a few Viking images showed faint streaks emanating from a few dune fields, these were interpreted as "possible" indicators of sand movement. Mars Global Surveyor has taken many images of martian dunes. Some dunes appear to be inactive and covered with dust. Other dunes, however, show all of the characteristics of fresh, active dunes. The most exciting examples have been found among the dunes in the martian north polar region. The north polar cap of Mars (shown here in mosaics of Viking Orbiter 2images 065b56 and 065b58 of regional context andlocal context )is surrounded by a zone of dark("i.e.,", estimate the rate at which sand can be transported by wind under martian conditions. Since the MOC was turned off at the end of the Science Phasing Orbits in mid-September 1998, only about seven weeks (late-July to mid-September) were available to try to repeat an observation of a north polar dune field. Only once during this short span of time was there an opportunity to cross a dune field previously observed. A north polar dune field on the floor of an old impact crater was crossed by MOC twice--once on July 30, 1998, and again on September 2, 1998. However, it turned out that the two images crossed"outside" the dune field, near the crater rim. It is quite difficult to image the same location twice with the MOC, because it cannot be pointed in a desired direction--it only "sees" what is beneath it. Minor fluctuations in the spacecraft orbit and attitude--due to variations in the martian gravity field and to upper atmosphere drag and inaccuracies within the attitude control system--led to the offset crossing. The 1998 observations of the north polar dunes and other dune fields on Mars are quite tantalizing and appear to indicate that many dunes are active under present martian conditions. Confirmation of this result will await the Mapping Phase of the MGS mission, when it should be possible to take additional pictures of the same dune fields already observed by MOC. These new pictures will be compared with the ones from 1998 to see if any changes occurred. The Mapping Phase of the MGS mission is scheduled to commence in late-March 1999, and run for an entire martian year, into March 2001. The results of the initial MOC study of martian sand dune activity are given in a paper entitled "Activity of Mars Eolian Dunes: Observation of a Low-Albedo Dune Field At High Spatial Resolution by the Mars Global Surveyor Camera," by MSSS Staff Scientist Kenneth S. Edgett and MOC Principal Investigator, Michael C. Malin, presented at the Geological Society of America Annual Meeting on October 29, 1998. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO., low albedo) dunes. These were first seen by Mariner 9 as a rippled texture, and by Viking as definitive sand dunes. Between late-July and mid-September 1998, the MGS periapsis (closest point in the spacecraft orbit relative to Mars) took the MOC right over the north polar dune fields four times a day. This provided many opportunities to take high resolution pictures of these dunes--resolutions that ranged from 1.5 to 5.0 meters (5 to 16 feet)per pixel. The very first images of these north polar dunes--one of which was released via the World Wide Web on August 7, 1998--showed that they were coated with thin, bright frost that was left-over from the northern winter season that ended in mid-July. The first images also showed small dark spots along the bases of many of the dunes. As more and higher-resolution images of the north polar dunes were taken, it became obvious that the dark spots on these dunes were areas where the seasonal frost coating had been removed--either by sublimation or by wind erosion--and that dark material was being exposed from underneath. The dark material was presumed to be the sediment that comprises the north polar dunes. Some of the dark spots have thin, dark streaks emanating from them. These dark streaks are interpreted to be the result of wind action. The simplest explanation is that gusts of wind have blown the dark sand out across the frost-covered dunes, creating a streak of deposited sand over the frost. Some spots, as in the image shown here, have multiple streaks, each one indicating a different wind gust that moved in a different direction. Because the frost that covers the north polar dunes can only be a few months old ("i.e.," northern winter lasted from mid-February 1998 to mid-July 1998), the dark streaks superposed on bright frost are clear indicators that dune material has been moved by the wind within recent months. The image shown here, MOC #50805, was taken on August 22, 1998. The streaks emanating from dark patches among the dunes in image 50805 must have formed sometime during 1998, and they most likely formed some time in July and/or August--once spring had begun in the northern hemisphere. The observation of dark spots and wind streaks among the north polar dunes led the MOC science team to attempt to image the same dunes more than once. If the dunes are indeed active, then it would be possible--it was hoped--to see changes from one image to the next. Such changes could be used to "(a)" confirm that the dunes are active and "(b)" |
|
Evidence for Recent Wind Act
…
PIA01495
Sol (our sun)
Mars Orbiter Camera
| Title |
Evidence for Recent Wind Action on Martian Sand Dunes |
| Original Caption Released with Image |
Recognizing that Mars is a desert planet, science fiction writers, scientists, and proponents of Mars exploration have, for decades, written and talked about "The Sands of Mars." The first martian sand dunes were observed by the Mariner 9 spacecraft in 1972. Ever since then, however, it has been unclear as to whether these dunes are active in today's extremely thin martian atmosphere (100 times thinner than on Earth at Sea Level), or if the dunes are the "fossil" remnants of a past epoch when the atmosphere was thicker and sand was more easily transported. This year, the Mars Orbiter Camera (MOC), onboard the Mars Global Surveyor (MGS) spacecraft, made some key observations that appear to indicate that some martian dunes are active today. In fact, some dunes probably experienced activity--wind blowing the sand around--as recently as mid-1998. Dunes typically contain granular fragments of rocks and minerals. These grains are usually 0.06 to 2 millimeters (0.002 to .08 inches)in size (which geologists call "sand"), and they are transported by the wind either by hopping over the ground (a process called "saltation") or rolling along the ground (called"traction"). Images from the Mariner 9 and Viking orbiters of the 1970s did not have sufficient resolution to see detailed patterns of sand movement, although a few Viking images showed faint streaks emanating from a few dune fields, these were interpreted as "possible" indicators of sand movement. Mars Global Surveyor has taken many images of martian dunes. Some dunes appear to be inactive and covered with dust. Other dunes, however, show all of the characteristics of fresh, active dunes. The most exciting examples have been found among the dunes in the martian north polar region. The north polar cap of Mars (shown here in mosaics of Viking