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NASA's Mars Team Teaches Old …

Animated route of Spirit's e …

1/2/07

3 Years on Mars: Opportunity

Overview of Mars Exploration …

1/24/07

Cape Verde, Mars

This Mars Exploration Rover …

4/1/08

Description	This Mars Exploration Rover Opportunity Pancam "super resolution" mosaic of the approximately 6 meter (20 foot) high cliff face of the Cape Verde promontory was taken by the rover from inside Victoria Crater, during the rover's descent into Duck Bay. Super-resolution is an imaging technique that utilizes information from multiple pictures of the same target in order to generate an image with a higher resolution than any of the individual images. Cape Verde is a geologically rich outcrop and is teaching scientists about how rocks at Victoria crater were modified since they were deposited long ago. This image complements super resolution mosaics obtained at Cape St. Mary and Cape St. Vincent and is consistent with the hypothesis that Victoria crater is located in the middle of what used to be an ancient sand dune field. This image was acquired on sols 1342 and 1356 (Nov. 2 and 17, 2007). Image Credit: NASA/JPL-Caltech/Cornell University
Date	4/1/08

Gullies at the Edge of Hale Crater, Mars

Gullies at the Edge of Hale …

This image from NASA's Mars …

10/6/09

Description	This image from NASA's Mars Reconnaissance Orbiter shows gullies near the edge of Hale crater on southern Mars. Martian gullies carved into hill slopes and the walls of impact craters were discovered several years ago. On Earth, gullies usually form through the action of liquid water -- long thought to be absent on the Martian surface. Whether liquid water carves gullies under today's cold and dry conditions on Mars is a major question that planetary scientists are trying to answer. Gullies at this site are especially interesting because scientists recently discovered actively changing examples at similar locations. Images separated by several years showed changes in the appearance of some of these gullies. Today, planetary scientists are using the HiRISE camera on MRO to examine gullies such as the one in this image for change that might provide a clue about whether liquid water occurs on the surface of Mars. The view covers an area about 1 kilometer, or 0.6 mile, across and was taken on Aug. 3, 2009. Image Credit: NASA/JPL-Caltech/University of Arizona
Date	10/6/09

Dunes of Mars

Dunes of sand-sized material …

01/21/10

Description	Dunes of sand-sized materials have been trapped on the floors of many Martian craters. This is one example, from a crater in Noachis Terra, west of the giant Hellas impact basin. The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter captured this view on Dec. 28, 2009. The dunes here are linear, thought to be due to shifting wind directions. In places, each dune is remarkably similar to adjacent dunes, including a reddish (or dust colored) band on northeast-facing slopes. Large angular boulders litter the floor between dunes. Image Credit: NASA/JPL-Caltech/University of Arizona
Date	01/21/10

NASA SCI Files - Mars

NASA Sci Files segment explo …

5/14/03

Description	NASA Sci Files segment exploring Mars and how it is similar and different than the Earth.
Date	5/14/03

Giant Landslide on Iapetus

Description	Giant Landslide on Iapetus
Full Description	A spectacular landslide within the low-brightness region of Iapetus's surface known as Cassini Regio is visible in this image from Cassini. Iapetus is one of the moons of Saturn. The landslide material appears to have collapsed from a scarp 15 kilometers high (9 miles) that forms the rim of an ancient 600 kilometer (375 mile) impact basin. Unconsolidated rubble from the landslide extends halfway across a conspicuous, 120-kilometer diameter (75-mile) flat-floored impact crater that lies just inside the basin scarp. Landslides are common geological phenomena on many planetary bodies, including Earth and Mars. The appearance of this landslide on an icy satellite with low-brightness cratered terrain is reminiscent of landslide features that were observed during NASA's Galileo mission on the Jovian satellite Callisto. The fact that the Iapetus landslide traveled many kilometers from the basin scarp could indicate that the surface material is very fine-grained, and perhaps was fluffed by mechanical forces that allowed the landslide debris to flow extended distances. In this view, north is to the left of the picture and solar illumination is from the bottom of the frame. The image was obtained in visible light with the Cassini spacecraft narrow angle camera on Dec. 31, 2004, at a distance of about 123,400 kilometers (76,677 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 78 degrees. Resolution achieved in the original image was 740 meters (2,428 feet) per pixel. The image has been contrast-enhanced and magnified by a factor of two to aid visibility. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . For images visit the Cassini imaging team home page http://ciclops.org . Credit: NASA/JPL/Space Science Institute
Date	January 7, 2005

Empty Nest

title	Empty Nest
date	01.18.2004
description	This image mosaic taken by the panoramic camera onboard the Mars Exploration Rover Spirit shows the rover's landing site, the Columbia Memorial Station, at Gusev Crater, Mars. This spectacular view may encapsulate Spirit's entire journey, from lander to its possible final destination toward the east hills. On its way, the rover will travel 250 meters (820 feet) northeast to a large crater approximately 200 meters (660 feet) across, the ridge of which can be seen to the left of this image. To the right are the east hills, about 3 kilometers (2 miles) away from the lander. The picture was taken on the 16th martian day, or sol, of the mission (Jan. 18/19, 2004). A portion of Spirit's solar panels appear in the foreground. Data from the panoramic camera's green, blue and infrared filters were combined to create this approximate true color image. Image Credit: NASA/JPL/Cornell

Hole in One

title	Hole in One
description	The interior of a crater surrounding the Mars Exploration Rover Opportunity at Meridiani Planum on Mars can be seen in this color image from the rover's panoramic camera. This is the darkest landing site ever visited by a spacecraft on Mars. The rim of the crater is approximately 10 meters (32 feet) from the rover. The crater is estimated to be 20 meters (65 feet) in diameter. Scientists are intrigued by the abundance of rock outcrops dispersed throughout the crater, as well as the crater's soil, which appears to be a mixture of coarse gray grains and fine reddish grains. Data taken from the camera's near-infrared, green and blue filters were combined to create this approximate true color picture, taken on the first day of Opportunity's journey. The view is to the west-southwest of the rover. Image Credit: NASA/JPL/Cornell

Rover Landing Sites

title	Rover Landing Sites
description	This Mars 2001 Odyssey composite image from orbit shows Opportunity's landing site at Meridiani Planum, Spirit's landing site at Gusev Crater and other locations on Mars. Image Credit: NASA

Phobos: Cold and Colder

title	Phobos: Cold and Colder
date	08.19.1998
description	Thermal data shows the wide range of temperatures around the massive Stickney crater on Mars' moon Phobos. Image Credit: NASA

