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Earth and Moon of Goddard Space Flight Center (GSFC) and Jupiter
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Lunar Beauty Shot
| Title |
Lunar Beauty Shot |
| Abstract |
This is a beauty shot animation flying over the surface of the moon created in support of a series of live interviews about the 2004 lunar eclipse. Scales are not accurate in this visualization. The Earth is about 3 times larger than it would actually appear. The source of the moon texture is unknown, it is thought to be a composite from several missions. The Earth texture was captured as the Galileo spacecraft swung by the Earth in 1990 for a gravity assist on its way to Jupiter. |
| Completed |
2004-11-01 |
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Super-Earths May Circle Othe
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| Title |
Super-Earths May Circle Other Stars |
| Explanation |
Are "super-Earths" common around other star systems? Quite possibly. Unexpected evidence [ http://www.cfa.harvard.edu/press/pr0614.html ] for this came to light recently when a planet orbiting a distant star gravitationally magnified [ http://astron.berkeley.edu/~jcohn/lens.html ] the light of an even more distant star. Assuming the planet's parent star is normal red dwarf [ http://en.wikipedia.org/wiki/Red_dwarf ], the brightening is best explained if the planet is about 13 times the mass of the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap030324.html ] and orbiting at the distance of the asteroid belt [ http://antwrp.gsfc.nasa.gov/apod/ap060319.html ] in our own Solar System [ http://space.jpl.nasa.gov/ ]. Given the small number of objects observed and similar determinations already obtained for other star systems, these super-Earths might be relatively common. Astronomers speculate [ http://arxiv.org/PS_cache/astro-ph/pdf/0603/0603276.pdf ] that the planet might have grown into a Jupiter-sized [ http://antwrp.gsfc.nasa.gov/apod/ap050911.html ] planet if its star system had more gas. Since the planet was not observed directly, significant uncertainty [ http://www.aip.org/history/heisenberg/p08c.htm ] remains in its defining attributes, and future research will be aimed at better understanding this intriguing system. The above drawing [ http://www.cfa.harvard.edu/press/pr0614image.html ] gives an artist's depiction of what a super-Earth orbiting a distant red dwarf [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.html ] star might look like, complete with a hypothetical moon [ http://antwrp.gsfc.nasa.gov/apod/ap050805.html ]. |
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Stereo Saturn
| Title |
Stereo Saturn |
| Explanation |
Get out your red/blue glasses [ http://img.arc.nasa.gov/archive/desert96/redblue.html ] and launch [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] yourself into this stereo [ http://cass.jsc.nasa.gov/research/stereo_atlas/SS3D.HTM ] picture of Saturn! The picture is actually composed from two images recorded weeks apart by the Voyager 2 spacecraft [ http://vraptor.jpl.nasa.gov/voyager/voyager_fs.html ] during its visit to [ http://nssdc.gsfc.nasa.gov/planetary/voyager.html ] the Saturnian System in August of 1981. Traveling at about 35,000 miles per hour, the spacecraft's changing viewpoint from one image to the next produced this exaggerated but pleasing stereo effect [ http://antwrp.gsfc.nasa.gov/apod/ap970404.html ]. Saturn is the second largest planet [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/saturn.html ] in the Solar System, after Jupiter. Its spectacular ring system [ http://ringmaster.arc.nasa.gov/saturn/saturn.html ] is so wide that it would span the space between the Earth and Moon. Although they look solid here, Saturn's [ http://antwrp.gsfc.nasa.gov/apod/ap000129.html ] rings consist of individually orbiting bits of ice and rock ranging in size from grains of sand to barn-sized boulders. |
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Southwest Mercury
| Title |
Southwest Mercury |
| Explanation |
The planet Mercury resembles a moon. Mercury [ http://www.seds.org/nineplanets/nineplanets/mercury.html ]'s old surface is heavily cratered [ http://liftoff.msfc.nasa.gov/Academy/SPACE/SolarSystem/Meteors/Craters.html ] like many moons. Mercury [ http://www.solarviews.com/eng/mercury.htm ] is larger than most moons but smaller than Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap990806.html ]'s moon Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap990304.html ] and Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap960717.html ]'s moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap990207.html ]. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990131.html ] is the only planet more dense. A visitor to Mercury's surface [ http://antwrp.gsfc.nasa.gov/apod/ap960121.html ] would see some strange sights. Because Mercury [ http://www.oulu.fi/~spaceweb/textbook/mercury.html ] rotates exactly three times every two orbits around the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ], and because Mercury [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mercury.html ]'s orbit is so elliptical, a visitor to Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap990102.html ] might see the Sun [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/interv.html ] rise, stop in the sky, go back toward the rising horizon [ http://antwrp.gsfc.nasa.gov/apod/ap990619.html ], stop again, and then set quickly over the other horizon. From Earth [ http://antwrp.gsfc.nasa.gov/apod/ap980530.html ], Mercury's proximity to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ] cause it to be visible only for a short time just after sunset or just before sunrise. |
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Sky and Planets
| Title |
Sky and Planets |
| Explanation |
On February 10th, an evocative [ http://www.jps.net/ssumner/ ] evening sky above Rocklin, California, USA inspired astrophotographer Steve Sumner to record this remarkable sight - five planets and the Moon. Near its first quarter phase, the bright Moon [ http://lunar.arc.nasa.gov/ ] was intentionally overexposed but Saturn [ http://www.jpl.nasa.gov/cassini/ ], Jupiter [ http://galileo.jpl.nasa.gov/ ], Mars [ http://mars.jpl.nasa.gov/ ], and Mercury [ http://sd-www.jhuapl.edu/MESSENGER/ ] (and, of course, planet Earth's [ http://www.earth.nasa.gov/ ] horizon) are all clearly visible in the deepening twilight. Notably absent in this grouping of naked-eye planets is Venus [ http://antwrp.gsfc.nasa.gov/apod/ap990903.html ] which is still putting in an early appearance as the morning star [ http://ispec.scibernet.com/station/morn_star.html ]. This month, Mercury has joined Venus in the dawn twilight while Saturn, Jupiter, and Mars still shine brightly in the western sky at nightfall [ http://www.skypub.com/sights/sights.shtml ] making another gorgeous close grouping with the crescent Moon [ http://www.inconstantmoon.com/ ]. |
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Venus, Moon, and Neighbors
| Title |
Venus, Moon, and Neighbors |
| Explanation |
Rising before the Sun on February 2nd, astrophotographer [ http://pages.prodigy.net/pam.orman/JoeGallery.html ] Joe Orman anticipated [ http://pages.prodigy.net/pam.orman/JoeAlmanac2000.html ] this apparition of the bright morning star [ http://ispec.scibernet.com/station/morn_star.html ] Venus near a lovely crescent Moon above a neighbor's house in suburban Phoenix, Arizona, USA. Fortunately, the alignment of bright planets and the Moon is one of the most inspiring sights in the night sky [ http://www.skypub.com/sights/skyevents/0004skyevents.html ] and one that is often easy to enjoy and share without any special equipment. Take tonight [ http://spacescience.com/headlines/y2000/ast30mar_1m.htm ], for example. Those blessed with clear skies can simply step outside near sunset and view a young crescent Moon very near three bright planets in the west Jupiter [ http://galileo.jpl.nasa.gov/ ], Mars [ http://mars.jpl.nasa.gov/mgs/ ], and Saturn [ http://www.jpl.nasa.gov/cassini/ ]. Jupiter will be the unmistakable brightest star near the Moon with a reddish Mars just to Jupiter's north and pale yellow Saturn directly above. Of course, these sky shows [ http://drumright.ossm.edu/astronomy/conjunctions.html ] create an evocative picture [ http://antwrp.gsfc.nasa.gov/apod/ap000310.html ] but the planets and Moon just appear to be near each other -- they are actually only approximately lined up and lie in widely separated orbits. Unfortunately, next month's highly publicized alignment of planets [ http://www.griffithobs.org/SkyAlignments.html ] on May 5th will be lost from view in the Sun's glare but such planetary alignments [ http://www.skypub.com/news/special/whypanic.html ] occur repeatedly and pose no danger [ http://www.badastronomy.com/bad/misc/planets.html ] to planet Earth. |
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Planets In The Sun
| Title |
Planets In The Sun |
| Explanation |
Today [ http://science.nasa.gov/headlines/y2000/ast02may_1.htm ], all five naked-eye planets [ http://www.seds.org/nineplanets/nineplanets/ ] (Mercury, Venus, Mars, Jupiter, Saturn) plus the Moon and the Sun [ http://helios.gsfc.nasa.gov/ sun.html ] will at least approximately line-up. As viewed [ http://drumright.ossm.edu/astronomy/conjunctions.html ] from planet Earth, they will be clustered within about 26 degrees, the closest alignment for all these celestial bodies [ http://science.nasa.gov/headlines/y2000/ ast30mar_1m.htm#alignments ] since February 1962, when there was a solar eclipse [ http://antwrp.gsfc.nasa.gov/apod/ap990818.html ]! Such planetary alignments [ http://www.griffithobs.org/SkyAlignments.html ] are not dangerous, except of course that the Sun might hurt your eyes when you look at it [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ]. So it might be easier [ http://sohowww.nascom.nasa.gov/hotshots/ ] to appreciate today's solar system [ http://space.jpl.nasa.gov/ ] spectacle if |
