|
|
Calderas And Cliffs Near Io'
…
| Title |
Calderas And Cliffs Near Io's South Pole |
| Explanation |
Braving intense radiation [ http://www-spof.gsfc.nasa.gov/Education/Iradbelt.html ] belts [ http://www-spof.gsfc.nasa.gov/Education/wotherms.html ], the Galileo spacecraft once again [ http://galileo.jpl.nasa.gov/news/status/ status000222.html ] flew past the surface of Jupiter's moon Io [ http://sse.jpl.nasa.gov/features/planets/ jupiter/io.html ] (sounds like EYE-oh [ http://spaceplace.jpl.nasa.gov/gll_io_fact.htm ]) on February 22. Combining high resolution black and white images from that flyby with color data recorded last summer has resulted in this dramatic view [ http://photojournal.jpl.nasa.gov/ cgi-bin/PIAGenCatalogPage.pl?PIA02534 ] of a region near the volcanic moon's south pole. An active and alien landscape, the bright white areas are likely due to sulfur dioxide frost and seem to be concentrated near ridges and cliffs. The three ominous black spots, each about 6-12 miles across, are volcanic craters or calderas [ http://volcano.und.nodak.edu/vwdocs/vwlessons/lessons/ Hot_Spot/Hot_Spot10.html ] covered with recent dark lava. A sinuous channel connects the lower left caldera with a yellowish lava flow. Io is small, but its continuous [ http://www-a.jpl.nasa.gov/galileo/ganymede/ 122096.html ] activity is driven by the drastic tides [ http://co-ops.nos.noaa.gov/restles1.html ] induced by Jupiter [ http://sse.jpl.nasa.gov/features/planets/ jupiter/jupiter.html ] and the other Jovian moons. It is estimated that the resulting volcanism [ http://volcano.und.edu/vwdocs/planet_volcano/Io/ Overview.html ] completely resurfaces Io [ http://antwrp.gsfc.nasa.gov/apod/ap970321.html ] every million years. |
|
Jupiter Eyes Ganymede
| Title |
Jupiter Eyes Ganymede |
| Explanation |
Who keeps an eye [ http://ciclops.lpl.arizona.edu/ciclops/ images_jupiter.html ] on the largest moon in the Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ]? This moon, visible on the lower right, is Ganymede [ http://www.seds.org/nineplanets/nineplanets/ganymede.html ], and the planet it orbits, Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ], seems to be keeping a watchful eye, as its Great Red Spot [ http://antwrp.gsfc.nasa.gov/apod/ap960802.html ] appears serendipitously nearby. This recently released [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02837 ] enhanced-contrast image from the robot spacecraft Cassini [ http://www.jpl.nasa.gov/cassini/english/spacecraft/ ] captures new details of the incredible intricacies of Jupiter's complex cloud [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ] patterns. Features as small as 250 kilometers can be seen. Counter-clockwise rotating high-pressure white ovals [ http://antwrp.gsfc.nasa.gov/apod/ap990105.html ] that are similar to the Great Red Spot [ http://antwrp.gsfc.nasa.gov/apod/ap001123.html ] appear in the red band below the spot. Between these spots are darker low-pressure systems [ http://www.usatoday.com/weather/wlowpres.htm ] that rotate clockwise. The hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] and helium [ http://pearl1.lanl.gov/periodic/elements/2.html ] that compose most of Jupiter's clouds is nearly invisible - the trace chemicals that give Jupiter these colors remain unknown [ http://antwrp.gsfc.nasa.gov/apod/ap960803.html ]. The Cassini spacecraft [ http://quest.arc.nasa.gov/saturn/qa/cassini/ ] is using Jupiter [ http://www.hawastsoc.org/solar/eng/jupiter.htm ] to pull it [ http://www.science.nasa.gov/newhome/headlines/ast24jun99_1.htm#gravityassist ] toward Saturn [ http://www.seds.org/nineplanets/nineplanets/saturn.html ], where it is scheduled [ http://www.jpl.nasa.gov/cassini/Mission/cruise.html ] to arrive in 2004. |
|
Jupiter, Europa, and Callist
…
| Title |
Jupiter, Europa, and Callisto |
| Explanation |