Martian Meteorite

title	Martian Meteorite
description	NASA's Mars Exploration Rover Opportunity has found an iron meteorite, the first meteorite of any type ever identified on another planet. The pitted, basketball-size object is mostly made of iron and nickel according to readings from spectrometers on the rover. Only a small fraction of the meteorites fallen on Earth are similarly metal-rich. Others are rockier. As an example, the meteorite that blasted the famous Meteor Crater in Arizona is similar in composition. "This is a huge surprise, though maybe it shouldn't have been," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science instruments on Opportunity and its twin, Spirit. The meteorite, dubbed "Heat Shield Rock," sits near debris of Opportunity's heat shield on the surface of Meridiani Planum, a cratered flatland that has been Opportunity's home since the robot landed on Mars nearly one year ago. "I never thought we would get to use our instruments on a rock from someplace other than Mars," Squyres said. "Think about where an iron meteorite comes from: a destroyed planet or planetesimal that was big enough to differentiate into a metallic core and a rocky mantle." Rover-team scientists are wondering whether some rocks that Opportunity has seen atop the ground surface are rocky meteorites. "Mars should be hit by a lot more rocky meteorites than iron meteorites," Squyres said. "We've been seeing lots of cobbles out on the plains, and this raises the possibility that some of them may in fact be meteorites. We may be investigating some of those in coming weeks. The key is not what we'll learn about meteorites -- we have lots of meteorites on Earth -- but what the meteorites can tell us about Meridiani Planum." The numbers of exposed meteorites could be an indication of whether the plain is gradually eroding away or being built up. NASA Chief Scientist Dr. Jim Garvin said, "Exploring meteorites is a vital part of NASA's scientific agenda, and discovering whether there are storehouses of them on Mars opens new research possibilities, including further incentives for robotic and then human-based sample-return missions. Mars continues to provide unexpected science 'gold,' and our rovers have proven the value of mobile exploration with this latest finding." Initial observation of Heat Shield Rock from a distance with Opportunity's miniature thermal emission spectrometer suggested a metallic composition and raised speculation last week that it was a meteorite. The rover drove close enough to use its Moessbauer and alpha particle X-ray spectrometers, confirming the meteorite identification over the weekend. Opportunity and Spirit successfully completed their primary three-month missions on Mars in April 2004. NASA has extended their missions twice because the rovers have remained in good condition to continue exploring Mars longer than anticipated. They have found geological evidence of past wet environmental conditions that might have, been hospitable to life. Opportunity has driven a total of 2.10 kilometers (1.30 miles). Minor mottling from dust has appeared in images from the rover's rear hazard-identification camera since Opportunity entered the area of its heat-shield debris, said Jim Erickson of NASA's Jet Propulsion Laboratory, Pasadena, Calif., rover project manager. The rover team plans to begin driving Opportunity south toward a circular feature called "Vostok" within about a week. Spirit has driven a total of 4.05 kilometers (2.52 miles). It has been making slow progress uphill toward a ridge on "Husband Hill" inside Gusev Crater. Image Credit: NASA

Eyeing Eagle Crater

title	Eyeing Eagle Crater
description	This image mosaic, compiled from navigation and panoramic camera images during the Mars Exploration Rover Opportunity's 33rd, 35th, and 36th sols on Mars, shows a panoramic view of the crater where the rover had been exploring since its dramatic arrival in late January 2004. The crater, now informally referred to as "Eagle Crater," is approximately 22 meters (72 feet) in diameter. Opportunity's lander is visible in the center of the image. Track marks reveal the rover's progress. The rover cameras recorded this view as Opportunity climbed close to the crater rim as part of a soil survey campaign. Image credit: NASA/JPL/Cornell

Looking Back

title	Looking Back
date	03.26.2004
description	NASA's Opportunity rover looks back at the crater where it landed and spent the first two months of its mission exploring exposed bedrock. This area may have been the shore of a shallow sea. The image is the first 360-degree view from the Mars Exploration Rover Opportunity's new position outside "Eagle Crater," the small crater where the rover landed about two months ago. Scientists are busy analyzing Opportunity's new view of the plains of Meridiani Planum. The plentiful ripples are a clear indication that wind is the primary geologic process currently in effect on the plains. The rover's tracks can be seen leading away from Eagle Crater. At the far left are two depressions - each about a meter (about 3.3 feet) across - that feature bright spots in their centers. One possibility is that the bright material is similar in composition to the rocks in Eagle Crater's outcrop and the surrounding darker material is what's referred to as "lag deposit," or erosional remnants, which are much harder and more difficult to wear away. These twin dimples might be revealing pieces of a larger outcrop that lies beneath. The depression closest to Opportunity is whimsically referred to as "Homeplate" and the one behind it as "First Base." The backshell and parachute that helped protect the rover and deliver it safely to the surface of Mars are also visible near the horizon, at the left of the image. This image was taken by the rover's navigation camera. Image Credi: NASA/JPL

A Bird's-Eye View of Erebus

title	A Bird's-Eye View of Erebus
date	11.23.2005
description	This false-color view combines frames taken by the panoramic camera on NASA's Mars Exploration Rover Opportunity on the rover's 652 through 663 Martian days, or sols (Nov. 23 to Dec. 5, 2005), at the edge of Erebus Crater. The mosaic is presented as a vertical projection. This type of projection provides a true-to-scale overhead view of the rover deck and nearby surrounding terrain. The view here shows outcrop rocks, sand dunes, and other features out to a distance of about 25 meters (82 feet) from the rover. Opportunity examined targets on the outcrop called "Rimrock" in front of the rover, testing the mobility and operation of Opportunity's robotic arm. The view shows examples of the dunes and ripples that Opportunity has been crossing as the rover drives on the Meridiani plains. Image credit: NASA/JPL-Caltech/Cornell

'McMurdo' Panorama from Spirit's 'Winter Haven'