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A Continuous Eruption on Jup
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| Title |
A Continuous Eruption on Jupiter's Moon Io |
| Explanation |
A volcano on Jupiter's moon Io [ http://www.seds.org/nineplanets/nineplanets/io.html ] has been photographed recently during an ongoing eruption. Hot glowing lava is visible on the left on this representative-color image [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02550 ]. A glowing landscape of plateaus and valleys covered in sulfur [ http://pearl1.lanl.gov/periodic/elements/16.html ] and silicate rock [ http://windows.ivv.nasa.gov/cgi-bin/tour_def/glossary/silicate_rock.html ] surrounds the active volcano [ http://volcano.und.nodak.edu/vwdocs/planet_volcano/Io/Overview.html ]. Many features including several of the dark spots [ http://antwrp.gsfc.nasa.gov/apod/ap971110.html ] have evolved between February 2000, when the robot spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/spacecraft.html ] currently orbiting Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] took this picture, and November 1999. Io [ http://cass.jsc.nasa.gov/pub/research/outerp/io.html ] is slightly larger than Earth's Moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ] and is the closest large moon to Jupiter [ http://galileo.jpl.nasa.gov/jupiter/jupiter.html ]. The above image [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02550 ] shows a region about 250 kilometers across. How the internal structure of Io [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1990Icar...85..309R ] creates these active volcanoes [ http://antwrp.gsfc.nasa.gov/apod/ap961027.html ] remains under investigation. |
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Crater On Ice
| Title |
Crater On Ice |
| Explanation |
Impact craters are common on Earth's moon [ http://antwrp.gsfc.nasa.gov/apod/ap990326.html ] but on Jupiter's large ice moon Europa [ http://sse.jpl.nasa.gov/features/planets/jupiter/ europa.html ], they are very rare. Over time, both bodies have been subjected to an intense pounding [ http://antwrp.gsfc.nasa.gov/apod/ap990610.html ] by the solar system's formative debris [ http://www.jhuapl.edu/public/pr/000530.htm ], but geological activity on Europa's surface seems to have erased most of these impact scars. This false-color infrared image [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02561 ] from the Galileo spacecraft's NIMS instrument [ http://jumpy.igpp.ucla.edu/~nims/ ] shows a newly discovered crater on Europa as a light red ring feature near center surrounding a dark core. For scale, the dark core is about 29 kilometers in diameter. Only seven comparably [ http://antwrp.gsfc.nasa.gov/apod/ap970417.html ] large craters have now been identified on Europa's surface. Red colors in the image represent a relatively pure water ice [ http://www.glacier.rice.edu/invitation/1_icetypes.html ] composition while blue colors indicate that other minerals are present. The crater's central dark area may contain the remnants of the impacting body. The icy crust of Europa [ http://galileo.jpl.nasa.gov/moons/europa.html ] is of great interest, as evidence mounts [ http://galileo.jpl.nasa.gov/news/release/ press000110.html ] that it covers an ocean of liquid water, possibly providing suitable conditions for life. |
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Other Worlds and HD 38529
| Title |
Other Worlds and HD 38529 |
| Explanation |
After the latest round of discovery announcements [ http://www.iau.org/ga24press/ ], the list of known worlds of distant suns [ http://www.spaceart.org/lcook/extrasol.html ] has grown to 50 [ http://www.spaceref.com/news/viewnews.html?id=200 ]. While extrasolar planet [ http://exoplanets.org/ ] discoveries are [ http://obswww.unige.ch/~udry/planet/planet.html ] sure to continue, none - so far [ http://sim.jpl.nasa.gov/ ] - points clearly to another planetary system like our own [ http://antwrp.gsfc.nasa.gov/apod/ap991229.html ]. Take, for example, the newly discovered parent [ http://antwrp.gsfc.nasa.gov/apod/ap990611.html ] star HD38529 [ http://www.obspm.fr/encycl/HD38529.html ]. Shining in Earth's night sky at 6th magnitude, this sun-like star lies 137 light-years away in the constellation Orion [ http://aibn47.astro.uni-bonn.de/~gallery/constellations/orion/ main.html ]. Like most of the known extrasolar planets [ http://www.obspm.fr/encycl/encycl.html ], HD38529's planet was discovered by detecting the telltale Doppler wobble [ http://exoplanets.org/doppler.html ] in the parent star's spectrum. The data reveal that this planet orbits once every 14.3 days at an average of only 0.13 times the Earth-Sun distance and has a minimum of 0.77 Jupiter masses (about 240 Earth masses). There is even evidence [ http://www.iau.org/ga24press/pr000807_3.html#1 ] in the wobble data that HD38529, and other stars with one known planet have additional massive planets orbiting them. In this dramatic artist's vision, HD38529 and its newfound world are viewed from the moon of another massive ringed planet [ http://antwrp.gsfc.nasa.gov/apod/ap000330.html ] orbiting farther out. The ringed planet's moon is imagined to have a thin atmosphere and a surface covered with icy sheets and ridges similar to those found on Jupiter's moon Europa [ http://galileo.jpl.nasa.gov/moons/europa.html ]. |
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Folding Europa
| Title |
Folding Europa |
| Explanation |
Astypalaea Linea [ http://wwwflag.wr.usgs.gov/USGSFlag/Space/nomen/jupiter/ euroTOC.html ] on Jovian [ http://cfa-www.harvard.edu/iau/pressinfo/S1999J1.html ] ice moon Europa [ http://www.seds.org/nineplanets/nineplanets/ europa.html ] is the broad smooth region running through these images [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02960 ] recorded by the Galileo spacecraft in 1998. The pictures are different computer processed versions of the same mosaic -- on the left, small scale details have been enhanced while on the right, large scale features are emphasized. In both versions, the bold criss-crossing ridges [ http://antwrp.gsfc.nasa.gov/apod/ap981215.html ] believed to result from the upwelling of new material through cracks in the surface ice are apparent. But more easily seen on the right are recently recognized [ http://www.jhuapl.edu/public/pr/000810.htm ] gentle rises and dips, about 15 kilometers across, which likely formed as the icy surface was compressed by the addition of the new material. Further evidence [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=2000LPI....31.1182P&db_key=AST&high=3899d8d98211881 ] that stress is folding Europa's [ http://galileo.jpl.nasa.gov/moons/europa.html ] surface is offered by the presence of smaller cracks and wrinkles more easily seen on the left. These span the width of the broad swells suggestive of anticlines and synclines [ http://www.educ.uvic.ca/Faculty/jtinney/earth%20science/ ESMain.html#fold ] familiar to geologists on planet Earth [ http://antwrp.gsfc.nasa.gov/apod/ap000420.html ]. Though ice covered [ http://spacescience.com/headlines/y2000/ ast22aug_1.htm ], the surface of Europa is thought to be geologically active, riding over a substantial ocean [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=1998Natur.391..363C&db_key=AST&high=3899d8d98211557 ] of liquid water. |
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North Pole Below
| Title |
North Pole Below |
| Explanation |
Orbiting over the north pole of planet Earth [ http://earthobservatory.nasa.gov/ ] on May 5, the MODIS instrument on-board the Terra spacecraft [ http://terra.nasa.gov/ ], recorded this view of the ice cap [ http://earthobservatory.nasa.gov/Newsroom/NewImages/ images.php3?img_id=4193 ] 700 kilometers below. A radial grid centered on the pole is shown on top of the approximately true color image where each pixel covers about one square kilometer. Frozen sea ice [ http://www.natice.noaa.gov/ ] appears whitish while open water or newly refrozen ice looks black. An impressive criss-crossing network of cracks in ice shifting above a liquid water ocean is visible, traced by the meandering dark lines. In fact, the dark network of cracks in the sea ice [ http://southport.jpl.nasa.gov/polar/iceinfo.html ] is reminiscent of another world in our solar system which may also harbor a liquid water ocean -- Jupiter's ice moon [ http://antwrp.gsfc.nasa.gov/apod/ap960813.html ] Europa [ http://galileo.jpl.nasa.gov/moons/europa.html ]. |
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Double Asteroid 90 Antiope
| Title |
Double Asteroid 90 Antiope |
| Explanation |
This eight-frame animation is based on the first ever images [ http://www.boulder.swri.edu/~merline/press/ ] of a double asteroid [ http://www.boulder.swri.edu/~merline/press/release.txt ]! Formerly thought to be a single enormous chunk of rock, asteroid 90 Antiope [ http://cfa-www.harvard.edu/iau/lists/ NumberedMPs00001.html ] resides in the solar system's [ http://space.jpl.nasa.gov/ ] main asteroid belt [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ asteroids.html ] between Mars and Jupiter. Now, these premier images reveal Antiope to actually consist of two 50 mile wide asteroids separated by about 100 miles. Like weights on each end of an elastic string, the pair mutually orbit [ http://hyperphysics.phy-astr.gsu.edu/hbase/ orbv.html#bo ] their center of mass, or balance point in the space between them, once every 16.5 hours. Binary asteroids and asteroids with moons [ http://antwrp.gsfc.nasa.gov/apod/ap991014.html ] are believed to be rare, but observations of their orbits allow a direct determination of asteroid masses and densities. Surprisingly, Antiope and known [ http://www.cfht.hawaii.edu/News/PR_001026/ ] asteroid-moon [ http://antwrp.gsfc.nasa.gov/apod/ap990807.html ] systems are found to have densities closer to ice than rock, despite their relatively dark and unreflective surfaces. These sharp images were made at the Keck Observatory atop the Hawaiian volcano Mauna Kea using newly developed adaptive optics [ http://www.mtwilson.edu/Science/ AdapOpt/Overview/ ] technology to overcome the blurring effect [ http://antwrp.gsfc.nasa.gov/apod/ap000725.html ] of Earth's atmosphere. |