As the robot Cassini spacecraft [ http://www.jpl.nasa.gov/cassini/english/spacecraft/ ] rounds Jupiter [ http://www.jpl.nasa.gov/galileo/jupiter/jupiter.html ] on its way toward Saturn [ http://www.seds.org/nineplanets/nineplanets/saturn.html ], it has taken a sequence of images [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] of the gas giant with its four largest moons [ http://antwrp.gsfc.nasa.gov/apod/ap001118.html ]. Previously released images have highlighted Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap001212.html ] and Io [ http://antwrp.gsfc.nasa.gov/apod/ap001226.html ]. Pictured above [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02861 ] are the two remaining Galilean satellites [ http://www.jpl.nasa.gov/galileo/ganymede/discovery.html ]: Europa [ http://www.hawastsoc.org/solar/eng/europa.htm ] and Callisto [ http://cass.jsc.nasa.gov/pub/research/outerp/call.html ]. Europa [ http://www.jpl.nasa.gov/galileo/moons/europa.html ] is the bright moon superposed near Jupiter's Great Red Spot [ http://antwrp.gsfc.nasa.gov/apod/ap001123.html ], while Callisto is the dark moon near the frame edge. Callisto [ http://www.jpl.nasa.gov/galileo/moons/callisto.html ] is so dark that it would be hard to see here if its brightness was not digitally enhanced. Recent evidence indicates [ http://www.jpl.nasa.gov/galileo/news/release/press001216.html ] that both moons hold salt-water seas under surface ice that might be home to extra-terrestrial life. By noting the times that moons disappeared and reappeared behind Jupiter in 1676, Ole Roemer [ http://es.rice.edu/ES/humsoc/Galileo/Catalog/Files/roemer.html ] was able to make the first accurate estimation of the speed of light [ http://www.stats.uwaterloo.ca/~rwoldfor/papers/sci-method/paperrev/node4.html ]. |
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Jupiter, Io, and Shadow
| Title |
Jupiter, Io, and Shadow |
| Explanation |
Just as planets orbit our Sun, Jupiter's Moons [ http://antwrp.gsfc.nasa.gov/apod/ap001118.html ] orbit Jupiter. Pictured above [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02860 ] is the closest of Jupiter's Galilean Satellites [ http://www.jpl.nasa.gov/galileo/ganymede/discovery.html ], Io [ http://www.seds.org/nineplanets/nineplanets/io.html ], superposed in front of the giant planet it circles. To the left of Io [ http://www.hawastsoc.org/solar/eng/edu/moonio.htm ] is a dark spot that is its own shadow. The tremendous complexities that can be seen in Jupiter's banded, swirling atmosphere [ http://antwrp.gsfc.nasa.gov/apod/ap970310.html ] are being studied and may provide insight as to how Earth's atmosphere [ http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html ] behaves. The above true-color contrast-enhanced image [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02860 ] was taken [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] two weeks ago by the robot spacecraft Cassini [ http://quest.arc.nasa.gov/saturn/qa/cassini/ ], currently passing Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ] and on its way to Saturn [ http://antwrp.gsfc.nasa.gov/apod/saturn.html ] in 2004. Engineers continue to study [ http://www.jpl.nasa.gov/jupiterflyby/news/mission_status.html ] the Cassini spacecraft [ http://www.jpl.nasa.gov/basics/cassini.htm ] itself to understand why it required more force than normal to turn one of its maneuvering wheels. |
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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. |
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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 |
|
Earth's Moon, A Familiar Fac
…
| Title |
Earth's Moon, A Familiar Face |
| Explanation |
The above mosaic of the Earth's Moon [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/luna.html ] was compiled from photos taken by the spacecraft Clementine [ http://nssdc.gsfc.nasa.gov/planetary/clementine.html ] in 1994. This image represents the side of the Moon familiar to Earth dwellers. The Moon [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/moon.html ] revolves around the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ] about once every 28 days. Since its rate of rotation about its axis is also once in 28 days, it always keeps the same face toward the Earth. As the Moon travels around its orbit, the Earth based view of the half of the Moon [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-moon.html ] that faces the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ] changes causing the regular monthly progression of Lunar phases. Humans first crashed a spacecraft [ http://nssdc.gsfc.nasa.gov/cgi-bin/database/www-nmc?59-014A ] into the Moon in 1959, but the first humans to reach the Moon landed [ http://www.ksc.nasa.gov/history/apollo/apollo-11/apollo-11.html ] in 1969. There are now golf balls [ http://ees5-www.lanl.gov/APOLLO/a14.clsout2.html ] on the Moon. Tomorrow's picture: Ganymede: Moonquake World |