'McMurdo' Panorama from Spir …

title	'McMurdo' Panorama from Spirit's 'Winter Haven'
description	This 360-degree view, called the "McMurdo" panorama, comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Spirit. From April through October 2006, Spirit has stayed on a small hill known as "Low Ridge." There, the rover's solar panels are tilted toward the sun to maintain enough solar power for Spirit to keep making scientific observations throughout the winter on southern Mars. This view of the surroundings from Spirit's "Winter Haven" is presented in approximately true color. Oct. 26, 2006, marks Spirit's 1,000th sol of what was planned as a 90-sol mission. (A sol is a Martian day, which lasts 24 hours, 39 minutes, 35 seconds). The rover has lived through the most challenging part of its second Martian winter. Its solar power levels are rising again. Spring in the southern hemisphere of Mars will begin in early 2007. Before that, the rover team hopes to start driving Spirit again toward scientifically interesting places in the "Inner Basin" and "Columbia Hills" inside Gusev crater. The McMurdo panorama is providing team members with key pieces of scientific and topographic information for choosing where to continue Spirit's exploration adventure. The Pancam began shooting component images of this panorama during Spirit's sol 814 (April 18, 2006) and completed the part shown here on sol 932 (Aug. 17, 2006). The panorama was acquired using all 13 of the Pancam's color filters, using lossless compression for the red and blue stereo filters, and only modest levels of compression on the remaining filters. The overall panorama consists of 1,449 Pancam images and represents a raw data volume of nearly 500 megabytes. It is thus the largest, highest-fidelity view of Mars acquired from either rover. Additional photo coverage of the parts of the rover deck not shown here was completed on sol 980 (Oct. 5 , 2006). The team is completing the processing and mosaicking of those final pieces of the panorama, and that image will be released on the Web shortly to augment this McMurdo panorama view. This beautiful scene reveals a tremendous amount of detail in Spirit's surroundings. Many dark, porous-textured volcanic rocks can be seen around the rover, including many on Low Ridge. Two rocks to the right of center, brighter and smoother-looking in this image and more reflective in infrared observations by Spirit's miniature thermal emission spectrometer, are thought to be meteorites. On the right, "Husband Hill" on the horizon, the rippled "El Dorado" sand dune field near the base of that hill, and lighter-toned "Home Plate" below the dunes provide context for Spirit's travels since mid-2005. Left of center, tracks and a trench dug by Spirit's right-front wheel, which no longer rotates, have exposed bright underlying material. This bright material is evidence of sulfur-rich salty minerals in the subsurface, which may provide clues about the watery past of this part of Gusev Crater. Spirit has stayed busy at Winter Haven during the past, six months even without driving. In addition to acquiring this spectacular panorama, the rover team has also acquired significant new assessments of the elemental chemistry and mineralogy of rocks and soil targets within reach of the rover's arm. The team plans soon to have Spirit drive to a very nearby spot on Low Ridge to access different rock and soil samples while maintaining a good solar panel tilt toward the sun for the rest of the Martian winter. Despite the long span of time needed for acquiring this 360-degree view -- a few images at a time every few sols over a total of 119 sols because the available power was so low -- the lighting and color remain remarkably uniform across the mosaic. This fact attests to the repeatability of wintertime sols on Mars in the southern hemisphere.

Getting a Sense of Scale

title	Getting a Sense of Scale
date	10.06.2006
description	This photo composite shows an aerial view of FedEx Field in Landover, Md., home of the Washington Redskins, superimposed on Mars' Victoria Crater to give a sense of the crater's scale. Image Credit: FedEx Field: Screenshot (c) Google Inc. and reproduced with permission. Victoria Crater: NASA/JPL/UA

Viking 1 on Mars

title	Viking 1 on Mars
date	07.23.1976
description	Sand dunes and large rocks are revealed in this panoramic image of Mars taken by Viking 1's Camera 1. The horizon is approximately 3 kilometers (2 miles) away. The late afternoon sun is high in the sky over the left side of the picture. The support struts of the S-band high-gain antenna extends to the top of the picture. The American flags are located on the two RTG (Radioisotope Thermoeletric Generator) wind screens. In the middle third of the picture the rocky surface is covered by thick deposits of wind-blown material, forming numerous dunes. At the center of the picture on the horizon are two low hills which may be part of the rim of the distant crater. Two very large rocks are visible in the middle ground, the nearer one is 3 meters (10 feet) in diameter and is 8 meters (25 feets) from the spacecraft. A cloud layer is visible halfway between the horizon and the top of the picture. The meterology boom is located right of center. Behind it, the "White Mesa" is visible. In the nearer ground are numerous rocks about 10cm (4 inches) across, with horse-shoe shaped scour marks on their upwind side and wind tails in their lee. The fine grained material in the front of them contains small pits formed by impact of material kicked out by the lander's descent rocket engines. Image Credit: NASA

Victoria Crater' at Meridian …

title	Victoria Crater' at Meridiani Planum
date	10.06.2006
description	This image from the High Resolution Imaging Science Experiment on NASA's Mars Reconnaissance Orbiter shows "Victoria crater," an impact crater at Meridiani Planum, near the equator of Mars. The crater is approximately 800 meters (half a mile) in diameter. It has a distinctive scalloped shape to its rim, caused by erosion and downhill movement of crater wall material. Layered sedimentary rocks are exposed along the inner wall of the crater, and boulders that have fallen from the crater wall are visible on the crater floor. The floor of the crater is occupied by a striking field of sand dunes. Since January 2004, the Mars Exploration Rover Opportunity has been operating at Meridiani Planum. Five days before this image was taken, Opportunity arrived at the rim of Victoria crater, after a drive of more than 9 kilometers (over 5 miles). The rover can be seen in this image, at roughly the "ten o'clock" position along the rim of the crater. This view is a portion of an image taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on Oct. 3, 2006. The complete image is centered at minus7.8 degrees latitude, 279.5 degrees East longitude. The range to the target site was 297 kilometers (185.6 miles). At this distance the image scale is 29.7 centimeters (12 inches) per pixel (with 1 x 1 binning) so objects about 89 centimeters (35 inches) across are resolved. The image shown here has been map-projected to 25 centimeters (10 inches) per pixel and north is up. The image was taken at a local Mars time of 3:30 PM and the scene is illuminated from the west with a solar incidence angle of 59.7 degrees, thus the sun was about 30.3 degrees above the horizon. At a solar longitude of 113.6 degrees, the season on Mars is northern summer. This is an enhanced-color view generated from images acquired by the HiRISE camera using its red filter and blue-green filter. Images from the High Resolution Imaging Science Experiment and additional information about the Mars Reconnaissance Orbiter are available online at: http://www.nasa.gov/mroor http://HiRISE.lpl.arizona.edu. For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace & Technologies Corporation and is operated by the University of Arizona. Image Credit: NASA/JPL/UA

Mars Exploration Rover "Spirit" Launches

Mars Exploration Rover "Spir …

title	Mars Exploration Rover "Spirit" Launches
date	06.10.2003
description	Amid billows of smoke and steam, the Delta II rocket with its Mars Exploration Rover (MER-A) payload lifts off the pad on time at 1:58 p.m. EDT from Launch Complex 17-A, Cape Canaveral Air Force Station. MER-A, known as "Spirit," is the first of two rovers being launched to Mars. When the two rovers arrive at the red planet in 2004, they will bounce to airbag-cushioned landings at sites offering a balance of favorable conditions for safe landings and interesting science. The rovers see sharper images, can explore farther and examine rocks better than anything that has ever landed on Mars. The designated site for the MER-A mission is Gusev Crater, which appears to have been a crater lake. The second rover, MER-B, is scheduled to launch June 25. Image Credit: NASA