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Oceans Under Jupiter's Moon
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| Title |
Oceans Under Jupiter's Moon Ganymede? |
| Explanation |
The search for extraterrestrial [ http://www.seti.org/ ] life came back into our own Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ] last week with the announcement [ http://www.jpl.nasa.gov/releases/2000/aguganymederoundup.html ] that there may be liquid oceans under the surface of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ]'s moon Ganymede [ http://www.jpl.nasa.gov/galileo/moons/ganymede.html ]. Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap000620.html ] now joins Callisto [ http://www.jpl.nasa.gov/galileo/news32.html ] and Europa [ http://www.jpl.nasa.gov/galileo/moons/europa.html ] as moons of Jupiter [ http://www.solarviews.com/eng/jupiter.htm ] that may harbor seas of liquid water under layers of surface ice [ http://antwrp.gsfc.nasa.gov/apod/ap980722.html ]. The ocean hypothesis surfaced as an explanation for Ganymede's unusually strong magnetic field [ http://www.igpp.ucla.edu/galileo/doc/n384/text.htm ]. Ganymede, the largest moon in the Solar System, also has the largest measured magnetic field [ http://www-spof.gsfc.nasa.gov/Education/Imagnet.html ] of any moon. Some exobiologists [ http://exobiology.nasa.gov/ssx/exobiology.html ] hypothesize that life may be able to emerge [ http://www.etext.org/Zines/Quanta/life.html ] in such an ocean, much as it did in the oceans of ancient Earth [ http://wwwcatsic.ucsc.edu/~eart1/Notes/Lec1.html ]. Above [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02583 ], a frame from a computer simulation [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenDownloadOpts.pl?PIA02583 ] shows what it would look like to fly over [ http://antwrp.gsfc.nasa.gov/apod/ap961025.html ] the surface of Ganymede, as extrapolated from photographs of the grooved moon [ http://antwrp.gsfc.nasa.gov/apod/ap960711.html ] taken by the robot spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/mission.html ] currently orbiting Jupiter. |
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Nashville Four Planet Skylin
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| Title |
Nashville Four Planet Skyline |
| Explanation |
So far this February, evening skies [ http://antwrp.gsfc.nasa.gov/apod/ap000504.html ] have been blessed with a glorious Moon and three bright planets, Venus [ http://www.library.utoronto.ca/utel/rp/poems/ longfe10.html ], Jupiter, and Saturn. But just last week, on January 30th, an extreme wide-angle lens allowed astrophotographer Larry Koehn to capture this twilight view of Moon and four planets above [ http://www.seds.org/nineplanets/nineplanets/ see.html ] Nashville, Tennessee, USA. These major solar system [ http://space.jpl.nasa.gov/ ] bodies lie along the ecliptic plane [ http://antwrp.gsfc.nasa.gov/apod/ap001014.html ] and so follow a diagonal line through the picture. Starting near the upper left corner is bright Jupiter [ http://starchild.gsfc.nasa.gov/docs/StarChild/ solar_system_level2/jupiter.html ], which takes on a slightly triangular shape due to the lens distortion. Just below and right of Jupiter is Saturn [ http://www.jpl.nasa.gov/cassini/english/kids/ saturn_in_sky.html ]. Continuing along the diagonal toward the lower right is an overexposed, six day old Moon [ http://www.inconstantmoon.com/ ] and brilliant Venus seemingly embedded in clouds. The fourth planet pictured is Mercury. Notoriously hard to see from planet Earth because it never wanders far from the Sun, Mercury is [ http://antwrp.gsfc.nasa.gov/apod/ap991111.html ] visible just above the lower right corner. The line from Jupiter to Mercury spans about 92 degrees across the Nashville sky. |
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Great Mountain Moonrise
| Title |
Great Mountain Moonrise |
| Explanation |
On May 31st, a gorgeous Full Moon rose over Uludag Mountain [ http://en.wikipedia.org/wiki/Uluda%C4%9F ] in Bursa Province, Turkey. This alluring telephoto view of the twilight [ http://antwrp.gsfc.nasa.gov/apod/ap050611.html ] scene is a composite of images taken roughly every two minutes beginning shortly after Sunset, following the rising Moon as it moves up and to the right. Of course, as the Moon rises it gets brighter and changes color, becoming less reddened [ http://webexhibits.org/causesofcolor/14B.html ] as the sight-line through the dense atmosphere [ http://www.atoptics.co.uk/ ] is steadily reduced. Each of the final two exposures also captured a rising planet Jupiter. Like the Full Moon [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/ question3.html ], the bright, wandering planet is nearly opposite [ http://www.heavens-above.com/gloss.asp?term=opposition ] the Sun in Earth's sky and was caught on the lefthand side of the picture in two places, just above a small peak in the mountain side. Intriguingly, some considered this Full Moon a Blue Moon [ http://science.nasa.gov/headlines/y2007/ 30may_bluemoon.htm ]. |
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Looking Back at an Eclipsed
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| Title |
Looking Back at an Eclipsed Earth |
| Explanation |
Here is what the Earth looks like during a solar eclipse [ http://www.mreclipse.com/Special/SEprimer.html ]. The shadow of the Moon [ http://antwrp.gsfc.nasa.gov/apod/ap040829.html ] can be seen darkening part of Earth. This shadow [ http://antwrp.gsfc.nasa.gov/apod/ap031127.html ] moved across the Earth [ http://antwrp.gsfc.nasa.gov/apod/earth.html ] at nearly 2000 kilometers per hour. Only observers near the center of the dark circle [ http://antwrp.gsfc.nasa.gov/apod/ap031208.html ] see a total solar eclipse - others see a partial eclipse where only part of the Sun appears blocked by the Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010408.html ]. This spectacular picture [ http://theastropages.com/articles/articles011.htm ] of the 1999 August 11 solar eclipse [ http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html ] was one of the last ever taken from the Mir [ http://antwrp.gsfc.nasa.gov/apod/ap040327.html ] space station. The two bright spots that appear on the upper left are possibly Jupiter and Saturn [ http://theastropages.com/articles/articles011.htm ], although this has yet to be proven. Mir was deorbited [ http://antwrp.gsfc.nasa.gov/apod/ap010323.html ] in a controlled re-entry in 2001. |
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Io: Moon Over Jupiter
| Title |
Io: Moon Over Jupiter |
| Explanation |
How big is the Jovian moon Io [ http://www.seds.org/nineplanets/ nineplanets/io.html ]? The most volcanic body [ http://volcano.und.nodak.edu/vwdocs/planet_volcano/ other_worlds.html ] in the Solar System, Io (usually pronounced "EYE-oh") is 3,600 kilometers in diameter, about the size of planet Earth's single large natural satellite [ http://antwrp.gsfc.nasa.gov/apod/ap010127.html ]. Gliding past Jupiter [ http://www.jpl.nasa.gov/jupiterflyby/ ] at the turn of the millennium, the Cassini spacecraft captured this awe inspiring view [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] of active Io [ http://www.jpl.nasa.gov/galileo/moons/io.html ] with the largest [ http://www.seds.org/nineplanets/nineplanets/ datamax.html ] gas giant as a backdrop, offering a stunning demonstration of the ruling planet's relative size [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ jupiterfact.html ]. Although in the picture Io [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02879 ] appears to be located just in front of the swirling Jovian clouds, Io hurtles around its orbit once every 42 hours at a distance of 420,000 kilometers or so from the center of Jupiter [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ joviansatfact.html ]. That puts it nearly 350,000 kilometers above Jupiter's cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap010215.html ], roughly equivalent to the distance between Earth and Moon [ http://antwrp.gsfc.nasa.gov/apod/ap980904.html ]. The Cassini spacecraft [ http://www.jpl.nasa.gov/cassini/english/spacecraft/ ] itself was about 10 million kilometers from Jupiter when recording the image data. |
|
Astronomer's Moon
| Title |
Astronomer's Moon |
| Explanation |
Jupiter is [ http://www.nineplanets.org/jupiter.html ] an astronomer's planet -- its large size and contrasting global cloud belts and zones [ http://antwrp.gsfc.nasa.gov/apod/ap030906.html ] allow detailed studies with a range of earthbound telescopes [ http://www.lpl.arizona.edu/alpo/ ]. On the other hand, most telescopic views of Jupiter's moons [ http://antwrp.gsfc.nasa.gov/apod/ap030227.html ] usually show only featureless, tantalizing points of light hovering near the ruling gas giant. But this impressive picture from a small, ground-based telescope reveals a stunning amount of detail [ http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/ Number/1752001/page/0/view/collapsed/sb/5/o/all/fpart/1 ] on Ganymede, a jovian moon about the same size as Earth's moon but at least 1,500 times farther away. The image was carefully constructed by combining and processing only the 409 sharpest frames from a total of 10,000 recorded at 30 frames per second by a digital camera. Ganymede's [ http://www.nineplanets.org/ganymede.html ] radius is about 2,600 kilometers indicating that the surface markings [ http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=503&vbody=399 &month=6&day=30&year=2007&hour=20&minute=05&rfov=2&fovmul=-1&bfov=30 &porbs=1&showsc=1 ] visible are as small as around 900 kilometers across. |