Orbiter 2images 065b56 and 065b58 of regional context andlocal context )is surrounded by a zone of dark("i.e.,", estimate the rate at which sand can be transported by wind under martian conditions. Since the MOC was turned off at the end of the Science Phasing Orbits in mid-September 1998, only about seven weeks (late-July to mid-September) were available to try to repeat an observation of a north polar dune field. Only once during this short span of time was there an opportunity to cross a dune field previously observed. A north polar dune field on the floor of an old impact crater was crossed by MOC twice--once on July 30, 1998, and again on September 2, 1998. However, it turned out that the two images crossed"outside" the dune field, near the crater rim. It is quite difficult to image the same location twice with the MOC, because it cannot be pointed in a desired direction--it only "sees" what is beneath it. Minor fluctuations in the spacecraft orbit and attitude--due to variations in the martian gravity field and to upper atmosphere drag and inaccuracies within the attitude control system--led to the offset crossing. The 1998 observations of the north polar dunes and other dune fields on Mars are quite tantalizing and appear to indicate that many dunes are active under present martian conditions. Confirmation of this result will await the Mapping Phase of the MGS mission, when it should be possible to take additional pictures of the same dune fields already observed by MOC. These new pictures will be compared with the ones from 1998 to see if any changes occurred. The Mapping Phase of the MGS mission is scheduled to commence in late-March 1999, and run for an entire martian year, into March 2001. The results of the initial MOC study of martian sand dune activity are given in a paper entitled "Activity of Mars Eolian Dunes: Observation of a Low-Albedo Dune Field At High Spatial Resolution by the Mars Global Surveyor Camera," by MSSS Staff Scientist Kenneth S. Edgett and MOC Principal Investigator, Michael C. Malin, presented at the Geological Society of America Annual Meeting on October 29, 1998. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO., low albedo) dunes. These were first seen by Mariner 9 as a rippled texture, and by Viking as definitive sand dunes. Between late-July and mid-September 1998, the MGS periapsis (closest point in the spacecraft orbit relative to Mars) took the MOC right over the north polar dune fields four times a day. This provided many opportunities to take high resolution pictures of these dunes--resolutions that ranged from 1.5 to 5.0 meters (5 to 16 feet)per pixel. The very first images of these north polar dunes--one of which was released via the World Wide Web on August 7, 1998--showed that they were coated with thin, bright frost that was left-over from the northern winter season that ended in mid-July. The first images also showed small dark spots along the bases of many of the dunes. As more and higher-resolution images of the north polar dunes were taken, it became obvious that the dark spots on these dunes were areas where the seasonal frost coating had been removed--either by sublimation or by wind erosion--and that dark material was being exposed from underneath. The dark material was presumed to be the sediment that comprises the north polar dunes. Some of the dark spots have thin, dark streaks emanating from them. These dark streaks are interpreted to be the result of wind action. The simplest explanation is that gusts of wind have blown the dark sand out across the frost-covered dunes, creating a streak of deposited sand over the frost. Some spots, as in the image shown here, have multiple streaks, each one indicating a different wind gust that moved in a different direction. Because the frost that covers the north polar dunes can only be a few months old ("i.e.," northern winter lasted from mid-February 1998 to mid-July 1998), the dark streaks superposed on bright frost are clear indicators that dune material has been moved by the wind within recent months. The image shown here, MOC #50805, was taken on August 22, 1998. The streaks emanating from dark patches among the dunes in image 50805 must have formed sometime during 1998, and they most likely formed some time in July and/or August--once spring had begun in the northern hemisphere. The observation of dark spots and wind streaks among the north polar dunes led the MOC science team to attempt to image the same dunes more than once. If the dunes are indeed active, then it would be possible--it was hoped--to see changes from one image to the next. Such changes could be used to "(a)" confirm that the dunes are active and "(b)" |
|
01 January 2000 On The Red P
…
PIA02350
Sol (our sun)
Mars Orbiter Camera
| Title |
01 January 2000 On The Red Planet |
| Original Caption Released with Image |
As many people on Earth celebrated the dawn of a new year, a new century, and a new millennium, the Mars Global Surveyor(MGS) Mars Orbiter Camera (MOC) continued its journey that began with a proposal to NASA nearly 15 years earlier in 1985. As the clock rolled over to 2000 A.D., MOC was busily snapping its daily global weather maps and a variety of higher-resolution images such as the two shown here. On December 25, 1999, Mars passed its northern hemisphere winter solstice, marking the beginning of northern winter (and summer in the southern hemisphere). The pictures shown here are from the northern hemisphere among the mesas and buttes of the Nilosyrtis Mensae. This region, if it were on Earth, would be located in western Afghanistan around 33° N latitude, 63° E longitude (297°W on Mars). The picture was one of the first high resolution views of Mars taken by the MGS MOC on January 1, 2000, at 06:42 UTC (6 hours, 42 minutes after the new year began in the Greenwich Time Zone). The picture on the left is a context frame that covers an area 115 km (71 mi) across. The white box shows the location of the new millennium Mars image, which also appears on the right. This high resolution view shows a wide variety of surface textures caused mainly by unknown, possibly uniquely "martian" geologic processes. The view also includes small, bright, windblown drifts. The high resolution view covers an area 3 km across at a resolution of 4.5 meters (15 feet) per pixel. The sun illuminates both scenes from the lower left. The MGS MOC began taking pictures from Mars orbit in September 1997. It's primary mission will last through January 2001. After that, an extended mission might be approved by NASA--this would allow the camera to continue its activities well into 2002 or beyond. |
|
01 January 2000 On The Red P
…
PIA02350
Sol (our sun)
Mars Orbiter Camera
| Title |
01 January 2000 On The Red Planet |
| Original Caption Released with Image |