Opportunity's Second Martian Birthday at Cape Verde

Opportunity's Second Martian …

title	Opportunity's Second Martian Birthday at Cape Verde
date	10.20.2007
description	A promontory nicknamed "Cape Verde" can be seen jutting out from the walls of Victoria Crater in this approximate true-color picture taken by the panoramic camera on NASA's Mars Exploration Rover Opportunity. The rover took this picture on martian day, or sol, 1329 (Oct. 20, 2007), more than a month after it began descending down the crater walls - and just 9 sols shy of its second Martian birthday on sol 1338 (Oct. 29, 2007). Opportunity landed on the Red Planet on Jan. 25, 2004. That's nearly four years ago on Earth, but only two on Mars because Mars takes longer to travel around the sun than Earth. One Martian year equals 687 Earth days. The overall soft quality of the image, and the "haze" seen in the lower right portion, are the result of scattered light from dust on the front sapphire window of the rover's camera. This view was taken using three panoramic-camera filters, admitting light with wavelengths centered at 750 nanometers (near infrared), 530 nanometers (green) and 430 nanometers (violet). Image Credit: NASA/JPL-Caltech/Cornell

Spirit's Race Against Winter

title	Spirit's Race Against Winter
date	11.29.2007
description	While struggling to reach a winter outpost necessary for survival on Mars, Spirit has been slowed by sand in the bottom of a shallow, bowl-like depression. Spirit's goal is to reach a slope on the north edge of "Home Plate" that will keep its solar panels trained on the Sun. If the rover can collect enough sunlight to survive, Spirit will continue to study terrain near "Home Plate," which the rover reached after crossing the floor of Gusev Crater and scaling the "Columbia Hills." This map shows the rover's progress from July 2004 to November 2007. Image credit: NASA/JPL-Caltech/USGS/UNM/High-Resolution Science Imaging Experiment

Gullies with Characteristics of Water-Carved Channels

Gullies with Characteristics …

title	Gullies with Characteristics of Water-Carved Channels
description	False-color image of gully channels in a crater in the southern highlands of Mars, taken by the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter. The gullies emanating from the rocky cliffs near the crater's rim (upper left) show meandering and braided patterns typical of water-carved channels. North is approximately up and illumination is from the left, scale, 26 centimeters per pixel. A link to the full HiRISE image that includes this view is online at http://hirise.lpl.arizona.edu/PSP_003583_1425 Credit: NASA/JPL/University of Arizona

CRISM Views Phobos and Deimo …

title	CRISM Views Phobos and Deimos
date	10.22.2007
description	Phobos' surface contains a second material, grayer-colored ejecta from a 9-kilometer (5.6-mile) diameter crater. This crater, called Stickney, is located at the upper left limb of Phobos and the grayer-colored ejecta extends toward the lower right. These CRISM measurements are the first spectral measurements to resolve the disk of Deimos, and the first of this part of Phobos to cover the full wavelength range needed to assess the presence of iron-, water-, and carbon-containing minerals. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad. Credit: NASA/JPL/JHUAPL, These two images taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show Mars' two small moons, Phobos and Deimos, as seen from the Mars Reconnaissance Orbiter's low orbit around Mars. Both images were taken while the spacecraft was over Mars' night side, with the spacecraft turned off its normal nadir-viewing geometry to glimpse the moons. The image of Phobos, shown at the top, was taken at 0119 UTC on October 23 (9:19 p.m. EDT on Oct. 22), and shows features as small as 400 meters (1,320 feet) across. The image of Deimos, shown at the bottom, was taken at 2016 UTC (12:16 p.m. EDT) on June 7, 2007, and shows features as small as 1.3 kilometers (0.8 miles) across. Both CRISM images were taken in 544 colors covering 0.36-3.92 micrometers, and are displayed at twice the size in the original data for viewing purposes. Phobos and Deimos are about 21 and 12 kilometers (13.0 and 7.5 miles) in diameter and orbit Mars with periods of 7 hours, 39.2 minutes and 1 day, 6 hours, 17.9 minutes respectively. Because Phobos orbits Mars in a shorter time than Mars' 24 hour, 37.4-minute rotational period, to an observer on Mars' surface it would appear to rise in the west and set in the east. From Mars' surface, Phobos appears about one-third the diameter of the Moon from Earth, whereas Deimos appears as a bright star. The moons were discovered in 1877 by the astronomer Asaph Hall, and as satellites of a planet named for the Roman god of war, they were named for Greek mythological figures that personify fear and terror. The first spacecraft measurements of Phobos and Deimos, from the Mariner 9 and Viking Orbiter spacecraft, showed that both moons have dark surfaces reflecting only 5 to 7% of the sunlight that falls on them. The first reconstruction of the moons' spectrum of reflected sunlight was a difficult compilation from three different instruments, and appeared to show a flat, grayish spectrum resembling carbonaceous chondrite meteorites. Carbonaceous chondrites are primitive carbon-containing materials thought to originate in the outer part of the asteroid belt. This led to a commonly held view among planetary scientists that Mars' moons are primitive asteroids captured into Martian orbit early in the planet's history. More recent measurements have shown that the moons are in fact relatively red in their color, and resemble even more primitive D-type asteroids in the outer solar system. Those ultra-primitive bodies are also thought to contain carbon as well as water ice, but to have experienced even less geochemical processing than many carbonaceous chondrites. The version of the CRISM images shown here were constructed by displaying 0.90, 0.70, and 0.50 micrometer wavelengths in the red, green, and blue image planes. This is a broader range of colors than is visible to the human eye, but it accentuates color differences. Both moons are shown with colors scaled in the same way. Deimos is red-colored like most of Phobos. However,

Mariner Crater on Mars

title	Mariner Crater on Mars
date	07.15.1965
description	Mariner 4 image of the crater named after it, the 151 km diameter Mariner crater at 35 S, 164 W. Running from the lower left corner of the frame through the bottom of the crater is a linear ridge which is part of Sirenum Fossae. The image was taken from 12,600 km and covers 250 km by 254 km. North is up. (Mariner 4, frame 11E) Image Credit: NASA

Columbia Memorial

title	Columbia Memorial
date	01.06.2004
description	The landing site of the Mars Spirit rover in honor of the astronauts who died in the tragic accident of the Space Shuttle Columbia in February. The area in the vast flatland of the Gusev Crater where Spirit landed this weekend will be called the Columbia Memorial Station. Since its historic landing, Spirit has been sending extraordinary images of its new surroundings on the red planet over the past few days. Among them, an image of a memorial plaque placed on the spacecraft to Columbia's astronauts and the STS-107 mission. The plaque is mounted on the back of Spirit's high-gain antenna, a disc-shaped tool used for communicating directly with Earth. The plaque is aluminum and approximately six inches in diameter. The memorial plaque was attached March 28, 2003, at the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, Fla. Chris Voorhees and Peter Illsley, Mars Exploration Rover engineers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., designed the plaque. Image Credit: NASA