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Callisto: Dark Smashed Iceba
…
| Title |
Callisto: Dark Smashed Iceball |
| Explanation |
Callisto [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/callisto.html ] is a dirty battered world, showing the most beaten surface of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950625.html ]'s major moons. Made of a rocky core covered by fractured ice, Callisto [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/callisto.html ]'s past collisions with large meteors are evident as large craters surrounded by concentric rings. The four largest moons of Jupiter: Io [ http://antwrp.gsfc.nasa.gov/apod/ap950803.html ], Europa [ http://antwrp.gsfc.nasa.gov/apod/ap950905.html ], Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap950904.html ], and Callisto were all 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 with early telescopes and are now known as the Galilean satellites. The NASA spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/ ] is scheduled to arrive at Jupiter is December of 1995. Tomorrow's picture: Distant Galaxies |
|
Jupiter's Moon Amalthea
| Title |
Jupiter's Moon Amalthea |
| Explanation |
Amalthea is Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap951013.html ]'s fifth largest moon, much smaller than the four Galilean [ http://bang.lanl.gov/video/stv/arshtml/arstoc.html ] satellites Io [ http://antwrp.gsfc.nasa.gov/apod/ap950803.html ], Europa [ http://antwrp.gsfc.nasa.gov/apod/ap950905.html ], Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap950904.html ], and Callisto [ http://antwrp.gsfc.nasa.gov/apod/ap950906.html ]. The orbit of Amalthea [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/amalthea.html#amalthea ] is inside of these moons, and with its long axis always pointing toward Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950625.html ]. It's dark surface color is probably due to sulfur being expelled from Io [ http://antwrp.gsfc.nasa.gov/apod/ap950804.html ]. Amalthea is not massive enough for its internal gravity to make it spherical. Amalthea [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/amalthea.html ] was discovered in 1892 by Edward Barnard. |
|
Jupiter, Io, and Ganymede's
…
| Title |
Jupiter, Io, and Ganymede's Shadow |
| Explanation |
Jupiter [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/jupiter.html ], the solar system [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ]'s largest planet, is seen here next to Io [ http://antwrp.gsfc.nasa.gov/apod/ap950803.html ], its closest Galilean [ http://bang.lanl.gov/video/stv/arshtml/arstoc.html ] moon. On the cloud tops of Jupiter [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/jupiter.html ] near the left edge of the picture can be seen a dark circular spot which is caused by the shadow of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950625.html ]'s largest moon Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap950904.html ]. Jupiter [ http://nssdc.gsfc.nasa.gov/photo_gallery/PhotoGallery-Jupiter.html ]'s cloud tops show light bands and dark belts. The clouds are primarily composed of hydrogen [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ] and helium [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#helium ], but their intense colors are probably caused by very small amounts of heavier elements such as sulfur or organic (carbon-containing) compounds. |
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Saturn's Cleanest Moon: Ence
…
| Title |
Saturn's Cleanest Moon: Enceladus |
| Explanation |
Enceladus [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/enceladus.html ] orbits Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap951018.html ] between the smaller Mimas [ http://antwrp.gsfc.nasa.gov/apod/ap950924.html ] and the larger Tethys [ http://antwrp.gsfc.nasa.gov/apod/ap951124.html ]. Enceladus is composed mostly of water ice and has the cleanest and purest ice surface in the Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ]. It's surface therefore appears nearly white. The surface also has many unusual groves and relatively few craters, like Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap951013.html ]'s moon Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap950904.html ]. This indicates that the surface is young and/or newly reformed. To explain this, some astronomers speculate that Enceladus [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/enceladus.html ] is susceptible to some sort of volcanic [ http://antwrp.gsfc.nasa.gov/apod/ap950804.html ] activity. Enceladus was originally discovered in 1789 by William Herschel [ http://star.arm.ac.uk/history/herschel.html ]. |