As many people on Earth celebrated the dawn of a new year, a new century, and a new millennium, the Mars Global Surveyor(MGS) Mars Orbiter Camera (MOC) continued its journey that began with a proposal to NASA nearly 15 years earlier in 1985. As the clock rolled over to 2000 A.D., MOC was busily snapping its daily global weather maps and a variety of higher-resolution images such as the two shown here. On December 25, 1999, Mars passed its northern hemisphere winter solstice, marking the beginning of northern winter (and summer in the southern hemisphere). The pictures shown here are from the northern hemisphere among the mesas and buttes of the Nilosyrtis Mensae. This region, if it were on Earth, would be located in western Afghanistan around 33° N latitude, 63° E longitude (297°W on Mars). The picture was one of the first high resolution views of Mars taken by the MGS MOC on January 1, 2000, at 06:42 UTC (6 hours, 42 minutes after the new year began in the Greenwich Time Zone). The picture on the left is a context frame that covers an area 115 km (71 mi) across. The white box shows the location of the new millennium Mars image, which also appears on the right. This high resolution view shows a wide variety of surface textures caused mainly by unknown, possibly uniquely "martian" geologic processes. The view also includes small, bright, windblown drifts. The high resolution view covers an area 3 km across at a resolution of 4.5 meters (15 feet) per pixel. The sun illuminates both scenes from the lower left. The MGS MOC began taking pictures from Mars orbit in September 1997. It's primary mission will last through January 2001. After that, an extended mission might be approved by NASA--this would allow the camera to continue its activities well into 2002 or beyond. |
|
The Changing South Polar Cap
…
PIA03997
Sol (our sun)
Mars Orbiter Camera
| Title |
The Changing South Polar Cap of Mars: 1999-2005 |
| Original Caption Released with Image |
13 July 2005 The south polar residual cap of Mars is composed of layered, frozen carbon dioxide. In 1999, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) showed that the carbon dioxide layers have been eroded to form a variety of circular pits, arcuate scarps, troughs, buttes, and mesas. In 2001, MOC images designed to provide repeated views of the areas imaged in 1999 -- with the hope of creating stereo (3-D) images, so that the height of scarps and depth of pits could be measured -- showed that the scarps had retreated, pits enlarged, and buttes and mesas shrank. Only carbon dioxide is volatile enough in the martian environment to have caused such dramatic changes -- the scarps were seen to retreat at an average rate of 3 meters (about 3 yards) per Mars year. Most of the scarp retreat occurs during the southern summer season, in some areas the scarps move as much as 8 meters, in others, only 1 meter per Mars year. Three Mars years have now elapsed since MOC first surveyed the south polar cap in 1999. Over the past several months, MGS MOC has been re-imaging areas that were seen in 1999, 2001, and 2003, to develop a detailed look at how the landscape has been changing. This animated GIF provides an example of the dramatic changes that have occurred during the past three martian years. The first image, a sub-frame of M09-05244, was acquired on 21 November 1999. The second image, a sub-frame of S06-00973, was obtained on 11 May 2005. The animation shows the changes that have occurred between 1999 and 2005. Each summer, the cap has lost more carbon dioxide. This may mean that the carbon dioxide content of the martian atmosphere has been increasing, bit by very tiny little bit, each of the years that MGS has been orbiting the red planet. These observations also imply that there was once a time, in the not-too-distant past (because there are no impact craters on the polar cap), when the atmosphere was somewhat thinner and colder, to permit the layers of carbon dioxide to form in the first place. Just as Earth's environment is very different today than it was just 11,000 or so years ago, the martian environment has also been changing on a similar time scale. "Location near": 88.9°S, 25.7°W "Image width": width: ~0.6 km (~0.4 mi) "Illumination from": upper left "Season": Southern Spring |
|
MOC Observes Changes in the
…
PIA03179
Sol (our sun)
Mars Orbiter Camera
| Title |
MOC Observes Changes in the South Polar Cap: Evidence for Recent Climate Change on Mars |
| Original Caption Released with Image |
Compare each image on the left with their counterparts on the right. Small hills vanished and pit walls expanded between 1999 and 2001. The pits are formed in frozen carbon dioxide, and the carbon dioxide is subliming away a little more each Martian year. Sunlight illuminates each of the four different scenes from the upper left. CLICK HERE, deposited. The martian climate was probably colder, and there was more carbon dioxide in the atmosphere. For some reason, large amounts of carbon dioxide froze at the south pole--one might say that there was a "Martian Ice Age"--and this freezing occurred on a time scale similar to that of the most recent Ice Age on Earth. Mars is changing, and it is changing on a time scale that we can measure and observe. If all of the carbon dioxide that is being released into the atmosphere from the south polar cap is not freezing out somewhere else, and if it is not being adsorbed into the martian soil, then it must be causing the atmospheric pressure to increase. If this so, and if one were to assume that the entire known volume of the polar cap is made of carbon dioxide that sublimes at the same rate we see today, then it could increase the martian atmospheric pressure by as much as 10 times, to about 1/10th the density of Earth's atmosphere, in just the next few thousand years. Although this atmosphere would not be breathable, carbon dioxide is a "greenhouse gas" that would cause the global temperature to increase considerably and make it easier for liquid water to persist elsewhere on the planet. Perhaps, just perhaps, a thickening martian atmosphere would eventually make it easier for people to live on Mars., for animation of all 4 of these panels (6.2 MBytes). One of the most profound benefits of being able to continue photographing Mars in the Mars Global Surveyor (MGS) Extended Mission is the opportunity to go back and re-image a site that was seen in the previous martian year. New MGS Mars Orbiter Camera (MOC)images have provided a startling observation: The residual martian south polar cap is changing. The fact that it is changing suggests that Mars may have major, global climate changes that are occurring on the same time scales as Earth's most recent climate shifts, including the last Ice Age. MOC images of the south polar cap taken in 1999 were compared with images of the same locations taken in 2001, and it was discovered that pits had enlarged, mesas had shrunk, and small buttes had vanished. In all, the scarps that enclose the pits and bound the mesas and buttes retreated about 3 meters (3.3 yards) in 1 martian year (687 Earth days). This rapid retreat of polar scarps can only occur if the ice is frozen carbon dioxide (also known as "dryice"). Retreat of scarps made of water ice is much slower and would not have been measurable from one martian year to the next. The portion of the martian south polar cap that persists through summer is called the residual polar cap. The two sets of four pictures shown here are from four places on the residual south