|
Oceans Under Jupiter's Calli
…
| Title |
Oceans Under Jupiter's Callisto? |
| Explanation |
Why does Jupiter [ http://www.nineplanets.org/jupiter.html ]'s moon Callisto [ http://www.nineplanets.org/callisto.html ] alter the magnetic field [ http://www-istp.gsfc.nasa.gov/Education/Imagnet.html ] of Jupiter in its vicinity? Callisto itself does not have a strong magnetic field. One possible answer is that Callisto [ http://www.solarviews.com/eng/callisto.htm ] harbors sub-surface oceans of electrically conducting salt-water [ http://www.room103.com/archive/q_saltconductivity.htm ]. This hypothesis was bolstered recently [ http://www.nature.com/nsu/010726/010726-12.html ] by a new analysis of how Callisto creates and dissipates heat. Callisto [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA00362 ] is thought to create heat by the radioactive decay [ http://home.a-city.de/walter.fendt/phe/lawdecay.htm ] of internal rock -- a process that keeps the Earth's mantle [ http://earth.leeds.ac.uk/~greg/Conv.html ] molten. Callisto may not be able to dissipate this heat very efficiently, however, as it has thick layers of ice and rock on its surface. Perhaps this heat is enough to keep sub-surface water from freezing into ice. With this hypothesis [ http://space.com/scienceastronomy/solarsystem/callisto_water_010726.html ], Callisto joins two other of Jupiter's moons, Europa [ http://antwrp.gsfc.nasa.gov/apod/ap980310.html ] and Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap001218.html ], in candidates for sub-surface oceans. Callisto's oceans, however, might prove too hostile to support Earth-like life [ http://www.bbc.co.uk/education/darwin/loe/ ]. |
|
The 47 Ursae Majoris System
| Title |
The 47 Ursae Majoris System |
| Explanation |
Watching and waiting [ http://exoplanets.org/ ], astronomers have uncovered the presence of more than 70 planets orbiting stars other than the Sun. So far almost all these extrasolar planets [ http://cfa-www.harvard.edu/planets/ ] have crazy elongated orbits, lie uncomfortably close to their parent stars, or are found in bizarre, inhospitable systems. Yet a reported new planet [ http://www.nsf.gov/od/lpa/news/press/01/ pr0164.htm ] discovery indicates for the first time that a nearby sun-like star, 47 Ursae Majoris (47 UMa), has at least two planets in nearly circular orbits more reminiscent of Jupiter [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ jupiterfact.html ] and Saturn [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ saturnfact.html ] in our own familiar Solar System [ http://www.jpl.nasa.gov/basics/bsf1-1.html ]. The planets are too distant and faint to be photographed directly. Still, 13 years of [ http://exoplanets.org/esp/47uma/47uma.shtml ] spectroscopic observations of 47 UMa have revealed the wobbling [ http://exoplanets.org/doppler.html ] signature of a second planet intertwined with [ http://exoplanets.org/esp/47uma/47uma.shtml ] one previously known. In this artist's illustration [ http://extrasolar.spaceart.org/extrasol.html ], the worlds of 47 UMa [ http://antwrp.gsfc.nasa.gov/apod/ap971005.html ] hang over the rugged volcanic landscape of a hypothetical moon. The moon orbits the newly discovered planet [ http://exoplanets.org/esp/47uma/47uma_announce.html ], imagined here with Saturn-like rings, while the previously known planet is visible as a tiny crescent, close to the yellowish star. Closer still to 47 UMa is another tiny dot, a hypothetical [ http://www.fourmilab.to/terranova/ terranova.html ] Earth-like water world [ http://antwrp.gsfc.nasa.gov/apod/ap980530.html ]. About 51 light-years distant, 47 UMa can be found in planet Earth's sky near the Big Dipper [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Ursa_Major.html ]. |
|
Gibbous Europa
| Title |
Gibbous Europa |
| Explanation |
Although the phase [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ] of this moon might appear familiar, the moon itself might not. In fact, this gibbous phase [ http://en.wikipedia.org/wiki/Gibbous ] shows part of Jupiter [ http://www.nineplanets.org/jupiter.html ]'s moon Europa [ http://www.nineplanets.org/europa.html ]. The robot spacecraft Galileo [ http://en.wikipedia.org/wiki/ Galileo_%28spacecraft%29 ] captured this image [ http://planetimages.blogspot.com/2005/09/ new-color-views-of-europa.html ] mosaic during its mission orbiting Jupiter from 1995 - 2003. Visible are plains [ http://antwrp.gsfc.nasa.gov/apod/ap981215.html ] of bright ice [ http://antwrp.gsfc.nasa.gov/apod/ap000418.html ], cracks [ http://antwrp.gsfc.nasa.gov/apod/ap980310.html ] that run to the horizon, and dark patches [ http://antwrp.gsfc.nasa.gov/apod/ap970815.html ] that likely contain both ice and dirt. Raised terrain [ http://antwrp.gsfc.nasa.gov/apod/ap980303.html ] is particularly apparent near the terminator [ http://en.wikipedia.org/wiki/ Terminator_%28solar%29 ], where it casts shadows [ http://antwrp.gsfc.nasa.gov/apod/ap001225.html ]. Europa [ http://antwrp.gsfc.nasa.gov/apod/ap961120.html ] is nearly the same size as Earth's Moon [ http://antwrp.gsfc.nasa.gov/apod/ap020127.html ], but much smoother, showing few highlands [ http://csep10.phys.utk.edu/astr161/lect/moon/ moon_surface.html ] or large impact craters [ http://antwrp.gsfc.nasa.gov/apod/ap010809.html ]. Evidence and images from the Galileo spacecraft [ http://solarsystem.nasa.gov/galileo/ ], indicated that liquid oceans might exist [ http://antwrp.gsfc.nasa.gov/apod/ap980102.html ] below the icy surface. To test speculation that these seas hold life, ESA [ http://en.wikipedia.org/wiki/European_Space_Agency ] has started preliminary development of the Jovian Europa Orbiter [ http://www.jpl.nasa.gov/europaorbiter/europao.htm ], a spacecraft proposed to orbit Europa. If the surface ice is thin enough, a future mission might drop hydrobots [ http://www.jpl.nasa.gov/galileo/mission/ journey-future.html ] to burrow into the oceans and search for life. |
|
A Portrait of Saturn from Ti
…
| Title |
A Portrait of Saturn from Titan |
| Explanation |
This artistic portrait [ http://sci.esa.int/content/searchimage/ searchresult.cfm?aid=12&cid=387&ooid=18425 ] of Saturn [ http://www.otenet.gr/everyday/ saturday.html ] depicts how it might look from Titan [ http://www.seds.org/nineplanets/nineplanets/ titan.html ], Saturn's largest moon. In the foreground sits ESA's Huygens probe [ http://sci.esa.int/home/huygens/index.cfm ], which will be released by NASA's Cassini spacecraft [ http://www.jpl.nasa.gov/cassini/english/spacecraft/ ] and parachute to Titan's surface. Cassini will [ http://www.jpl.nasa.gov/cassini/english/ ] reach Saturn in 2004 and release the Huygens probe [ http://www.jpl.nasa.gov/cassini/english/spacecraft/ probe.html ] later that year. Titan [ http://antwrp.gsfc.nasa.gov/apod/ap000820.html ] is one of only two moons in the Solar System [ http://space.jpl.nasa.gov ] to have an atmosphere. It has been suggested Titan might have gasoline-like lakes and an atmospheric chemistry like that [ http://www.llnl.gov/str/Macintosh.html ] found on early Earth. The Cassini spacecraft was launched in October 1997 [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] and has now traveled beyond Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap010808.html ]. |
|
Ganymede: Torn Comet - Crate
…
| Title |
Ganymede: Torn Comet - Crater Chain |
| Explanation |
This striking line of 13 closely spaced craters [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA01610 ] on Jupiter's moon Ganymede [ http://cass.jsc.nasa.gov/pub/research/outerp/gany.html ] was photographed by the Galileo spacecraft in 1997. The picture covers an area about 120 miles wide and the chain of craters cuts across a sharp boundary between dark and light terrain. What caused this crater chain? Remarkably, the exploration of the Solar System [ http://sse.jpl.nasa.gov/index.html ], has shown that crater chains [ http://antwrp.gsfc.nasa.gov/apod/ap950715.html ] like this one are not unique [ http://neo.jpl.nasa.gov/images/moon.html ], though they were [ http://stardust.jpl.nasa.gov/news/news12.html ] considered mysterious until a dramatic object lesson was offered by comet Shoemaker-Levy 9. In 1994 many denizens of planet Earth [ http://antwrp.gsfc.nasa.gov/apod/ap971026.html ] watched as huge pieces of this torn comet [ http://antwrp.gsfc.nasa.gov/apod/ap990814.html ] slammed into Jupiter itself in a spectacular series of sequential impacts [ http://antwrp.gsfc.nasa.gov/apod/ap980804.html ]. It is very likely that similar torn comets from the early history of the Solar System are responsible for this and other crater chains [ http://astrosun.tn.cornell.edu/staff/bottke/crater_chain/ chain.html ]. |
|
Io: A Volcanic Moon
| Title |
Io: A Volcanic Moon |
| Explanation |
In 1610, Galileo [ http://bang.lanl.gov/video/stv/arshtml/arstoc.html ] turned his telescope to the heavens and discovered that the planet Jupiter had four bright moons. The innermost of these Galilean moons, Io [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/io.html ], turned out to be one of the most exotic objects in the solar system. About the size of the earth's moon, Io is covered with volcanoes, many of which are currently active. The material expelled in the volcanic eruptions may contain compounds of Sulfur which take on a variety of colors and could account for its mottled, "pizza-like" appearance. For a report of a recent eruption of an Io volcano, see the NASA Infrared Telescope Facility press release [ http://seawifs.gsfc.nasa.gov/JASON/IO_DATA/IMAGES/iooutburst.txt ] and photo . Tomorrow's picture: Closeup of an Io Volcano. |