Gusev Crater

title	Gusev Crater
description	On January 3, Spirit, NASA's 400-pound rover, is scheduled to land on what may be a dried-up lake bed on Mars. "There's not much doubt: this site contained a body of liquid water, at least for some amount of time," says Jim Garvin, NASA's Lead Scientist for Mars Exploration. The site is Gusev Crater, a 90-mile wide hole in the ground that probably formed three to four billion years ago when an asteroid crashed just south of Mars' equator. There's a channel system that drains into it, which probably carried liquid water, or water and ice, into the crater. "It's hard to imagine the landscape looking this way unless water was somehow involved," says Garvin. This image was taken by NASA's Viking orbiter. Right now, inside the crater, researchers expect to find sediments, which may be nearly 3,000 feet thick. These sediments, which, researchers hope were deposited by water, may have been covered by dust and sand that's blown into the crater over the past two billion years. But if there was once water in Gusev, its signature should still be there. Image Credit: NASA

Spirit Descent

title	Spirit Descent
date	01.03.2004
description	This image, taken by the descent image motion estimation system camera located on the bottom of the Mars Exploration Rover Spirit's lander, shows a view of Gusev Crater as the lander descends to Mars. The picture is taken at an altitude of 1400 meters. Numerous small impact craters can be seen on the surface of the planet. These images help the onboard software to minimize the lander's horizontal velocity before its bridal is cut, and it falls freely to the surface of Mars. See more Spirit images in the Mars Exploration Rover Image Gallery. Image Credit: NASA

Mars in 3-D

title	Mars in 3-D
description	This sprawling look at the martian landscape surrounding the Mars Exploration Rover Spirit is the first 3-D stereo image from the rover's navigation camera. A surface depression nicknamed "Sleepy Hollow" can be seen to center left of the image. Scientists theorize that this topographic feature, measuring about 10 meters (30 feet) in diameter and located approximately 10 to 20 meters (30 to 60 feet) away from Spirit, is either an impact crater or a product of wind-erosion. See more images in the Mars Exploration Rover Image Gallery. Image credit:NASA/JPL

Many Worlds, Many Craters

title	Many Worlds, Many Craters
description	A comparison of ~30-kilometer-diameter impact craters on several planetary bodies. All craters are shown at the same scale and have been rotated so that the light source is from the left. This rotation puts north at the bottom of the images of the lunar crater and the Ganymede crater. Names and locations of the four craters are as follows: Golubkhina (Venus), 60.30N, 286.40E, Kepler (Moon), 8.10N, 38.10W, (Mars), 20.80S, 53.60E, (Ganymede), 29.80S, 136.00W. Image Credit: Image of Ganymede Crater contributed by Paul Schenk (Lunar and Planetary Institute). Image of Mars crater obtained from the Mars Multi-Scale Map, Calvin Hamilton (Los Alamos National Laboratory). Images of lunar and venusian craters from Robert Herrick (Lunar and Planetary Institute).

Uranius Tholus

title	Uranius Tholus
description	This Viking orbiter image shows Uranius Tholus, one of the smaller volcanos in the Tharsis region of Mars. It is only 60 kilometers across and 3 kilometers higher than the surrounding plains. In comparison with Olympus Mons, the greater number of impact craters near Uranius Tholus implies that it is substantially older than Olympus Mons. One such crater in the top center of the image has been flooded by lava from the surrounding plains. Because this crater must have formed after the volcano but before the plains, the plains must be younger than the volcano. (This is an example of using superposition relationships to determine the relative age of a series of features by determining which features lie on top of other features.) This area is believed to be more than 3 billion years old. This image was taken by NASA's Viking 1 orbiter in 1977. Image Credit: NASA

Phobos' Stickney Crater

title	Phobos' Stickney Crater
date	08.19.1998
description	This image of Phobos, the inner and larger of the two moons of Mars, was taken by Mars Global Surveyor in 1998. This image shows a close-up of the largest crater on Phobos, Stickney, 10 kilometers in diameter. Individual boulders are visible on the near rim of the crater, and are presumed to be ejecta blocks from the impact that formed Stickney. Some of these boulders are enormous, more than 50 meters across. Also crossing at and near the rim of Stickney are shallow, elongated depressions called grooves. This crater is nearly half the size of Phobos, and these grooves may be fractures caused by its formation. Phobos was observed by both the Mars Orbiter Camera (MOC) and Thermal Emission Spectrometer (TES). This image is one of the highest-resolution images (4 meters per pixel) ever obtained of the martian satellite. Image Credit: NASA, Jet Propulsion Laboratory, Malin Space Science Systems

Ancient Martian Highlands

title	Ancient Martian Highlands
description	The meteorite ALH 84001, where possible traces of martian life have been found, is one of the oldest rocks ever studied The meteorite probably came from one of the oldest regions on Mars. These ancient parts of Mars, most of its southern hemisphere, are covered with asteroid impact craters, like this area in the bright region of Noachis. This part of Mars is as cratered as the Moon's highlands and is about the same age, more than 4 billion years old. The biggest crater here is Proctor, named for a nineteenth-century British astronomer. The dark splotches inside Proctor and many other craters are fields of sand dunes. In high-resolution images, these linear dunes look like waves on the ocean, but they actually show how dry and desolate Mars is now. This image was taken by the Viking 1 orbiter in 1977. Image Credit: NASA, Lunar and Planetary Institute

Martian Landslide

title	Martian Landslide
description	Although Valles Marineris originated as a tectonic structure, it has been modified by other processes. This image shows a close-up view of a landslide on the south wall of Valles Marineris. This landslide partially removed the rim of the crater that is on the plateau adjacent to Valles Marineris. Note the texture of the landslide deposit where it flowed across the floor of Valles Marineris. Several distinct layers can be seen in the walls of the trough. These layers may be regions of distinct chemical composition or mechanical properties in the martian crust. This image is 60 kilometers across. This image was taken by the Viking 1 orbiter in 1977. Image Credit: NASA