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Uranus' Moon Miranda
| Title |
Uranus' Moon Miranda |
| Explanation |
NASA's robot spacecraft Voyager 2 passed the planet Uranus [ http://antwrp.gsfc.nasa.gov/apod/ap950816.html ] and its moons in 1986. While the cloud tops of Uranus [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/uranus.html ] proved to be rather featureless, the surface of Miranda [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/miranda.html ], the innermost of Uranus [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/uranus.html ]' large moons, showed several interesting features. Voyager 2 passed closer to Miranda [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/miranda.html ] than to any Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ] body and hence photographed it with the clearest resolution. Miranda's heavily cratered terrain shows grooves like Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap951208.html ]'s moon Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap950904.html ] and several valleys and cliffs. Miranda is made of a roughly equal mix of ice and rock. Miranda was discovered by Gerard Kuiper in 1948. |
|
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. |
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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. |
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Galileo Photographs Ganymede
| Title |
Galileo Photographs Ganymede |
| Explanation |
Ganymede's surface is slowly being pulled apart. This photo of Ganymede [ http://antwrp.gsfc.nasa.gov/apod/lib/gany01_gal.txt ] was released earlier today [ http://newproducts.jpl.nasa.gov/galileo/ganymede/g1images.html ] by the Galileo team at NASA. The Galileo Spacecraft [ http://newproducts.jpl.nasa.gov/galileo/scpics.html ] arrived at Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950625.html ] in December 1995. In late June, the spacecraft passed within 10,000 kilometers of Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap950904.html ]'s icy surface, and took pictures showing complex surface details for the first time. The line-like features in this photo are sunlit ridges rising above Ganymede [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ganymede.html ]'s ice-plains. The circular features are impact craters. Ganymede [ http://bang.lanl.gov/solarsys/ganymede.htm ] is the largest moon of Jupiter [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/jupiter.html ] and hence the largest of the four Galilean satellites: Io [ http://antwrp.gsfc.nasa.gov/apod/ap950803.html ], Europa [ http://antwrp.gsfc.nasa.gov/apod/ap950905.html ], Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap960627.html ], and Callisto [ http://antwrp.gsfc.nasa.gov/apod/ap950906.html ]. |
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Galileo, Cassini, and the Gr
…
| Title |
Galileo, Cassini, and the Great Red Spot |
| Explanation |
Imagine a hurricane that lasted for 300 years! Jupiter's Great Red Spot indeed seems to be a giant hurricane-like storm system [ http://www.coaps.fsu.edu/~meyers/fig/vortex.html ] rotating with the Jovian clouds. Observed in 1655 by Italian-French astronomer Jean-Dominique Cassini [ http://www.jpl.nasa.gov/cassini/MoreInfo/casshuyg.html ] it is seen here over 300 years later - still going strong - in a mosaic of recent Galileo spacecraft images [ http://www.jpl.nasa.gov/galileo/ganymede/073196.html ]. The Great Red Spot is a cold, high pressure area 2-3 times wider than planet Earth. Its outer edge rotates in a counter clockwise direction [ http://bang.lanl.gov/solarsys/raw/jup/jupiter3.avi ] about once every six days. Jupiter's own [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/jupiter.html ] rapid rotation period [ http://www.kalmbach.com/astro/Bytes/JUPITER.html ] is a brief 10 hours. The Solar System's largest gas giant planet [ http://antwrp.gsfc.nasa.gov/apod/lib/jupiter.html ], it is presently well placed [ http://antwrp.gsfc.nasa.gov/apod/ap960723.html ] for evening viewing [ http://www.kalmbach.com/astro/Backyard/Jupiter.html ]. (APOD thanks to Alan Radecki for assembling a preliminary mosaic from the Galileo imagery!) |