|
Crescent Europa
| Title |
Crescent Europa |
| Explanation |
Although the phase [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ] of this moon might appear familiar, the moon itself might not. In fact, this crescent shows part of Jupiter [ http://www.nineplanets.org/jupiter.html ]'s moon Europa [ http://www.nineplanets.org/europa.html ]. The passing robot spacecraft Voyager 2 [ http://vraptor.jpl.nasa.gov/voyager/vgrfaqs.html ] captured this image [ http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-000469.html ] in 1979. Visible are plains [ http://antwrp.gsfc.nasa.gov/apod/ap981215.html ] of bright ice [ http://antwrp.gsfc.nasa.gov/apod/ap000418.html ], cracks [ http://antwrp.gsfc.nasa.gov/apod/ap980310.html ] that run to the horizon, and dark patches [ http://antwrp.gsfc.nasa.gov/apod/ap970815.html ] that likely contain both ice and dirt. Raised terrain [ http://antwrp.gsfc.nasa.gov/apod/ap980303.html ] is particularly apparent near the terminator [ http://calspace.ucsd.edu/edout/gloss/tgloss.html#terminator ], where it casts shadows [ http://antwrp.gsfc.nasa.gov/apod/ap001225.html ]. Europa [ http://antwrp.gsfc.nasa.gov/apod/ap961120.html ] is nearly the same size as Earth's Moon [ http://antwrp.gsfc.nasa.gov/apod/ap020127.html ], but much more smooth, showing few highlands [ http://csep10.phys.utk.edu/astr161/lect/moon/moon_surface.html ] or large impact craters [ http://antwrp.gsfc.nasa.gov/apod/ap010809.html ]. Evidence and images from the Galileo spacecraft [ http://galileo.jpl.nasa.gov/mission/space-intro.html ], currently orbiting Jupiter [ http://galileo.jpl.nasa.gov/mission/mission.html ], indicate that liquid oceans might exist [ http://antwrp.gsfc.nasa.gov/apod/ap980102.html ] below the icy surface. To test speculation that these seas hold life, NASA [ http://www.nasa.gov/ ] has started preliminary development of the Europa Orbiter [ http://www.jpl.nasa.gov/europaorbiter/europao.htm ], a spacecraft that would use radar [ http://www.howstuffworks.com/radar.htm ] to help determine the thickness of the surface ice. If the surface ice is thin enough, a future mission might drop hydrobots [ http://www.jpl.nasa.gov/galileo/mission/journey-future.html ] to burrow into the oceans and search for life. |
|
Ganymede: Moonquake World
| Title |
Ganymede: Moonquake World |
| Explanation |
Ganymede [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ganymede.html ] probably undergoes frequent ground shaking events not unlike terrestrial earthquakes. Ganymede [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/ganymede.html ], the largest moon of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950625.html ] and the Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ], has a thick outer coating of water ice. Passing Voyager spacecraft found a large number of cracks and grooves in the ice so it is thought that Ganymede, like the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ], has large shifting surface masses called tectonic plates. Ganymede was discovered by Galileo [ http://galileo.imss.firenze.it/museo/4/index.html ] and Marius [ http://seds.lpl.arizona.edu/billa/tnp/help.html#M ] in 1610, and is larger than the planets Mercury and Pluto. The NASA spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/ ] is scheduled to arrive at Jupiter is December of 1995. Tomorrow's picture: Europa: Ancient Water World |
|
Europa: Ancient Water World
| Title |
Europa: Ancient Water World |
| Explanation |
Beneath the cold icy surface of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950625.html ]'s moon Europa [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/europa.html ] are probably the only oceans of water in our Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ] outside of Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ]. These oceans, possibly 50 kilometers deep, might also be the most likely local place to find extra-terrestrial life. Europa [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/europa.html ]'s smooth surface is unlike any other known planet or moon, giving evidence for relatively few craters or mountains. Europa was discovered by Galileo [ http://galileo.imss.firenze.it/museo/4/index.html ] and Marius [ http://seds.lpl.arizona.edu/billa/tnp/help.html#M ] in 1610. The NASA spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/ ] is scheduled to arrive at Jupiter in December of 1995. Tomorrow's picture: Callisto: Dark Smashed Iceball |
|
The Colorful Moon
| Title |
The Colorful Moon |
| Explanation |
Do you recognize the Earth's Moon [ http://www.seds.org/nineplanets/nineplanets/ luna.html ] when you see it? The crazy, patchwork appearance of the false-color image [ http://photojournal-b.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA00132 ] makes this almost full view of the Moon's [ http://www.xs4all.nl/~carlkop/golf.html ] familiar near side [ http://antwrp.gsfc.nasa.gov/apod/ap981008.html ] look very strange. The Sea of Tranquillity (Mare Tranquillitatis [ http://volcano.und.nodak.edu/vwdocs/planet_volcano/lunar/ mare/mlm.html ]) is the bright blue area at right, the Ocean of Storms (Oceanus Procellarum) is the extensive blue and orange area on the left, and white lines radiate from the crater Tycho [ http://antwrp.gsfc.nasa.gov/apod/ap010809.html ] at bottom center. Recorded in 1992 by the Galileo spacecraft enroute to Jupiter, the picture is a mosaic of 15 images taken through three color filters. The image data were combined in an exaggerated color scheme to emphasize composition differences [ http://antwrp.gsfc.nasa.gov/apod/ap960601.html ] - blue hues reveal titanium rich areas while orange and purple colors show regions relatively poor in titanium and iron. Multicolor images exploring the Moon's [ http://www.lpi.usra.edu/publications/slidesets/ clem2nd.html ] global surface composition were made in 1994 by the Clementine spacecraft. |
|
Dusk of the Planets
| Title |
Dusk of the Planets |
| Explanation |
A great grouping of planets [ http://www.nineplanets.org/ ] is now visible [ http://CarnegieScienceCenter.org/exhibits/planet_calendar.asp ] to the west just after sunset. Over the next two weeks, Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap010819.html ], Venus [ http://antwrp.gsfc.nasa.gov/apod/ap010916.html ], Earth, Mars [ http://antwrp.gsfc.nasa.gov/apod/ap010628.html ], Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap020205.html ], and Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap020215.html ] -- the innermost six planets of our Solar System [ http://www.nineplanets.org/overview.html ] -- can be seen in a single knowing glance. The image on the left [ http://www.astropix.com/HTML/H_OTHER/PLANETS.HTM ] captured them all in one frame. Connecting the planetary dots delineates the edge-on ecliptic [ http://antwrp.gsfc.nasa.gov/apod/ap990529.html ], the plane in which the planets orbit the Sun [ http://csep10.phys.utk.edu/astr161/lect/retrograde/copernican.html ]. The shot was taken on April 23 near Chatsworth, New Jersey [ http://www.state.nj.us/ ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ], and even includes scattered light from the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap000403.html ] and the Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ]. Besides the planets, the Pleiades [ http://antwrp.gsfc.nasa.gov/apod/ap010506.html ] and Hyades [ http://www.astro.uiuc.edu/~kaler/sow/hyades-p.html ] open clusters [ http://www.seds.org/messier/open.html ] of stars are visible [ http://www.planetary.org/html/news/articlearchive/headlines/2002/alignment.htm ]. |
|
Love and War by Moonlight
| Title |
Love and War by Moonlight |
| Explanation |
Venus [ http://www.pantheon.org/articles/v/venus.html ], named for the Roman goddess of love, and Mars [ http://www.pantheon.org/articles/m/mars.html ], the war god's namesake, approach each other by moonlight [ http://www.thorstenkaye.com/tk_todayspoem3.htm#BM41 ] in this lovely sky view recorded on May 14th from Dunkirk, Maryland, USA. The four second time exposure made in twilight with a digital camera also records earthshine [ http://antwrp.gsfc.nasa.gov/apod/ap020419.html ] illuminating the otherwise dark surface of the young [ http://starchild.gsfc.nasa.gov/docs/StarChild/ StarChild.html ] crescent Moon. Venus shines as the third brightest object in Earth's sky, after the Sun and the Moon itself, and has been appearing as the brilliant evening star [ http://www.library.utoronto.ca/utel/rp/poems/ longfe10.html ] in the pantheon of planets [ http://www.seds.org/nineplanets/nineplanets/ nineplanets.html ] arrayed in the west during April and May. Here, Venus' light is so intense that it produces a noticeable spike in the sensitive camera's image. Much fainter Mars [ http://www-mgcm.arc.nasa.gov/mgcm/fun/ ancient_mars.html ] is lower in the picture, caught between tree limbs swaying in a gentle evening breeze. By early June, Mars will be harder to spot as it wanders toward the horizon, but Venus and father Jupiter [ http://www.pantheon.org/articles/j/jupiter.html ] will draw closer together, presenting a spectacular pair of bright planets in the west [ http://SkyandTelescope.com/observing/objects/planets/ article_572_1.asp ]. |
|
Planets Over Stonehenge
| Title |
Planets Over Stonehenge |
| Explanation |