polar cap. The pictures from 1999 were taken in October of that year, the corresponding pictures from 2001 were acquired in August, approximately 1 Mars year after the 1999 images were obtained. In each case, the pictures are illuminated by sunlight from the upper left, and each shows an area about 250 meters (273 yards) across. The polarcap is layered, and the layers have eroded to form pits, troughs, mesas, and buttes. The pits form as sunlight warms frozen carbon dioxide during southern spring and summer, and the ice sublimes away. There is so much carbon dioxide that it does not all go away in one summer--in fact, it may take hundreds to thousands of years to disappear. These new observations indicate that the south polar residual cap is not permanent. It is disappearing, a little bit more each southern spring and summer season. At the present rate, a layer 3 m thick can be completely eroded away in a few tens of martian years. Since each layer is equivalent to about 1% of the mass of the present atmosphere (which is 95% carbon dioxide), if sufficient carbon dioxide is buried in the south polar cap, the mass of the atmosphere could double in a few hundred to a thousand Mars years. That could lead to profound changes in the environment. For example, it would change how much and where wind erosion would occur, and where and for how long liquid water could survive at or near the surface. It also means that Mars may have been very different in the recent past (perhaps only a few thousands of years ago). On today's Mars, the ice is eroding, but in the past that material had to have been |
|
MOC Observes Changes in the
…
PIA03179
Sol (our sun)
Mars Orbiter Camera
| Title |
MOC Observes Changes in the South Polar Cap: Evidence for Recent Climate Change on Mars |
| Original Caption Released with Image |
Compare each image on the left with their counterparts on the right. Small hills vanished and pit walls expanded between 1999 and 2001. The pits are formed in frozen carbon dioxide, and the carbon dioxide is subliming away a little more each Martian year. Sunlight illuminates each of the four different scenes from the upper left. CLICK HERE, deposited. The martian climate was probably colder, and there was more carbon dioxide in the atmosphere. For some reason, large amounts of carbon dioxide froze at the south pole--one might say that there was a "Martian Ice Age"--and this freezing occurred on a time scale similar to that of the most recent Ice Age on Earth. Mars is changing, and it is changing on a time scale that we can measure and observe. If all of the carbon dioxide that is being released into the atmosphere from the south polar cap is not freezing out somewhere else, and if it is not being adsorbed into the martian soil, then it must be causing the atmospheric pressure to increase. If this so, and if one were to assume that the entire known volume of the polar cap is made of carbon dioxide that sublimes at the same rate we see today, then it could increase the martian atmospheric pressure by as much as 10 times, to about 1/10th the density of Earth's atmosphere, in just the next few thousand years. Although this atmosphere would not be breathable, carbon dioxide is a "greenhouse gas" that would cause the global temperature to increase considerably and make it easier for liquid water to persist elsewhere on the planet. Perhaps, just perhaps, a thickening martian atmosphere would eventually make it easier for people to live on Mars., for animation of all 4 of these panels (6.2 MBytes). One of the most profound benefits of being able to continue photographing Mars in the Mars Global Surveyor (MGS) Extended Mission is the opportunity to go back and re-image a site that was seen in the previous martian year. New MGS Mars Orbiter Camera (MOC)images have provided a startling observation: The residual martian south polar cap is changing. The fact that it is changing suggests that Mars may have major, global climate changes that are occurring on the same time scales as Earth's most recent climate shifts, including the last Ice Age. MOC images of the south polar cap taken in 1999 were compared with images of the same locations taken in 2001, and it was discovered that pits had enlarged, mesas had shrunk, and small buttes had vanished. In all, the scarps that enclose the pits and bound the mesas and buttes retreated about 3 meters (3.3 yards) in 1 martian year (687 Earth days). This rapid retreat of polar scarps can only occur if the ice is frozen carbon dioxide (also known as "dryice"). Retreat of scarps made of water ice is much slower and would not have been measurable from one martian year to the next. The portion of the martian south polar cap that persists through summer is called the residual polar cap. The two sets of four pictures shown here are from four places on the residual south polar cap. The pictures from 1999 were taken in October of that year, the corresponding pictures from 2001 were acquired in August, approximately 1 Mars year after the 1999 images were obtained. In each case, the pictures are illuminated by sunlight from the upper left, and each shows an area about 250 meters (273 yards) across. The polarcap is layered, and the layers have eroded to form pits, troughs, mesas, and buttes. The pits form as sunlight warms frozen carbon dioxide during southern spring and summer, and the ice sublimes away. There is so much carbon dioxide that it does not all go away in one summer--in fact, it may take hundreds to thousands of years to disappear. These new observations indicate that the south polar residual cap is not permanent. It is disappearing, a little bit more each southern spring and summer season. At the present rate, a layer 3 m thick can be completely eroded away in a few tens of martian years. Since each layer is equivalent to about 1% of the mass of the present atmosphere (which is 95% carbon dioxide), if sufficient carbon dioxide is buried in the south polar cap, the mass of the atmosphere could double in a few hundred to a thousand Mars years. That could lead to profound changes in the environment. For example, it would change how much and where wind erosion would occur, and where and for how long liquid water could survive at or near the surface. It also means that Mars may have been very different in the recent past (perhaps only a few thousands of years ago). On today's Mars, the ice is eroding, but in the past that material had to have been |
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The Martian North Polar Cap
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PIA03204
Sol (our sun)
Mars Orbiter Camera
| Title |
The Martian North Polar Cap in Summer - One Year Later |
| Original Caption Released with Image |