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Galileo Zooms in on Jupiter'
…
| Title |
Galileo Zooms in on Jupiter's Red Spot |
| Explanation |
What does the largest storm system ever recorded look like close-up? This storm system is Jupiter [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/jupiter.html ]'s Great Red Spot [ http://antwrp.gsfc.nasa.gov/apod/ap960802.html ] and it was captured recently [ http://newproducts.jpl.nasa.gov/galileo/ganymede/082296.html ] in detail by the robot spacecraft Galileo [ http://antwrp.gsfc.nasa.gov/apod/ap951206.html ] now in orbit around Jupiter [ http://antwrp.gsfc.nasa.gov/apod/lib/jupiter.html ]. Using real images from three color filters, the Galileo team was able to compute what a person would see if able to float just above this ancient rotating cloud system [ http://irtf.ifa.hawaii.edu/GalleryOfImages/grs5ch95a.html ]. But don't get too close - remember that Jupiter's Great Red Spot [ http://tnj.phys.tue.nl/Intro/redspot.html ] is a cold, high pressure area more than twice as wide as planet Earth [ http://antwrp.gsfc.nasa.gov/apod/ap960819.html ]. |
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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 ]. |
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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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Impact On Europa
| Title |
Impact On Europa |
| Explanation |
This bull's-eye pattern marks the impact of a mountain-sized comet or asteroid [ http://antwrp.gsfc.nasa.gov/apod/ap960604.html ] on the icy surface of Jupiter's moon Europa [ http://antwrp.gsfc.nasa.gov/apod/ap961120.html ]. Recorded by the Galileo spacecraft [ http://galileo.ivv.nasa.gov/gem/ ] in April of this year, the composite false color image [ http://galileo.ivv.nasa.gov/ganymede/p48954.html ] clearly reveals the telltale concentric fractures [ http://antwrp.gsfc.nasa.gov/apod/ap960112.html ] which cover about 86 miles - roughly equivalent to the Island of Hawaii [ http://antwrp.gsfc.nasa.gov/apod/ap970302.html ]. The fat reddish and finer blue-green lines overlay the impact fractures and must therefore be younger surface features [ http://antwrp.gsfc.nasa.gov/apod/ap970410.html ] formed after the impact. The dark red color may be the result of a a relatively dirty water-ice mixture. The possibility of liquid water below the ice has fueled speculation that life may exist [ http://www.etext.org/Zines/Quanta/life.html ] on this large and distant moon [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/europa.html ]. |
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Jupiter And Family
| Title |
Jupiter And Family |
| Explanation |
This composite image [ http://galileo.ivv.nasa.gov/ganymede/052997.html ] features classic portraits of members of one of the Solar System's [ http://antwrp.gsfc.nasa.gov/apod/ap961214.html ] most prominent families - Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap970920.html ] and its four large "Galilean" [ http://antwrp.gsfc.nasa.gov/apod/ap960830.html ] moons. Starting from the top the moons are Io [ http://antwrp.gsfc.nasa.gov/apod/ap970321.html ], Europa [ http://antwrp.gsfc.nasa.gov/apod/ap970117.html ], Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap961107.html ], and Callisto [ http://antwrp.gsfc.nasa.gov/apod/ap961209.html ]. The top-to-bottom order is also the order of increasing distance from Jupiter. These are big moons indeed which attend the largest planet [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/jupiter.html ]. The smallest of the lot, Europa, is the size of Earth's moon [ http://antwrp.gsfc.nasa.gov/apod/ap970924.html ] while Ganymede is the largest moon in the Solar System. In fact, Ganymede with a diameter of 3,100 miles, is larger than the planets Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap961217.html ] and Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap960311.html ]. The swirling Great Red Spot [ http://antwrp.gsfc.nasa.gov/apod/ap960827.html ] appears at the edge of Jupiter. A hurricane-like storm system that has persisted for over 300 years, two to three earths could fit inside it. Battered Callisto's [ http://antwrp.gsfc.nasa.gov/apod/ap950906.html ] image was recorded during the 1979 flyby of Voyager [ http://antwrp.gsfc.nasa.gov/apod/ap960629.html ]. The other portraits were taken by the Galileo spacecraft [ http://galileo.ivv.nasa.gov/spacecraft.html ] which began exploring the Jovian system in 1995. |