Asteroid Ida and its Satellite Dactyl in Enhanced Color

Asteroid Ida and its Satelli …

title	Asteroid Ida and its Satellite Dactyl in Enhanced Color
date	08.28.1993
description	During its examination of the asteroid Ida, the Galileo spacecraft returned images of a second object, Dactyl--the first confirmed satellite or moon of an asteroid, the much smaller moon is visible to the right of Ida. Asteroids are small interplanetary bodies of rock or metal that mostly orbit the Sun in a belt between Mars and Jupiter, but others are known elsewhere in the solar system. The Galileo spacecraft surveyed Ida in 1993 on its way to explore the Jupiter system in 1995-97. This color picture was made from images taken by the imaging system on the Galileo spacecraft about 14 minutes before its closest approach to asteroid 243 Ida on August 28, 1993. The range from the spacecraft was about 10,500 kilometers (6,500 miles). The images used are from the sequence in which Ida's moon 1993(2433)1 Dactyl was discovered. This picture contains images through the 4100-angstrom (violet), 7560 A (infrared) and 9680 A (infrared) filters. The color is "enhanced" in the sense that the CCD camera is sensitive to near infrared wavelengths of light beyond human vision, a "natural" color picture of this asteroid would appear mostly gray. Shadings in the image indicate changes in illumination angle on the many steep slopes of this irregular body as well as subtle color variations due to differences in the physical state and composition of the soil (regolith). There are brighter areas, appearing bluish in the picture, around craters on the upper left end of Ida, around the small bright crater near the center of the asteroid, and near the upper right-hand edge (the limb). This combination of more reflected blue light and greater absorption of near infrared light, suggest a difference in the abundance or composition of iron-bearing minerals in these areas. Ida's moon also has a deeper near-infrared absorption and a different color in the violet than any area on this side of Ida. The moon is not identical in spectral properties to any area of Ida in view here, though its overall similarity in reflectance and general spectral type suggests that it is made of the same basic rock types. Resolved images of Ida over a full rotation period (4.633 h) allowed detailed shape models to be developed, yielding volumes of 16,000+ -1,900 km cubed for Ida (mean radius, 15.7 km) and 1.4 km cubed for Dactyl (mean radius, 0.7 km, Belton et al., 1995, Nature, v. 374, p. 785- 788). These images and other data collected by the Galileo spacecraft may allow scientists to determine whether these asteroids are pieces of bigger ones that at one time partly melted and differentiated (forming a dense metallic core and rocky crust) or whether these are pieces of material unaltered since their formation during the birth of the Solar System. Image Credit: NASA

High-Resolution MOC Image of …

title	High-Resolution MOC Image of Phobos
date	08.19.1998
description	This image of Phobos, the inner and larger of the two moons of Mars, was taken by the Mars Global Surveyor on August 19, 1998. This image shows a close-up of the largest crater on Phobos, Stickney, 10 kilometers (6 miles) in diameter. Individual boulders are visible on the near rim of the crater, and are presumed to be ejecta blocks from the impact that formed Stickney. Some of these boulders are enormous - more than 50 meters (160 feet) across. Also crossing at and near the rim of Stickney are shallow, elongated depressions called grooves. This crater is nearly half the size of Phobos and these grooves may be fractures caused by its formation. Phobos was observed by both the Mars Orbiter Camera (MOC) and Thermal Emission Spectrometer (TES). This image is one of the highest resolution images (4 meters or 13 feet per picture element or pixel) ever obtained of the Martian satellite. Malin Space Science Systems, Inc. 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 Thermal Emission Spectrometer is operated by Arizona State University and was built by Raytheon Santa Barbara Remote Sensing. 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. Image Credit: Erich Karkoschka (University of Arizona Lunar & Planetary Lab) and NASA

Peeking Out

title	Peeking Out
description	From its new location at the inner edge of the small crater surrounding it, the Mars Exploration Rover Opportunity was able to look out to the plains where its backshell (left) and parachute (right) landed. This approximate true-color image was created by combining data from the panoramic camera's red, green and blue filters. Image credit: NASA/JPL/Cornell

Spirit Launch

title	Spirit Launch
date	06.10.2003
description	A trail of smoke is all that identifies the Delta II rocket with the Mars Exploration Rover Spirit aboard as it hurtles into space. Liftoff occurred on time at 1:58 p.m. EDT from Launch Complex 17-A, Cape Canaveral Air Force Station. Spirit was the first of two rovers launched to Mars in the summer of 2003. Spirit and its twin, Opportunity, landed on opposite sides of the planet in January 2004. The rovers see sharper images, can explore farther and examine rocks better than anything that has ever landed on Mars. Spirit's destination was Gusev Crater, which appears to have been a crater lake. Image Credit: NASA

Gaspra - Highest Resolution …

title	Gaspra - Highest Resolution Mosaic
date	10.29.1991
description	This picture of asteroid 951 Gaspra is a mosaic of two images taken by the Galileo spacecraft from a range of 5,300 kilometers (3,300 miles), some 10 minutes before closest approach on October 29, 1991. The Sun is shining from the right, phase angle is 50 degrees. The resolution, about 54 meters/pixel, is the highest for the Gaspra encounter and is about three times better than that in the view released in November 1991. Gaspra is an irregular body with dimensions about 19 x 12 x 11 kilometers (12 x 7.5 x 7 miles). The portion illuminated in this view is about 18 kilometers (11 miles) from lower left to upper right. The north pole is located at upper left, Gaspra rotates counterclockwise every 7 hours. The large concavity on the lower right limb is about 6 kilometers (3.7 miles) across, the prominent crater on the terminator, center left, about 1.5 kilometers (1 mile). A striking feature of Gaspra's surface is the abundance of small craters. More than 600 craters, 100-500 meters (330-1650 feet) in diameter are visible here. The number of such small craters compared to larger ones is much greater for Gaspra than for previously studied bodies of comparable size such as the satellites of Mars. Gaspra's very irregular shape suggests that the asteroid was derived from a larger body by nearly catastrophic collisions. Consistent with such a history is the prominence of groove-like linear features, believed to be related to fractures. These linear depressions, 100-300 meters wide and tens of meters deep, are in two crossing groups with slightly different morphology, one group wider and more pitted than the other. Grooves had previously been seen only on Mars's moon Phobos, but were predicted for asteroids as well. Gaspra also shows a variety of enigmatic curved depressions and ridges in the terminator region at left. The Galileo project, whose primary mission is the exploration of the Jupiter system in 1995-97, is managed for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory. Image Credit: JPL

'Happy Face' Crater

title	'Happy Face' Crater
date	03.10.1999
description	Mars Global Surveyor was greeted with this view of 'Happy Face Crater' smiling back at its camera from its location on the east side of Argyre Planitia. This crater is officially known as Galle Crater, and it is about 215 kilometers (134 miles) across. The picture was taken by the MOC's red and blue wide angle cameras. The bluish-white tone is caused by wintertime frost. Illumination is from the upper left. For more information and Viking Orbiter views of "Happy Face Crater," see http://www.msss.com/education/happy_face/happy_face.html. Image Credit: NASA

Endurance Crater

title	Endurance Crater
description	This navigation camera mosaic, created from images taken by NASA's Mars Exploration Rover Opportunity on sols 115 and 116 (May 21 and 22, 2004) provides a dramatic view of "Endurance Crater." The rover engineering team carefully plotted the safest path into the football field-sized crater, eventually easing the rover down the slopes around sol 130 (June 12, 2004). To the upper left of the crater sits the rover's protective heatshield, which sheltered Opportunity as it passed through the martian atmosphere. The 360-degree view is presented in a cylindrical projection, with geometric and radiometric seam correction. Image Credit: NASA/JPL