In the middle of January 2001, Mars Global Surveyor (MGS) completed one Mars year in its ~380 km-high (236 mi) mapping orbit. The mapping orbit was originally achieved in late February 1999. In March of that year, MGS conducted a series of operations in preparation for full-up mapping, first calibrating its scientific instruments and then operating in a mode in which the high gain antenna was held fixed against the body of the spacecraft. During this Fixed High Gain Antenna period, "contingency science" observations were made in case the high gain antenna failed to properly deploy. The wide angle view of the martian north polar cap shown on the left was acquired on March 13, 1999, during early northern summer. The image on the right was acquired almost exactly one Mars year later, on January 26, 2001. The light-toned surfaces are residual water ice that remains through the summer season. The nearly circular band of dark material surrounding the cap consists mainly of sand dunes formed and shaped by wind. The north polar cap is roughly 1100 kilometers (680 miles) across. Close inspection will show that there are differences in the frost cover between the two images (for example, in the upper center of each image, and on the left edge center). Although these changes appear small, they are in fact quite large--the change in frost covering is equivalent to the amount of frost that would be evaporated (in the case of areas that are darker) or deposited (in areas where frost is still on the ground) in almost 5 months. What gives rise to such large changes in the heat budget for the polar caps from one year to the next is not known. Changes in the coloration and brightness of the polar cap suggest dust, deposited perhaps by dust storms during critical periods of the year, may play an important role. |
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Mid-Latitude Sedimentary Roc
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PIA03203
Sol (our sun)
Mars Orbiter Camera
| Title |
Mid-Latitude Sedimentary Rock: Spallanzani Crater |
| Original Caption Released with Image |
Although most of the best examples of layered sedimentary rock seen on Mars are found at equatorial and sub-tropical latitudes, a few locations seen at mid- and high-latitudes suggest that layered rocks are probably more common than we can actually see from orbit. One extremely good example of these "atypical" layered rock exposures is found in the 72 km-diameter (45 miles) crater, Spallanzani (58.4°S, 273.5°W). Located southeast of Hellas Planitia, the crater is named for the 18th Century Italian biologist, Lazzaro Spallanzani (1729-1799). Picture A presents a composite of the best Viking orbiter image (VO2-504B55) of the region with 4 pictures obtained June 1999 through January 2001 by the Mars Global Surveyor Mars Orbiter Camera (MOC). Each MOC narrow angle image is 3 km across. Taken in the MOC's "survey mode," all four images were acquired at roughly 12 meters (39 ft) per pixel. Picture B zooms-in on the portion of the composite image that includes the 4 MOC images (the 100%-size view is 20 m (66 ft) per pixel). Other craters in the region near Spallanzani show features--at Viking Orbiter scale--that are reminiscent of the layering seen in Spallanzani. Exactly what these layers are made of and how they came to be where we see them today are mysteries, but it is possible that they are similar to the materials seen in the many craters and chasms of the equatorial latitudes on Mars. |
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Mid-Latitude Sedimentary Roc
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PIA03203
Sol (our sun)
Mars Orbiter Camera
| Title |
Mid-Latitude Sedimentary Rock: Spallanzani Crater |
| Original Caption Released with Image |
Although most of the best examples of layered sedimentary rock seen on Mars are found at equatorial and sub-tropical latitudes, a few locations seen at mid- and high-latitudes suggest that layered rocks are probably more common than we can actually see from orbit. One extremely good example of these "atypical" layered rock exposures is found in the 72 km-diameter (45 miles) crater, Spallanzani (58.4°S, 273.5°W). Located southeast of Hellas Planitia, the crater is named for the 18th Century Italian biologist, Lazzaro Spallanzani (1729-1799). Picture A presents a composite of the best Viking orbiter image (VO2-504B55) of the region with 4 pictures obtained June 1999 through January 2001 by the Mars Global Surveyor Mars Orbiter Camera (MOC). Each MOC narrow angle image is 3 km across. Taken in the MOC's "survey mode," all four images were acquired at roughly 12 meters (39 ft) per pixel. Picture B zooms-in on the portion of the composite image that includes the 4 MOC images (the 100%-size view is 20 m (66 ft) per pixel). Other craters in the region near Spallanzani show features--at Viking Orbiter scale--that are reminiscent of the layering seen in Spallanzani. Exactly what these layers are made of and how they came to be where we see them today are mysteries, but it is possible that they are similar to the materials seen in the many craters and chasms of the equatorial latitudes on Mars. |
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Mid-Latitude Sedimentary Roc
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PIA03203
Sol (our sun)
Mars Orbiter Camera
| Title |
Mid-Latitude Sedimentary Rock: Spallanzani Crater |
| Original Caption Released with Image |
Although most of the best examples of layered sedimentary rock seen on Mars are found at equatorial and sub-tropical latitudes, a few locations seen at mid- and high-latitudes suggest that layered rocks are probably more common than we can actually see from orbit. One extremely good example of these "atypical" layered rock exposures is found in the 72 km-diameter (45 miles) crater, Spallanzani (58.4°S, 273.5°W). Located southeast of Hellas Planitia, the crater is named for the 18th Century Italian biologist, Lazzaro Spallanzani (1729-1799). Picture A presents a composite of the best Viking orbiter image (VO2-504B55) of the region with 4 pictures obtained June 1999 through January 2001 by the Mars Global Surveyor Mars Orbiter Camera (MOC). Each MOC narrow angle image is 3 km across. Taken in the MOC's "survey mode," all four images were acquired at roughly 12 meters (39 ft) per pixel. Picture B zooms-in on the portion of the composite image that includes the 4 MOC images (the 100%-size view is 20 m (66 ft) per pixel). Other craters in the region near Spallanzani show features--at Viking Orbiter scale--that are reminiscent of the layering seen in Spallanzani. Exactly what these layers are made of and how they came to be where we see them today are mysteries, but it is possible that they are similar to the materials seen in the many craters and chasms of the equatorial latitudes on Mars. |
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Defrosting Sand Dunes in Lat
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PIA03227
Sol (our sun)
| Title |
Defrosting Sand Dunes in Late Southern Winter |
| Original Caption Released with Image |