Stonehenge [ http://antwrp.gsfc.nasa.gov/apod/ap990912.html ], four thousand year old [ http://antwrp.gsfc.nasa.gov/apod/ap980408.html ] monument to the Sun [ http://www.hao.ucar.edu/public/education/archeoslides/ index.html ], provides an appropriate setting for this delightful snapshot [ http://www.astrocruise.com/planets.htm ] of the Sun's children [ http://www.seds.org/nineplanets/nineplanets/ ] gathering in planet Earth's sky. While the massive stone [ http://www.amherst.edu/~ermace/sth/poetry.html ] structure dates from around 2000 B.C. [ http://mathforum.org/dr.math/problems/masell10.1.97.html ], this arrangement of the visible planets [ http://skyandtelescope.com/observing/objects/planets/ article_572_1.asp ] was recorded only a few days ago on the evening of May 4th, 2002 A.D. Bright Jupiter stands highest above the horizon at the upper left. A remarkable, almost equilateral triangle [ http://mathforum.org/dr.math/faq/formulas/ faq.triangle.html ] formed by Saturn (left), Mars (top), and Venus (right) is placed just above the stones near picture center. Fighting the glow of the setting sun, Mercury can be spotted closest to the horizon, below and right of the planetary triad. Still easy to enjoy [ http://science.nasa.gov/headlines/y2002/24apr_relax.htm ] for casual sky gazers, this photogenic and slowly shifting planetary grouping [ http://science.nasa.gov/spaceweather/planets/ gallery_may02.html ] will be joined by a young crescent [ http://antwrp.gsfc.nasa.gov/apod/ap020419.html ] Moon beginning Monday, May 13. |
|
Natural Saturn On The Cassin
…
| Title |
Natural Saturn On The Cassini Cruise |
| Explanation |
What could you see approaching Saturn [ http://www.jpl.nasa.gov/cassini/Kids/stories/ ] aboard an interplanetary cruise [ http://www.jpl.nasa.gov:80/cassini/Mission/ cruise.html ] ship? Your view would likely resemble this subtly shaded image [ http://oposite.stsci.edu/pubinfo/pr/1998/28/b.html ] of the gorgeous ringed gas giant. Processed by the Hubble Heritage [ http://heritage.stsci.edu/ ] project, the picture intentionally avoids overemphasizing color contrasts and presents a natural looking Saturn [ http://heritage.stsci.edu/ public/Oct22/saturn/saturntable.html#caption ] with cloud bands, storms [ http://antwrp.gsfc.nasa.gov/apod/ap951018.html ], nearly edge-on rings [ http://antwrp.gsfc.nasa.gov/apod/ap981018.html ], and the small round shadow of the moon Enceladus near the center of the planet's disk. Of course, seats were not available on the only ship currently enroute, the Cassini spacecraft [ http://saturn.jpl.nasa.gov/cassini/index.shtml ]. Cassini flew by Jupiter [ http://www.jpl.nasa.gov/jupiterflyby/ ] at the turn of the millennium and is scheduled to [ http://saturn.jpl.nasa.gov/cassini/english/where/ ] arrive at Saturn in the year 2004. After an extended cruise to a world 1,400 million kilometers from the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ], Cassini will tour the Saturnian system [ http://www.seds.org/nineplanets/nineplanets/saturn.html ], conducting a remote, robotic exploration with software and instruments designed by [ http://www.jpl.nasa.gov/cassini/Partners/ ] denizens of planet Earth. |
|
Cracks and Ridges on Europa
| Title |
Cracks and Ridges on Europa |
| Explanation |
Which way to the interstate [ http://www.gbcnet.com/ushighways/history.html ]? What appears to be a caricature of a complex highway system on Earth [ http://antwrp.gsfc.nasa.gov/apod/ap010204.html ] is actually a system of ridges and cracks on the icy surface of Jupiter's moon Europa [ http://www.solarviews.com/eng/europa.htm ]. The distance between parallel ridges in the above photograph [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA01178 ] is typically about 1 kilometer. The complexity of the cracks [ http://antwrp.gsfc.nasa.gov/apod/ap961022.html ] and ridges [ http://antwrp.gsfc.nasa.gov/apod/ap981215.html ] tell a story of Europa [ http://www.jpl.nasa.gov/galileo/moons/europa.html ]'s past that is mostly undecipherable -- planetary geologists try to understand just the general origin of the overall features. One noteworthy feature [ http://antwrp.gsfc.nasa.gov/apod/ap980609.html ] is the overall white sheen, possibly indicating the presence of frost. Another is the dark centers between parallel ridges, which might indicate that dirty water from an underground ocean [ http://antwrp.gsfc.nasa.gov/apod/ap970409.html ] recently welled up in the cracks and froze. Recent research indicates that enough carbon [ http://pearl1.lanl.gov/periodic/elements/6.html ] exists to support an underwater biosphere [ http://www.seti-inst.edu/general/press_release/europa_05_21_02.html ], but that Europa's ice crust [ http://unisci.com/stories/20014/1109013.htm ] may be over three kilometers thick in some places. |
|
Io: Moon Over Jupiter
| Title |
Io: Moon Over Jupiter |
| Explanation |
How big is the Jovian moon Io [ http://www.seds.org/nineplanets/ nineplanets/io.html ]? The most volcanic body [ http://volcano.und.nodak.edu/vwdocs/planet_volcano/ other_worlds.html ] in the Solar System, Io (usually pronounced "EYE-oh") is 3,600 kilometers in diameter, about the size of planet Earth's single large natural satellite [ http://antwrp.gsfc.nasa.gov/apod/ap010127.html ]. Gliding past Jupiter [ http://www.jpl.nasa.gov/jupiterflyby/ ] at the turn of the millennium, the Cassini spacecraft captured this awe inspiring view [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] of active Io [ http://www.jpl.nasa.gov/galileo/moons/io.html ] with the largest [ http://www.seds.org/nineplanets/nineplanets/ datamax.html ] gas giant as a backdrop, offering a stunning demonstration of the ruling planet's relative size [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ jupiterfact.html ]. Although in the picture Io [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02879 ] appears to be located just in front of the swirling Jovian clouds, Io hurtles around its orbit once every 42 hours at a distance of 420,000 kilometers or so from the center of Jupiter [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ joviansatfact.html ]. That puts it nearly 350,000 kilometers above Jupiter's cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap010215.html ], roughly equivalent to the distance between Earth and Moon [ http://antwrp.gsfc.nasa.gov/apod/ap980904.html ]. The Cassini spacecraft [ http://saturn.jpl.nasa.gov/cassini/english/spacecraft/ ] itself was about 10 million kilometers from Jupiter when recording the image data. |
|
Stereo Saturn
| Title |
Stereo Saturn |
| Explanation |
Get out your red/blue glasses [ http://mpfwww.jpl.nasa.gov/MPF/mpf/glasses.html ] and launch [ http://beacon.jpl.nasa.gov/exhibits/voyager/ default.html ] yourself into this stereo [ http://cass.jsc.nasa.gov/research/stereo_atlas/ SS3D.HTM ] picture of Saturn! The picture is actually composed from two images recorded weeks apart by the Voyager 2 spacecraft [ http://nssdc.gsfc.nasa.gov/database/ MasterCatalog?sc=1977-076A ] during its visit to [ http://sse.jpl.nasa.gov/missions/sat_missns/ sat-voy2.html ] the Saturnian System in August of 1981. Traveling at about 35,000 miles per hour, the spacecraft's changing viewpoint from one image to the next produced this exaggerated but pleasing stereo effect [ http://antwrp.gsfc.nasa.gov/apod/ap970404.html ]. Saturn is the second largest planet [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ saturn.html ] in the Solar System, after Jupiter. Its spectacular ring system [ http://ringmaster.arc.nasa.gov/saturn/saturn.html ] is so wide that it would span the space between the Earth and Moon. Although they look solid here, Saturn's [ http://antwrp.gsfc.nasa.gov/apod/ap000129.html ] rings consist of individually orbiting bits of ice and rock ranging in size from grains of sand to barn-sized boulders. |
|
Jupiter, Moons and Bees
| Title |
Jupiter, Moons and Bees |
| Explanation |
Rising before the Sun on September 4, Jupiter and an old cresent Moon [ http://antwrp.gsfc.nasa.gov/apod/ap020419.html ] gathered in the dim constellation of Cancer [ http://www.coldwater.k12.mi.us/lms/planetarium/myth/ cancer.html ]. Watching from a hillside near Austin, Texas, planet Earth [ http://earthobservatory.nasa.gov/ ], astrophotographer Russell Croman recorded this view [ http://www.rc-astro.com/solar_system/moon/moonbees.html ] of their passing as clouds gracefully dimmed the brilliant moonlight. Earthshine illuminates [ http://www.amnh.org/exhibitions/codex/2A2r.html ] the lunar night side and on close inspection, bright Jupiter at the lower right appears tightly flanked [ http://antwrp.gsfc.nasa.gov/apod/ap980513.html ] by its own four large Galilean moons [ http://www.jpl.nasa.gov/galileo/ganymede/ discovery.html ]. Next to Jupiter lies a loose swarm of stars just below the clouds. The stars are the brighter members of the nearby star cluster M44, popularly known as the Beehive cluster [ http://antwrp.gsfc.nasa.gov/apod/ap980803.html ]. Croman's remarkable digital image has been processed only slightly to improve the visibility of the earthshine region and Jupiter's moons [ http://antwrp.gsfc.nasa.gov/apod/ap001118.html ]. |
|
Jupiter, Io and Shadow
| Title |
Jupiter, Io and Shadow |
| Explanation |
Pictured above [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02860 ] is the innermost of Jupiter's Galilean satellites [ http://www.jpl.nasa.gov/galileo/ganymede/ discovery.html ], Io, superposed in front of the gas giant planet. To the left of Io [ http://www.seds.org/nineplanets/nineplanets/io.html ] is a dark spot that is Io's own shadow. A solar eclipse [ http://antwrp.gsfc.nasa.gov/apod/ap021206.html ] would be seen from within the shadow spot on Jupiter. Viewed from [ http://space.jpl.nasa.gov ] planet Earth, similar shadows of Jupiter's large moons can often be seen crossing [ http://antwrp.gsfc.nasa.gov/apod/ap980202.html ] the giant planet's disk. But during the next several months, the Galilean moons can also be seen crossing in front of each other [ http://skyandtelescope.com/observing/objects/planets/ article_771_1.asp ] as, for a while, their orbits lie nearly edge-on when viewed [ http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=105&vbody=3&month=12&day=20¢ury=20&decade=0&year=2&hour=21&minute=35&rfov=30&fovmul=-1&bfov=30 ] by earthbound observers. This true-color contrast-enhanced image was taken [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] two years ago by the robot spacecraft Cassini, as it passed Jupiter on its way [ http://antwrp.gsfc.nasa.gov/apod/ap021104.html ] to Saturn in 2004. |