Mars River Delta?

title	Mars River Delta?
description	A high-resolution TIFF file of this image is available at http://photojournal.jpl.nasa.gov/catalog/PIA04869. Details in a fan-shaped deposit discovered by NASA's Mars Global Surveyor orbiter provide evidence that some ancient rivers on Mars flowed for a long time, not just in brief, intense floods. The apron of debris filling the middle of this picture from the spacecraft's Mars Orbiter Camera is a hardened and eroded distributory fan, a type of geological feature that includes river deltas and alluvial fans. Sediments transported through valleys by water on early Mars formed the 13-kilometer-long (8-mile) deposit in the distant past, when it was still possible for liquid water to flow across the martian surface. Mars Orbiter Camera team members published discovery of this feature in the online edition of the journal Science. What is important about it? First, it provides unequivocal evidence that some valleys on Mars experienced persistent flow over considerable periods of time, as rivers do on Earth. Second, because the fan is today a deposit of sedimentary rock, it demonstrates that some sedimentary rocks on Mars were deposited in a liquid environment. Third, the fan's general shape, the pattern of its channels, and its low slopes provide circumstantial evidence that the feature was an actual delta -- that is, a deposit made when a river or stream enters a body of water. If so, this landform is a strong indicator that some craters and basins on Mars once held lakes. Hundreds of other locations on Mars where valleys enter craters and basins have been imaged by the Mars Orbiter Camera, but none has shown landforms like those presented here. The picture is a mosaic of images acquired between August 2000 and September 2003. The area covered 14 kilometer (8.7 miles) by 19.3 kilometers (12 miles). North is up. Sunlight illuminates the scene from the left. The spacecraft's narrow-angle camera takes grayscale images, the color added is based on information from a camera on Mars Odyssey. The fan is in an unnamed crater that is 64 kilometers (40 miles) in diameter, at 24.3 degrees south latitude, 33.5 degrees west longitude. The crater lies northeast of a larger one named Holden Crater. The fan is a fossil landform. That is, it is an eroded remnant of a somewhat larger and thicker deposit. The originally loose sediment was turned to rock and then eroded over time to present the features seen today. The channels through which sediment was transported are no longer present. Instead, only their floors remain, and these have been elevated by erosion so that former channels now stand as ridges. The floors of former channels became inverted in this way because they were more resistant to the forces of erosion, indicating they either were more strongly cemented than surrounding materials, or they have more coarse grains (which are harder to remove), or both. Image Credit: NASA/JPL/Malin Space Science Systems

New Gullies on Martian Sand …

title	New Gullies on Martian Sand Dune
description	As part of extended-mission science investigation using the Mars Orbiter Camera on NASA's Mars Global Surveyor spacecraft, the camera team is re-imaging many locations where previous observations revealed gullies. The intent is to see if gully-forming processes are operating on Mars at the present time. The team has found one location where a new gully formed on a dune in an unnamed crater in the Hellespontus region of Mars, west of the Hellas Basin. This pair of narrow-angle images from the Mars Orbiter Camera shows the dune as it appeared on July 17, 2002, (left) and as it appeared on April 27, 2005, (right). The nearly three Earth years of intervening time amount to about 1.4 Mars years. During this period, a couple of gullies formed on the dune slip face. It is critical to recognize that the 2002 image was obtained at a time of year when the incident sunlight was coming in from a lower angle, relative to the horizon, than in the 2005 image. If the gullies had been present in 2002, their appearance would be sharper and more pronounced than they are in the 2005 image. The gullies simply did not exist on July 17, 2002. The steep walls of the gully alcove and channels suggests that the sand in this dune is somewhat cohesive, an observation common among martian sand dunes seen by the Mars Orbiter Camera over the past eight years. Image Credit: NASA/JPL/MSSS

Evidence of Martian Quakes

title	Evidence of Martian Quakes
description	One of the many mysteries associated with martian geology is the origin of gullies found at latitudes poleward of 30 degrees latitude. Most of these gullies are found within craters or other depressions, and appear to be related to the bedrock. Several hypotheses have been proposed for their origin, including groundwater seepage and melting at the base of a dust-mantled snow pack. Some middle-latitude gullies are found on sand dunes. These gullies appear to be different from those found on the slopes of craters, but generally have been interpreted to form by similar processes. In the present martian environment, it is difficult to introduce water to the surface. The temperature and atmospheric pressure may permit water to exist, but the rate of heating of the ground and atmosphere, and the amount of energy available to warm the ground or melt snow, are not conducive to such processes. An alternative process of gully formation on these sand dunes involves frozen carbon dioxide trapped in the winter by windblown sand, then subliming rapidly enough for the escaping carbon-dioxide gas to make the sand flow as a gully-cutting fluid. As part of extended-mission science investigation using the Mars Orbiter Camera on NASA's Mars Global Surveyor spacecraft, the camera team is re-imaging many locations where previous observations revealed gullies. The intent is to see if gully-forming processes are operating on Mars at the present time. The team has found one location where a new gully formed on a dune in an unnamed crater in the Hellespontus region of Mars, west of the Hellas Basin. This pair of narrow-angle images from the Mars Orbiter Camera shows the dune as it appeared on July 17, 2002, (left) and as it appeared on April 27, 2005, (right). The nearly three Earth years of intervening time amount to about 1.4 Mars years. During this period, a couple of gullies formed on the dune slip face. It is critical to recognize that the 2002 image was obtained at a time of year when the incident sunlight was coming in from a lower angle, relative to the horizon, than in the 2005 image. If the gullies had been present in 2002, their appearance would be sharper and more pronounced than they are in the 2005 image. The gullies simply did not exist on July 17, 2002. The steep walls of the gully alcove and channels suggests that the sand in this dune is somewhat cohesive, an observation common among martian sand dunes seen by the Mars Orbiter Camera over the past eight years. Wider context for the dune is shown in a mosaic of two images from the Thermal Emission Imaging System on NASA's Mars Odyssey orbiter, encompassing the dark-toned sand dune field on the floor of a crater located near 49.8 degrees south latitude, 325.4 degrees west longitude. In this image, north is approximately up and sunlight illuminates the scene from the upper left. More information about this image can be found at: http://photojournal.jpl.nasa.gov/catalog/PIA04290

Gullies in Sirenum Terra, Ma …

title	Gullies in Sirenum Terra, Mars
date	10.03.2006
description	This enhanced-color view shows gullies in an unnamed crater in the Terra Sirenum region of Mars. It is a sub-image from a larger view imaged by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter on Oct. 3, 2006. This scene is about 254 meters (about 830 feet) wide. The upper and left regions of this scene are in shadow, yet color variations are still apparent. The high signal to noise ratio of the HiRISE camera allows for colors to be distinguished in shadows. This allows dark features to be identified as true albedo features versus topographical features. Image credit: NASA/JPL/Univ. of Arizona