As winter gives way to spring in the martian southern hemisphere, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) is observing the retreat of the south polar frost cap as sunlight falls upon it for the first time in several months. One of the most aesthetically-pleasing aspects of the spring defrosting process is the pattern that is created on the martian sand dune fields. Dunes are usually among the first surfaces to begin showing signs of change in late winter when temperatures are just beginning to creep above -125° C (-193° F, 148 K). The pattern of spots on the dunes in the above MOC picture was observed on June 8, 2001. The location of the dune field is near 62°S, 155°W. Dark spots and streaks on defrosting sand dunes were first observed by MOC in the northern hemisphere in 1998 [ http://www.msss.com/mars_images/moc/8_7_98_n_erg_rel/ ]. Similar dark-spotted dunes in the southern hemisphere were described at a NASA/Mars Global Surveyor Space Science Update media briefing in 1999 [ http://www.msss.com/mars_images/moc/8_10_99_releases/ ]. Despite the "sensation" one gets when looking at pictures of spotted, defrosting martian dunes (i.e., the sensation that these images show some form of life, like vegetation, growing on Mars) these features are a normal, common manifestation of the springtime defrosting process on Mars. The ices involved--because of the low temperatures at these locations--are probably both frozen water and carbon dioxide, though it is unclear as to whether one type of ice dominates over the other in controlling the appearance and coalescence of the dark spots. It is known from the first martian year of MOC operations that by summer all of the frost--and thus all of the spots--on the dunes will be gone. North is up and sunlight illuminates the scene from the upper left in both pictures. The color context view covers an area approximately 115 km (72 miles) across, the high resolution image covers 3 km by 22 km (1.9by 13.6 mi). |
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Changes Over a Martian Year
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PIA03226
Sol (our sun)
Mars Orbiter Camera
| Title |
Changes Over a Martian Year -- New Dark Slope Streaks in Lycus Sucli |
| Original Caption Released with Image |
Now in its Extended Mission, Mars Global Surveyor (MGS) is into its second Mars year of systematic observations of the red planet. With the Extended Mission slated to run through April 2002, the Mars Orbiter Camera (MOC) is being used, among other things, to look for changes that have occurred in the past martian year. Because Mars is farther from the Sun than Earth, its year is longer--about 687 Earth days. The two pictures shown here cover the same portion of Lycus Sulci, a rugged, ridged terrain north of the giant Olympus Mons volcano. The interval between the pictures span 92% of a martian year (August 2, 1999 to April 27, 2001). Dark streaks considered to result from the avalanching of dry, fine, bright dust are seen in both images. The disruption of the surface by the avalanching materials is thought to cause them to appear darker than their surroundings, just as the 1997 bouncing of Mars Pathfinder's airbags and the tire tracks made by the Sojourner rover left darkened markings indicating where the martian soil had been disrupted and disturbed. The arrows in the April 2001 picture indicate eight new streaks that formed on these slopes in Lycus Sulci since August 1999. These observations suggest that a new streak forms approximately once per martian year per kilometer (about 0.62 miles) along a slope. In both images, north is toward the top/upper right and sunlight illuminates each from the left. Dark (as well bright) slope streaks are most common in the dust-covered martian regions of Tharsis, Arabia, and Elysium. |
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Mid-Winter Dust Storms Near
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PIA03222
Sol (our sun)
Mars Orbiter Camera
| Title |
Mid-Winter Dust Storms Near Hellas Planitia |
| Original Caption Released with Image |
One of the primary objectives for the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during the Extended Mission is to continue daily monitoring of martian weather as expressed in clouds, dust storms, and patches of polar frost. During the Primary Mission, which lasted from March 1999 through January 2001, changes that occurred over a single martian year (687 Earth days) were observed. Now it is possible to see what the martian atmosphere will do for at least two-thirds of a second martian year, because the Extended Mission will run into April 2002. This picture captures two dust storms, each large enough to cover Arizona or New Mexico. One is located near the lower left, the other at the lower right. Taken on April 8, 2001 (mid-southern winter), this is a mosaic of six MOC daily global images centered around Hellas Planitia in the martian southern hemisphere. Hellas Planitia is the dominant elliptical feature just below the center of the picture. The bright, nearly white surfaces along the lower (southern) edge of the picture are covered by wintertime frost. The strong temperature difference between the winter frost and the warmer air just off the edge of this polar cap generates winds that--at this time of year--are often strong enough to lift dust into large, reddish-brown, billowy clouds. North is up and sunlight illuminates the area from the upper left. The martian equator forms the arc along the top of the picture, 500 kilometers (km) is equal to about 311 miles. The approximately 500 kilometer-wide circular feature just above the center is the crater Huygens. |
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Sand Dunes of Nili Patera in
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PIA03224
Sol (our sun)
Mars Orbiter Camera
| Title |
Sand Dunes of Nili Patera in 3-D |
| Original Caption Released with Image |
The most exciting new aspect of the Mars Global Surveyor (MGS) Extended Mission is the opportunity to turn the spacecraft and point the Mars Orbiter Camera (MOC) at specific features of interest. Opportunities to point the spacecraft come about ten times a week. Throughout the Primary Mission (March 1999 - January 2001), nearly all MGS operations were conducted with the spacecraft pointing "nadir"--that is, straight down. A search for the missing Mars Polar Lander in late 1999 and early 2000 demonstrated that pointing the spacecraft could allow opportunities for MOC to see things that simply had not entered its field of view during typical nadir-looking operations, and to target areas previously seen in a nadir view so that stereo ("3-D") pictures could be derived. One of the very first places photographed by the MOC at the start of the Mapping Mission in March 1999 was a field of dunes located in Nili Patera, a volcanic depression in central Syrtis Major. A portion of this dune field was shown in a media release on March 11, 1999, "Sand Dunes of Nili Patera, Syrtis Major". Subsequently, the image was archived with the NASA Planetary Data System, as shown in the Malin Space Science Systems MOC Gallery. On April 24, 2001, an opportunity arose in which the MGS could be pointed off-nadir to take a new picture of the same dune field. By combining the nadir view from March 1999 and the off-nadir view from April 2001, a stereoscopic image was created. The anaglyph shown here must be viewed with red (left-eye) and blue (right-eye) "3-D" glasses. The dunes and the local topography of the volcanic crater's floor stand out in sharp relief. The images, taken more than one Mars year apart, show no change in the shape or location of the dunes--that is, they do not seem to have moved at all since March 1999. |