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A Triple Eclipse on Jupiter
| Title |
A Triple Eclipse on Jupiter |
| Explanation |
Part of Jupiter is missing. Actually, three parts appear to be missing. In reality though, the three dark spots seen in the above photograph [ http://www.opi.arizona.edu/newsrel/science/jan98/3moons.htm ] are only shadows. The unusual alignment of three of Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ]'s moons between the Jovian giant [ http://bang.lanl.gov/solarsys/jupiter.htm ] and the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap960518.html ] was imaged last November 10th. The shadows of Io [ http://antwrp.gsfc.nasa.gov/apod/ap971110.html ], Callisto [ http://antwrp.gsfc.nasa.gov/apod/ap950906.html ], and Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap961107.html ] move across Jupiter as these moons progress in their orbits. It was by noting the times of eclipse of Jupiter's moons in 1675 that Ole Roemer [ http://es.rice.edu/ES/humsoc/Galileo/Catalog/Files/roemer.html ] became the first person to measure [ http://www.pd.astro.it/~v_astro/ESO/astronomyonline/market/experiments/advanced/skills302.html ] the speed of light [ http://www.best.com/~dolphin/chistory.html ]. When a shadow from Earth's Moon [ http://antwrp.gsfc.nasa.gov/apod/ap980108.html ] crosses the Earth's surface, the people inside the shadow see an eclipse [ http://antwrp.gsfc.nasa.gov/apod/ap951024.html ] of the Sun. |
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Pastel Planet, Triple Eclips
…
| Title |
Pastel Planet, Triple Eclipse |
| Explanation |
This false-color [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2004/30/ ] image of banded gas giant Jupiter shows a triple eclipse in progress on March 28 - a relatively rare [ http://antwrp.gsfc.nasa.gov/apod/ap980202.html ] event, even for a large planet with [ http://antwrp.gsfc.nasa.gov/apod/ap001118.html ] many moons. Captured by the Hubble Space Telescope's near-infrared camera are shadows of [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2004/30/image/b ] Jupiter's moons Ganymede (left edge), Callisto (right edge) and Io, three black spots crossing the sunlit Jovian cloud tops. In fact, Io itself [ http://antwrp.gsfc.nasa.gov/apod/ap020706.html ] is visible as [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2004/30/image/c ] a white spot near picture center with a bluish Ganymede above and to the right, but Callisto is off the right hand edge of the scene. Viewed from Jupiter's perspective, these shadow crossings [ http://antwrp.gsfc.nasa.gov/apod/ap030227.html ] would be seen as solar eclipses, analogous to the Moon's shadow [ http://antwrp.gsfc.nasa.gov/apod/ap040926.html ] crossing the sunlit face of planet Earth. Historically [ http://www.what-is-the-speed-of-light.com/ early-thoughts-speed-of-light.html ], timing the eclipses of Jupiter's moons allowed astronomer Ole Roemer [ http://www.college-optometrists.org/college/ museum/observatory/roemer.htm ] to make the first accurate measurement [ http://www.what-is-the-speed-of-light.com/ roemer-speed-of-light.html ] of the speed of light in 1676. |
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Io Aurora
| Title |
Io Aurora |
| Explanation |
Alluring aurora surrounding Io [ http://photojournal.jpl.nasa.gov/ cgi-bin/PIAGenCatalogPage.pl?PIA01637 ] (eye-oh) appear as a ghostly glow while the volcanic moon orbits [ http://antwrp.gsfc.nasa.gov/apod/ap970623.html ] within Jupiter's dark shadow. Gas giant Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] is off to the right of this image, recorded in May by the robot Galileo spacecraft's solid state imaging camera [ http://www.jpl.nasa.gov/galileo/sepo/ ] from a distance of about 1.3 million kilometers. Energetic charged particles colliding with Io's atmospheric gases create the vivid colors and produce the red and green glow analogous to the aurora of Earth [ http://antwrp.gsfc.nasa.gov/apod/ap970402.html ]. The striking blue light is caused by dense volcanic plumes [ http://www-a.jpl.nasa.gov/galileo/ganymede/122096.html ] and may indicate regions electrically connected to Jupiter itself [ http://antwrp.gsfc.nasa.gov/apod/ap980123.html ]. |
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