Above Spirit

title	Above Spirit
date	01.03.2004
description	A mosaic image taken by Spirit's navigation camera shows the Mars Exploration Rover sitting on its landing platform only hours after touching down on Gusev Crater. The image has been reprocessed to imove the view. See more Spirit images in the Mars Exploration Rover Image Gallery. Image Credit: NASA

Rampart Crater

title	Rampart Crater
description	The ejecta deposits around Mars' impact crater Yuty (18 kilometers in diameter) consist of many overlapping lobes. Craters with this type of ejecta deposit are known as rampart craters. This type of ejecta morphology is characteristic of many craters at equatorial and midlatitudes on Mars, but is unlike that seen around small craters on the Moon. This style of ejecta deposit is believed to form when an impacting object rapidly melts ice in the subsurface. The presence of liquid water in the ejected material allows it to flow along the surface, giving the ejecta blanket its characteristic, fluidized appearance. This image was taken in 1977 by the Viking 1 orbiter. Image Credit: NASA

Asteroid Gaspra

title	Asteroid Gaspra
date	10.29.1991
description	This picture of asteroid 951 Gaspra is a mosaic of two images taken by the Galileo spacecraft from a range of 5300 kilometers, some 10 minutes before closest approach on October 29, 1991. The Sun is shining from the right, phase angle is 500. The resolution, about 54 meters/pixel, is the highest for the Gaspra encounter and is about three times better than that in the view released in November 1991. Gaspra is an irregular body with dimensions about 19 x 12 x 11 kilometers. The portion illuminated in this view is about 18 kilometers from lower left to upper right. The north pole is located at upper left, Gaspra rotates counterclockwise every 7 hours. The large concavity on the lower right limb is about 6 kilometers across. The prominent crater on the terminator, center left, is about 1.5 kilometers. A striking feature of Gaspra's surface is the abundance of small craters. More than 600 craters, 100 to 500 meters in diameter, are visible here. The number of such small craters compared to larger ones is much greater for Gaspra than for previously studied bodies of comparable size (such as the satellites of Mars). Gaspra's very irregular shape suggests that the asteroid was derived from a larger body by nearly catastrophic collisions. Consistent with such a history is the prominence of groove-like linear features believed to be related to fractures. These linear depressions, 100 to 300 meters wide and tens of meters deep, are in two crossing groups with slightly different morphology, with one group wider and more pitted than the other. Grooves had previously been seen only on Mars' moon Phobos, but were predicted for asteroids as well. Gaspra also shows a variety of enigmatic curved depressions and ridges in the terminator region at left. The Galileo project, whose primary mission was the exploration of the Jupiter system, was managed for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory. Image Credit: U.S. Geological Survey

Mars and Syrtis Major

Title	Mars and Syrtis Major
Full Description	Taking advantage of Mars's closest approach to Earth in eight years, astronomers using NASA's Hubble Space Telescope have taken the space- based observatory's sharpest views yet of the Red Planet. The telescope's Wide Field and Planetary Camera 2 snapped these images between April 27 and May 6, when Mars was 54 million miles (87 million kilometers) from Earth. From this distance the telescope could see Martian features as small as 12 miles (19 kilometers) wide. The telescope obtained four images, which, together, show the entire planet. Each view depicts the planet as it completes one quarter of its daily rotation. In these views the north polar cap is tilted toward the Earth and is visible prominently at the top of each picture. The images were taken in the middle of the Martian northern summer, when the polar cap had shrunk to its smallest size. During this season the Sun shines continuously on the polar cap. Previous telescopic and spacecraft observations have shown that this summertime "residual" polar cap is composed of water ice, just like Earth's polar caps. These Hubble telescope snapshots reveal that substantial changes in the bright and dark markings on Mars have occurred in the 20 years since the NASA Viking spacecraft missions first mapped the planet. The Martian surface is dynamic and ever changing. Some regions that were dark 20 years ago are now bright red, some areas that were bright red are now dark. Winds move sand and dust from region to region, often in spectacular dust storms. Over long timescales many of the larger bright and dark markings remain stable, but smaller details come and go as they are covered and then uncovered by sand and dust. The dark feature known as Syrtis Major was first seen telescopically by the astronomer Christiaan Huygens in the 17th century. Many small, dark, circular impact craters can be seen in this region, attesting to the Hubble telescope's ability to reveal fine detail on the planet's surface. To the south of Syrtis is a large circular feature called Hellas. Viking and more recently Mars Global Surveyor have revealed that Hellas is a large and deep impact crater. These Hubble telescope pictures show it to be filled with surface frost and water ice clouds. Along the right limb, late afternoon clouds have formed around the volcano Elysium.
Date	06/30/1999
NASA Center	Hubble Space Telescope Center

Evidence for Recent Liquid Water on Mars

Evidence for Recent Liquid W …

Title	Evidence for Recent Liquid Water on Mars
Full Description	Newton Crater is a large basin formed by an asteroid impact that probably occurred more than 3 billion years ago. It is approximately 287 kilometers (178 miles) across. The picture shown here (top) highlights the north wall of a specific, smaller crater located in the southwestern quarter of Newton Crater (above). The crater of interest was also formed by an impact, it is about 7 km (4.4 mi) across, which is about 7 times bigger than the famous Meteor Crater in northern Arizona in North America. The north wall of the small crater has many narrow gullies eroded into it. These are hypothesized to have been formed by flowing water and debris flows. Debris transported with the water created lobed and finger-like deposits at the base of the crater wall where it intersects the floor (bottom center top image). Many of the finger-like deposits have small channels indicating that a liquid, most likely water, flowed in these areas. Hundreds of individual water and debris flow events might have occurred to create the scene shown here. Each outburst of water from higher up on the crater slopes would have constituted a competition between evaporation, freezing, and gravity. The individual deposits at the ends of channels in this MOC image mosaic were used to get a rough estimate of the minimum amount of water that might be involved in each flow event. This is done first by assuming that the deposits are like debris flows on Earth. In a debris flow, no less than about 10% (and no more than 30%) of their volume is water. Second, the volume of an apron deposit is estimated by measuring the area covered in the MOC image and multiplying it by a conservative estimate of thickness, 2 meters (6.5 feet). For a flow containing only 10% water, these estimates conservatively suggest that about 2.5 million liters (660,000 gallons) of water are involved in each event, this is enough to fill about 7 community-sized swimming pools or enough to supply 20 people with their water needs for a year. The Mars Orbiter Camera (MOC) high resolution view is located near 41.1S, 159.8W and is a mosaic of three different pictures acquired between January and May 2000. The MOC scene is illuminated from the left, north is up.
Date	06/22/2000
NASA Center	Jet Propulsion Laboratory

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