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Highest-Resolution View of "
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PIA03225
Sol (our sun)
Mars Orbiter Camera
| Title |
Highest-Resolution View of "Face on Mars |
| Original Caption Released with Image |
A key aspect of the Mars Global Surveyor (MGS) Extended Mission is the opportunity to turn the spacecraft and point the Mars Orbiter Camera (MOC) at specific features of interest. A chance to point the spacecraft comes about ten times a week. Throughout the Primary Mission (March 1999 - January 2001), nearly all MGS operations were conducted with the spacecraft pointing "nadir"--that is, straight down. In this orientation, opportunities to hit a specific small feature of interest were in some cases rare, and in other cases non-existent. In April 1998, nearly a year before MGS reached its Primary Mission mapping orbit, several tests of the spacecraft's ability to be pointed at specific features was conducted with great success (e.g., Mars Pathfinder landing site, Viking 1 site, and Cydonia landforms). When the Mars Polar Lander was lost in December 1999, this capability was again employed to search for the missing lander. Following the lander search activities, a plan to conduct similar off-nadir observations during the MGS Extended Mission was put into place. The Extended Mission began February 1, 2001. On April 8, 2001, the first opportunity since April 1998 arose to turn the spacecraft and point the MOC at the popular "Face on Mars" feature. Viking orbiter images acquired in 1976 showed that one of thousands of buttes, mesas, ridges, and knobs in the transition zone between the cratered uplands of western Arabia Terra and the low, northern plains of Mars looked somewhat like a human face. The feature was subsequently popularized as a potential "alien artifact" in books, tabloids, radio talk shows, television, and even a major motion picture. Given the popularity of this landform, a new high-resolution view was targeted by pointing the spacecraft off-nadir on April 8, 2001. On that date at 20:54 UTC (8:54 p.m., Greenwich time zone), the MGS was rolled 24.8° to the left so that it was looking at the "face" 165 km to the side from a distance of about 450 km. The resulting image has a resolution of about 2 meters (6.6 feet) per pixel. If present on Mars, objects the size of typical passenger jet airplanes would be distinguishable in an image of this scale. The large "face" picture covers an area about 3.6 kilometers (2.2 miles) on a side. Sunlight illuminates the images from the left/lower left. |
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Fresh Impact Crater and Rays
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PIA03469
Sol (our sun)
Mars Orbiter Camera
| Title |
Fresh Impact Crater and Rays in Tharsis |
| Original Caption Released with Image |
Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO., The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) Extended Mission has included dozens of opportunities to point the spacecraft directly at features of interest so that pictures of things not seen during the earlier Mapping Mission can be obtained. The example shown here is a small meteorite impact crater in northern Tharsis near 17.2°N, 113.8°W. Viking Orbiter images from the late 1970's showed at this location what appeared to be a dark patch with dark rays emanating from a brighter center. The MOC team surmised that the dark rays may be indicating the location of afresh crater formed by impact sometime in the past few centuries (since dark ray are quickly covered by dust falling out of the martian atmosphere). All through MOC's Mapping Mission in 1999 and 2000, attempts were made to image the crater as predictions indicated that the spacecraft would pass over the site, but the crater was never seen. Finally, in June 2001, Extended Mission operations allowed the MOC team to point the spacecraft (and hence the camera, which is fixed to the spacecraft)directly at the center of the dark rays, where we expected to find the crater. The picture on the left (above, A) is a mosaic of three MOC high resolution images and one much lower-resolution Viking image. From left to right, the images used in the mosaic are: Viking 1 516A55, MOC E05-01904, MOCM21-00272, and MOC M08-03697. Image E05-01904 is the one taken in June 2001 by pointing the spacecraft. It captured the impact crater responsible for the rays. A close-up of the crater, which is only 130 meters (427 ft)across, is shown on the right (above, B). This crater is only one-tenth the size of the famous Meteor Crater in northern Arizona. The June 2001 MOC image reveals many surprises about this feature. For one, the crater is not located at the center of the bright area from which the dark rays radiate. The rays point to the center of this bright area, not the crater. Further, the dark material ejected from the crater--immediately adjacent to the crater rim in the picture on the right (above, B)--is not continuously connected to the larger pattern of rays. Asymmetries in crater form and ejecta patterns are generally believed to occur when the impact is oblique to the surface. The offset of the crater from the center of the rays suggests that the meteor struck at an angle, most likely from the bottom/lower right (south/southeast). The strange geometry of the rays is quite different from that seen for rays associated with impact craters on the Moon and other airless bodies, one possible explanation is that they resulted from disruption of dust on the martian surface by winds generated by the shock wave as the meteor plunged through the martian atmosphere before it struck the ground. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet |
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MGS MOC Extended Mission Vie
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PIA03468
Sol (our sun)
Mars Orbiter Camera
| Title |
MGS MOC Extended Mission View of North Polar Layers |
| Original Caption Released with Image |
The north polar cap of Mars is the only place on the surface of the planet that is known to have water. Of course, the water there is frozen. Unfortunately, the martian north polar cap has been a difficult place for the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) to view. Each winter, the pole spends approximately 6 months in darkness. Each spring, everything is covered with frost. In summer and through autumn, the cap is often obscured by clouds--sometimes clouds of dust from raging dust storms, and sometimes clouds of water ice crystals. However, a period of excellent viewing conditions occurred early in the MGS Extended Mission (from February through April 2001). This image, taken by MOC in April 2001, shows the layers comprising the north polar cap exposed in an arcuate scarp that occurs at one end of Chasma Boreale. MOC images acquired in 1999 showed that the polar cap has two types of layers: there is a stack of light-toned, nearly uniformly-bedded layers at the top, and a stack of darker-toned beds that form shelves and benches at the bottom. The darker, lower beds are older. Dozens of MOC images were targeted during the clear-atmosphere period in 2001 to test the MOC team's hypotheses about the polar cap layers and these images have helped in documenting the nature of these layers. The lower, dark layers of the polar cap appear to include considerable amounts of sand, while the upper layers lack sand and instead may be a mixture of ice and dust. The lower layers appear to contributes and to the dune fields that surround the polar cap, though no dunes are present in the image shown here. This image is illuminated from the lower right and covers an area 14.5 km (9 mi.) across. The scarp slopes toward the bottom of the scene. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO. |