|
Io Volcano Culann Patera
| Title |
Io Volcano Culann Patera |
| Explanation |
What causes the unusual colors surrounding Io's volcanoes? Io [ http://www.nineplanets.org/io.html], the innermost large moon [ http://www.jpl.nasa.gov/galileo/ganymede/discovery.html ] of Jupiter [ http://www.solarviews.com/eng/jupiter.htm ], is known to be the most tumultuous body [ http://antwrp.gsfc.nasa.gov/apod/ap010715.html ] in the Solar System [ http://www.nineplanets.org/overview.html ]. Approximately the size of Earth's Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ], Io undergoes nearly continuous volcanic eruptions [ http://antwrp.gsfc.nasa.gov/apod/ap000606.html ] from an interior heated by gravitational tides [ http://burro.astr.cwru.edu/Academics/Astr221/Gravity/tides.html ] from Jupiter and Jupiter's other large moons. The robot spacecraft Galileo [ http://galileo.jpl.nasa.gov/mission/space-intro.html ] currently orbiting Jupiter has been monitoring the active volcano Culann Patera [ http://pirlwww.lpl.arizona.edu/missions/Galileo/releases/19May_i25culann.html ] over the past few years. The above images [ http://photojournal.jpl.nasa.gov/catalog/PIA03885 ] indicate that the volcano [ http://volcano.und.nodak.edu/volcanoes.html ] has produced not only red and black colored lava flows [ http://volcanoes.usgs.gov/Hazards/What/Lava/lavaflow.html ], but yellow sulfur [ http://pearl1.lanl.gov/periodic/elements/16.html ] patches from explosive plumes. Green colors may arise when these processes affect the same terrain. White patches may be caused, in part, by sulfur dioxide [ http://www.epa.gov/air/aqtrnd95/so2.html ] snow. As Galileo [ http://nssdc.gsfc.nasa.gov/planetary/galileo.html ] has fulfilled its mission objectives [ http://antwrp.gsfc.nasa.gov/apod/ap021218.html http://nssdc.gsfc.nasa.gov/planetary/galileo.html#objective ] and is running low on maneuvering fuel, NASA plans to crash [ http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=392 ] the spacecraft into Jupiter during 2003. |
|
Io at Sunset
| Title |
Io at Sunset |
| Explanation |
How tall are mountains on Jupiter [ http://www.nineplanets.org/jupiter.html ]'s moon Io [ http://www.solarviews.com/eng/io.htm ]? One way to find out is to view them at sunset [ http://antwrp.gsfc.nasa.gov/apod/ap021110.html ]. Tall structures facing the Sun [ http://www.nineplanets.org/sol.html ] are then better-lit and cast long shadows [ http://antwrp.gsfc.nasa.gov/apod/ap990830.html ]. The above image [ http://photojournal.jpl.nasa.gov/catalog/PIA03886 ] highlights Mongibello Mons [ http://planetarynames.wr.usgs.gov/jupiter/iomons.html ] on the far left, a sharp ridge rising so high [ http://antwrp.gsfc.nasa.gov/apod/ap020723.html ] it would rank among the highest mountains [ http://www.highalpex.com/Peaklist/peaklist.html ] on Earth [ http://antwrp.gsfc.nasa.gov/apod/ap010204.html ]. The violently changing surface [ http://photojournal.jpl.nasa.gov/catalog/PIA02526 ] of Io [ http://antwrp.gsfc.nasa.gov/apod/ap010715.html ] shows not only classic volcano cinder cones [ http://volcanoes.usgs.gov/Products/Pglossary/CinderCone.html ] but also many thrust faults [ http://www.abag.ca.gov/bayarea/eqmaps/supplemt/sld015.htm ] where the ground has fractured and created dramatic shear cliffs [ http://antwrp.gsfc.nasa.gov/apod/ap970218.html ]. The grayscale image [ http://photojournal.jpl.nasa.gov/catalog/PIA03886 ] was taken two years ago by the robot spacecraft Galileo [ http://galileo.jpl.nasa.gov/mission/space-intro.html ] currently orbiting Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap021207.html ]. |
|
North to the Moon's Pole
| Title |
North to the Moon's Pole |
| Explanation |
This image is from the voyage of the intrepid Galileo spacecraft as it passed above the Moon's north pole on its long journey to Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap951206.html ]. It was made over 60 years after Admiral Byrd [ http://www-bprc.mps.ohio-state.edu/ ] became the first to fly over the Earth's north pole [ http://www-bprc.mps.ohio-state.edu/Arctic.html ]. Within a superposed frame of lattitude and longitude lines much of the Moon's familiar face [ http://antwrp.gsfc.nasa.gov/apod/ap950903.html ], dominated by smooth dark mare [ http://antwrp.gsfc.nasa.gov/apod/ap960112.html ], is brightly lit. Near the pole itself, the harsh shadows reveal a rugged, cratered lunarscape [ http://antwrp.gsfc.nasa.gov/apod/ap960420.html ]. |
|
Tonight: A Blue Moon
| Title |
Tonight: A Blue Moon |
| Explanation |
How often does a Full Moon occur twice in a single month? Exactly once in a Blue Moon [ http://oz.sunflower.org/~starwalk/sky_stuff/jul96/july96.html ]. In fact, the modern usage of the term "Blue Moon" [ http://www.nj.com/ofa/aarc.html ] refers to the second Full Moon in a single month. Tonight's Blue Moon [ http://www2.ari.net/home/odenwald/qadir/amoonb.html ] (Universal Time [ http://earthlab.meteor.wisc.edu/el-utc.html ]) will be the first since September 1993. A Blue Moon [ http://pao.gsfc.nasa.gov/gsfc/educ/science/052896.htm ] typically occurs every few years. The reason for the rarity of the Blue Moon [ http://coach4u.com/bluemoon.htm ] is that the 29.53 days between full moons is just slightly shorter than the number of days in the average month. Don't, however, expect the moon to look blue tonight! The term "Blue Moon" is thought to derive from common language expressions used hundreds of years ago. [ http://www.griffithobs.org/IPSBlueMoon.html ] It is possible for the Moon to appear tinged by a blue hue, sometimes caused by fine dirt circulating in the Earth's atmosphere, possibly from a volcanic explosion. The above picture is of our Moon [ http://antwrp.gsfc.nasa.gov/apod/lib/moon.html ] taken was taken in a dark blue morning sky. The bright crescent is the only part directly exposed to sunlight - the rest of the Moon [ http://antwrp.gsfc.nasa.gov/apod/ap951008.html ] glows from sunlight [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ] reflected from the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap951225.html ]. In this dramatic photo [ http://www.icstars.com/HTML/icstars/realfm.htm ], however, the planet Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap951206.html ] is also visible along with its four largest moons [ http://antwrp.gsfc.nasa.gov/apod/ap960710.html ]. |
|
Southwest Mercury
| Title |
Southwest Mercury |
| Explanation |
The planet Mercury resembles a moon. Mercury [ http://www.nineplanets.org/mercury.html ]'s old surface is heavily cratered [ http://liftoff.msfc.nasa.gov/Academy/SPACE/SolarSystem/Meteors/Craters.html ] like many moons. Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap030216.html http://www.solarviews.com/eng/mercury.htm ] is larger than most moons but smaller than Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap990806.html ]'s moon Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap000620.html ] and Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap021104.html ]'s moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap990207.html ]. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap010204.html ] is the only planet more dense. A visitor to Mercury's surface [ http://antwrp.gsfc.nasa.gov/apod/ap960121.html ] would see some strange sights. Because Mercury [ http://www.oulu.fi/~spaceweb/textbook/mercury.html ] rotates exactly three times every two orbits around the Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ], and because Mercury [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mercury.html ]'s orbit is so elliptical, a visitor to Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap010819.html ] might see the Sun [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/interv.html ] rise, stop in the sky, go back toward the rising horizon [ http://antwrp.gsfc.nasa.gov/apod/ap000320.html ], stop again, and then set quickly over the other horizon [ http://antwrp.gsfc.nasa.gov/apod/ap011209.html ]. From Earth, Mercury's proximity to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ] causes it to be visible only for a short time just after sunset or just before sunrise. |
|
Europa's Surface
| Title |
Europa's Surface |
| Explanation |
Voyager spacecraft [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-voyager.html ] images of Europa's surface [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/europa.html ], like the one above, are suggestive of sea ice on Earth [ http://antwrp.gsfc.nasa.gov/apod/ap951118.html ]. The criss-crossing dark streaks may indeed be cracks in its ice-covered surface caused by Jupiter's tidal stresses accompanied by the freezing and expansion of an underlying layer of water [ http://antwrp.gsfc.nasa.gov/apod/ap960806.html ]. This tantalizing prospect of oceans of liquid water [ http://antwrp.gsfc.nasa.gov/apod/ap950905.html ] beneath its frozen surface has helped make the smallest of the Galilean [ http://galileo.imss.firenze.it/museo/4/index.html ] moon's of Jupiter a planned focus of the Galileo spacecraft's ongoing mission to explore the Jovian system. New Europa images and results [ http://newproducts.jpl.nasa.gov/galileo/index.html ] from the Galileo mission were released today revealing [ ftp://ftp.hq.nasa.gov/pub/pao/pressrel/1996/96-164.txt ] details which further suggest that Europa's icy surface was once - and may still be - supported on slush or liquid water. |
|
Europa: Oceans of Life?