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Changes in South Polar Carbo
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PIA03471
Sol (our sun)
Mars Orbiter Camera
| Title |
Changes in South Polar Carbon Dioxide Ice Cap |
| Original Caption Released with Image |
Extended mission operations for the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has provided thousands of opportunities to image sites previously seen by the camera. Often, these are chances to see if anything on the planet has changed. The most surprising changes were documented starting in August 2001, when the south polar cap emerged from winter darkness. In 1999 MOC found that the south polar cap exhibits an array of bizarre layers, arcuate scarps, and "swiss cheese" holes and pits. How these formed was unknown. Once MOC began to re-image these areas in 2001, however, the team discovered that the polar scarps had changed. They had retreated approximately 3 meters (about 3 yards) in less than 1 Mars year(a Mars year is 687 Earth days long). In some places, small buttes completely disappeared (e.g., see arrow). In December 2001, MOC scientists reported that such rapid change could only have occurred if the south polar cap is composed mainly of frozen carbon dioxide. The image on the left, above, was taken on November 28, 1999. The picture on the right was obtained nearly 1 Mars year later on October 9, 2001. Both images are illuminated from the upper right and each covers an area 2 km (1.2 mi.)wide by 6.9 km (4.3 mi.) long. Since the initial discovery of scarp retreat in the south polar cap in August 2001, MOC Extended Mission operations have included observation of many changes that occurred since 1999, and acquisition of new data to see how the cap changes from Spring in late 2001 through Summer in early 2002. Additional images have been obtained to help document changes when the polar cap returns to Spring in 2003. Previous releases regarding changes in south polar cap Carbon Dioxide landforms: * MOC Observes Changes in the South Polar Cap: Evidence for Recent Climate Change on Mars: PIA03179 [ http://photojournal.jpl.nasa.gov/catalog/PIA03179 ] * MOC View of the Martian South Polar Residual Cap: PIA03180 [ http://photojournal.jpl.nasa.gov/catalog/PIA03180 ] Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO. |
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Moon/Mars Landing Commemorat
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PIA01454
Sol (our sun)
Mars Orbiter Camera
| Title |
Moon/Mars Landing Commemorative Release: Gusev Crater and Ma'adim Vallis |
| Original Caption Released with Image |
(NASA SP-530), that included Gusev Crater as a possible priority site for future Mars exploration because it might once have been a lake. At 12:17 a.m. (PDT) on April 24, 1998-- during Mars Global Surveyor's 259th orbit--MOC obtained the high resolution image of Gusev Crater and Ma'adim Vallis shown above, in part to test some of the proposed hypotheses. The raw image has a scale of 7.3 meters (24 feet) per pixel. At this scale, there are no obvious shorelines that would indicate the past presence of a lake in either Ma'adim Vallis or Gusev Crater. There are several alternative explanations for this absence, including: * It is possible that any lake in Gusev occurred so long ago that erosion by wind and hillslope processes have long since removed such features. * It is possible that 7.3 meters per pixel is insufficient to identify key diagnostic lake features. * It is possible that a lake once existed, but that shore- and near-shore processes as they occur in terrestrial lake environments did not occur on Mars. * It is possible no lake ever existed. When Mars Global Surveyor achieves its Mapping Orbit in March 1999, MOC will have the ability to obtain pictures with resolutions around 1.5 meters (5 feet) per pixel. Sometime during the mapping mission, it may be possible to image Gusev Crater again to look for potential lake features and possible future landing sites. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO., On July 20, 1969, the first human beings landed on the Moon. On July 20, 1976, the first robotic lander touched down on Mars. This July 20th-- 29 years after Apollo 11 and 22 years since the Viking 1 Mars landing-- we take a look forward toward one possible future exploration site on the red planet. One of the advantages of the Mars Global Surveyor Mars Orbiter Camera (MOC) over its predecessors on the Viking and Mariner spacecraft is resolution. The ability to see"-- resolve--"fine details on the martian surface is key to planning future landing sites for robotic and, perhaps, human explorers that may one day visit the planet. At present, NASA is studying potential landing sites for the Mars Surveyor landers, rovers, and sample return vehicles that are scheduled to be launched in 2001, 2003, and 2005. Among the types of sites being considered for these early 21st Century landings are those with "exobiologic potential"--that is, locations on Mars that are in some way related to the past presence of water. For more than a decade, two of the prime candidates suggested by various Mars research scientists are Gusev Crater and Ma'adim Vallis. Located in the martian southern cratered highlands at 14.7° S, 184.5° W, Gusev Crater is a large, ancient, meteor impact basin that--after it formed--was breached by Ma'adim Vallis. Viking Orbiter observations provided some evidence to suggest that a fluid--most likely, water--once flowed through Ma'adim Vallis and into Gusev Crater. Some scientists have suggested that there were many episodes of flow into Gusev Crater (as well as flow out of Gusev through its topographically-lower northwestern rim). Some have also indicated that there were times when Ma'adim Vallis, also, was full of water such that it formed a long, narrow lake. The possibility that water flowed into Gusev Crater and formed a lake has led to the suggestion that the materials seen on the floor of this crater--smooth-surfaced deposits, buried craters, and huge mesas near the mouth of Ma'adim Vallis--are composed of sediment that eroded out of the highlands to the south of Gusev Crater. In 1995, the Exobiology Program Office at NASA Headquarters produced a report, "An Exobiological Strategy for Mars Exploration" |
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