| Title |
Europa: Oceans of Life? |
| Explanation |
Is there life beneath Europa's frozen surface? Some believe the oceans found there of carbon-enriched water are the best chance for life [ http://www.etext.org/Zines/Quanta/life.html ], outside the Earth [ http://ucmp1.berkeley.edu/alllife/threedomains.html ], in our Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ]. Europa [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/europa.html ], the fourth largest moon of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950714.html ], was recently discovered [ http://www.stsci.edu/pubinfo/press-releases/95-12.txt ] to have a thin oxygen atmosphere by scientists using the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ]. Although Earth's atmospheric [ http://www.aspire.cs.uah.edu/~jonesj/r.html ] abundance of oxygen is indicative of life [ http://www.gtri.gatech.edu/rh-win96/oxygen.htm ], astronomers speculate that Europa's oxygen arises purely from physical processes. But what an interesting coincidence! The above picture was taken by a Voyager spacecraft [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-voyager.html ] in 1979, but the spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/index.html ] is currently circling Jupiter [ http://antwrp.gsfc.nasa.gov/apod/lib/jupiter.html ] and has been photographing [ http://www.jpl.nasa.gov/galileo/countdown/g1time.html ] Europa [ http://bang.lanl.gov/solarsys/europa.htm ]. The first of these pictures will be released two days from today. Will they show the unexpected? [ http://www.vsc.washington.edu/academic/499/Resources/europa.html ] |
|
Galileo Explores Europa
| Title |
Galileo Explores Europa |
| Explanation |
Details of the crazed cracks [ http://newproducts.jpl.nasa.gov/galileo/ganymede/p47183.html ] criss-crossing Europa's frozen surface [ http://antwrp.gsfc.nasa.gov/apod/ap960813.html ] are apparent in this mosaic of the Galileo spacecraft's latest images [ http://newproducts.jpl.nasa.gov/galileo/index.html ] of Jupiter's ice-covered moon. Curious white stripes, also seen by Voyager [ http://antwrp.gsfc.nasa.gov/apod/ap950905.html ], are clearly visible marking the center of the wide dark fractures. One theory suggests that "dirty geysers" erupting along the cracks deposited darker material followed by a flow of cleaner water ice which produced the stripe. The above image [ ftp://ftp.hq.nasa.gov/pub/pao/pressrel/1996/96-164.txt ] also shows an impact crater about 18.5 miles in diameter surrounded by white ejecta (lower left) and a curving x-pattern at bottom left which suggests fractures between icy plates filled with slush frozen in place. " Is there now or was there ever liquid water [ http://antwrp.gsfc.nasa.gov/apod/ap951118.html ] beneath Europa's surface [ http://antwrp.gsfc.nasa.gov/apod/ap960806.html ]? " These latest results still hold out that possibility -- and so the possibility of life. Europa, along with Mars [ http://antwrp.gsfc.nasa.gov/apod/ap960808.html ] and Saturn's moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap960716.html ] is considered to be one of the few places in our Solar System, beyond [ http://antwrp.gsfc.nasa.gov/apod/ap960701.html ] Earth, where primitive life forms could have developed. Galileo's close flyby of this tantalizing moon is scheduled for December [ http://newproducts.jpl.nasa.gov/galileo/background.html ] of this year. |
|
When Moons and Shadows Dance
| Title |
When Moons and Shadows Dance |
| Explanation |
It's no wonder Jupiter is [ http://galileo.jpl.nasa.gov/jupiter/ jupiter.html ] a favorite target for [ http://www.lpl.arizona.edu/~rhill/alpo/jup.html ] even modest earthbound telescopes. The most massive planet in the solar system [ http://www.seds.org/nineplanets/ nineplanets/datamax.html ] with four of the largest moons also boasts the famous Great Red Spot [ http://csep10.phys.utk.edu/astr161/lect/jupiter/ redspot.html ], a giant hurricane-like storm system over three hundred years old. Recorded on December 15, 2002 between 7:19 and 8:40 UT, over a thousand digital images were processed and stacked to create this spectacular 21 frame animation of the Jovian system [ http://antwrp.gsfc.nasa.gov/apod/ap001118.html ]. South is up and as the Great Red Spot tracks across the face of Jupiter, innermost Galilean [ http://www.jpl.nasa.gov/galileo/ganymede/ discovery.html ] moon Io enters the scene at the far right. Io occults (passes in front of) the edge of the more sedately orbiting Ganymede with Io's shadow [ http://antwrp.gsfc.nasa.gov/apod/ap021207.html ] moving quickly across the gas giant's cloud tops, just below the Red Spot. While the moon Callisto is outside the field of view, its large, dark shadow is also visible crossing the Jovian disk at the upper left. Viewed from Earth, the orbits of the Galilean moons presently lie nearly edge-on, offering many chances to observe similar dances of Jupiter's moons [ http://skyandtelescope.com/observing/objects/planets/ article_771_1.asp ]. |
|
Farewell Jupiter
| Title |
Farewell Jupiter |
| Explanation |
Next stop: Saturn. The Cassini spacecraft [ http://saturn.jpl.nasa.gov/spacecraft/ ], launched from Earth [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] in 1997, has now [ http://saturn.jpl.nasa.gov/operations/present-position.cfm ] swung past Jupiter [ http://www.jpl.nasa.gov/jupiterflyby/ ] and should arrive at Saturn [ http://www.nineplanets.org/saturn.html ] in the year 2004. Pictured to the left [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA03451 ] is a parting shot [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] from Cassini in 2001 January that would not have been possible from Earth: Jupiter showing a crescent phase [ http://antwrp.gsfc.nasa.gov/apod/ap010619.html ]. From the Earth and all points sunward of Jupiter [ http://www.nineplanets.org/jupiter.html ], the gas giant will always appear more fully lit than a crescent [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ]. Recent analysis of Jupiter images [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] taken from Cassini bolsters indications that clouds [ http://antwrp.gsfc.nasa.gov/apod/ap970920.html ] well up from below in the dark colored belts, not the light colored zones [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ], as believed previously. After arriving at Saturn, Cassini [ http://www-groups.dcs.st-andrews.ac.uk/~history/Mathematicians/Cassini.html ] will decelerate to orbit [ http://saturn.jpl.nasa.gov/operations/saturn-arrival.cfm ] the ringed world and send a probe [ http://saturn.jpl.nasa.gov/operations/huygens-mission.cfm ] to its enigmatic moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap000820.html ]. |
|
Southwest Mercury
| Title |
Southwest Mercury |
| Explanation |
The planet Mercury resembles a moon. Mercury [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/mercury.html ]'s old surface is heavily cratered [ http://antwrp.gsfc.nasa.gov/apod/ap950924.html ] like many moons. Mercury [ http://bang.lanl.gov/solarsys/mercury.htm ] is larger than most moons but smaller than Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap951013.html ]'s moon Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap950904.html ] and Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap960717.html ]'s moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap950923.html ]. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap960819.html ] is the only planet more dense. A visitor to Mercury's surface [ http://antwrp.gsfc.nasa.gov/apod/ap960121.html ] would see some strange sights. Because Mercury [ http://www.oulu.fi/~spaceweb/textbook/mercury.html ]rotates exactly three times every two orbits around the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ], and because Mercury [ http://nssdc.gsfc.nasa.gov/photo_gallery/PhotoGallery-Mercury.html ]'s orbit is so elliptical, a visitor to Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap960912.html ] might see the Sun [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/interv.html ] rise, stop in the sky, go back toward the rising horizon [ http://antwrp.gsfc.nasa.gov/apod/ap951114.html ], stop again, and then set quickly over the other horizon. From Earth [ http://antwrp.gsfc.nasa.gov/apod/ap951118.html ], Mercury's proximity to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap960727.html ] cause it to be visible only for a short time [ http://www.maths.qmw.ac.uk/~lms/research/skyeye.html#planet ] just after sunset or just before sunrise. |
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Stars and Planets in the Hal
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| Title |
Stars and Planets in the Halo of the Moon |
| Explanation |
Photographed on [ http://www.photon-echoes.com/ ] March 13th from Caledon, Ontario, Canada, a bright Moon was surrounded by this lovely halo. Planet Jupiter and stars Procyon, Castor, and Pollux also appear within the circle of lunar light. Castor [ http://www.pantheon.org/articles/c/castor.html ] and Pollux, twins in Greek Mythology, are appropriately bright stars of the constellation Gemini [ http://www.astronomical.org/constellations/gem.html ] while Procyon [ http://www.astro.wisc.edu/~dolan/constellations/ hr/2943.html ] is the brightest star in Canis Minor [ http://www.astro.uiuc.edu/~kaler/sow/cmi-p.html ]. The circular halo is produced by six-sided ice crystals [ http://meteoros.de/arten/ee01e.htm ] in thin high-altitude clouds, which refract the moonlight and give the halo a characteristic radius of 22 degrees. For persistent skygazers such apparitions [ http://www.sundog.clara.co.uk/atoptics/phenom.htm ] are relatively easy to see when the Moon and Sun illuminate [ http://www.astro.uiuc.edu/~kaler/sow/atm/atm.html ] planet Earth's skies. |
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