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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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Zal Patera on Jupiter's Moon
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| Title |
Zal Patera on Jupiter's Moon Io |
| Explanation |
The Galileo orbiter [ http://www.jpl.nasa.gov/galileo/mission.html ]'s flyby of Io [ http://www.seds.org/nineplanets/nineplanets/io.html ] last November captured an unusual part of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ]'s volcanic moon. From 26,000 kilometers away, Zal Patera [ http://wwwflag.wr.usgs.gov/USGSFlag/Space/nomen/append5.html ] was found to be a cauldron of flowing lava [ http://antwrp.gsfc.nasa.gov/apod/ap991220.html ], gaseous vents [ http://antwrp.gsfc.nasa.gov/apod/ap970428.html ], and tremendous peaks [ http://antwrp.gsfc.nasa.gov/apod/ap960805.html ]. Red lava can be seen in the above picture [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02527 ] erupting along the base of the volcanic caldera, while cooling black lava lines the edge of a volcanic plateau. Shadow lengths indicate that the top of Zal Patera [ http://antwrp.gsfc.nasa.gov/apod/ap990513.html ] towers nearly 5 kilometers over Io [ http://galileo.jpl.nasa.gov/moons/io.html ]'s molten surface. Galileo zoomed past Io again last month [ http://galileo.jpl.nasa.gov/news/status/status000225.html ], and has begun beaming back images taken only 200 kilometers over Io's surface [ http://antwrp.gsfc.nasa.gov/apod/ap990920.html ]. |
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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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Europa: Ice Line
| Title |
Europa: Ice Line |
| Explanation |
This bright white swath cutting across the surface of icy Jovian moon Europa [ http://galileo.jpl.nasa.gov/moons/europa.html ] is known as Agenor Linea [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA00877 ]. In all about 1000 kilometers long and 5 kilometers wide, only a section is pictured here [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA01647 ] as part of a combined color and black and white image based on data from the Galileo spacecraft. Most linear features on Europa [ http://www.jpl.nasa.gov:80/galileo/europa/fact.html ] are dark in color but Agenor Linea is uniquely bright for unknown reasons. Also unknown is the origin of the reddish material along the sides. While these and other details of Europa's [ http://www.jpl.nasa.gov:80/galileo/news8.html ] surface formations remain mysterious, the general results of Galileo's exploration of Europa have supported the idea that an ocean of liquid water lies beneath [ http://photojournal.jpl.nasa.gov/ cgi-bin/PIAGenCatalogPage.pl?PIA01669 ] the cracked and frozen crust. An extraterrestrial liquid ocean [ http://science.nasa.gov/newhome/headlines/ast05mar98_1.htm ] holds out the tantalizing possibility [ http://quest.arc.nasa.gov/galileo/features/life.html ] of life. |
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Planets Above The Clouds
| Title |
Planets Above The Clouds |
| Explanation |
Clouds scatter the faint orange rays of the setting sun [ http://antwrp.gsfc.nasa.gov/apod/ap000115.html ] in the foreground of this breathtaking photograph from the summit [ http://www.ifa.hawaii.edu/mko/mko.html ] of Mauna Kea, Hawaii [ http://antwrp.gsfc.nasa.gov/apod/ap980725.html ]. Taken on April 7th, this skyscape features a dramatic lunar and planetary alignment [ http://antwrp.gsfc.nasa.gov/apod/ap000406.html ]. An overexposed crescent moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ] dominates the celestial scene, but the bright "star" just below and to its right is Saturn [ http://www.jpl.nasa.gov/cassini/Kids/stories/ ] while further below Saturn is a close pairing of brilliant Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ] and a fainter, yellowish Mars [ http://marsnt3.jpl.nasa.gov/education/students.html ]. Red giant star Aldebaran [ http://www.bo.astro.it/copernic/alde-eng.html ] is almost directly above the moon near the top of the image and the bright blue stars of the Pleiades cluster [ http://www.aao.gov.au/images.html/captions/uks018.html ] are visible about midway up and to the right of the moon-Aldebaran line. The good news is that planetary alignments [ http://www.skypub.com/news/special/whypanic.html ] like this one do not portend [ http://tech-two.mit.edu/Shakespeare/Tragedy/macbeth/ macbeth.html ] disasters, are relatively common, and can clearly make inspirational viewing for casual stargazers and astronomers alike. The bad [ http://www.badastronomy.com/bad/misc/planets.html ] news is that the world is not going to end because of the highly publicized planetary alignment [ http://www.griffithobs.org/SkyAlignments.html ] occurring tomorrow, May 5th -- so you probably will have to go to work [ http://www.nasa.gov/newsinfo/alignment.html ]! |
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Calderas And Cliffs Near Io'
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| 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. |
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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 Halo Around the Moon
| Title |
A Halo Around the Moon |
| Explanation |
Have you ever seen a halo around the Moon? This fairly common sight occurs when high thin clouds [ http://ww2010.atmos.uiuc.edu/(Gh)/wwhlpr/cirrus.rxml?hret=/guides/mtr/opt/ice/halo/22.rxml ] containing millions of tiny ice crystals [ http://dspace.dial.pipex.com/lc/halo/crystals.htm ] cover much of the sky. Each ice crystal [ http://kristall.uni-mki.gwdg.de/homep1.htm ] acts like a miniature lens. Because most [ http://dspace.dial.pipex.com/lc/halo/xtalreal.htm ] of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees, which corresponds to the radius of the Moon Halo [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/halo/22.rxml ]. A similar Sun Halo [ http://antwrp.gsfc.nasa.gov/apod/ap990823.html ] may be visible during the day. The town in the foreground of the above picture [ http://www.skylook.net/album/fenatm/fat3i.htm ] is San Sebastian [ http://www.donsnsn.es/icaste.htm ], Spain [ http://www.odci.gov/cia/publications/factbook/sp.html ]. The distant planet Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ] appears by chance on the halo [ http://dspace.dial.pipex.com/lc/halo/halfeat.htm ]'s upper right. Exactly how ice-crystals form [ http://www.public.iastate.edu/~skrentz/ice_crystal.htm ] in clouds remains under investigation [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995dri..rept.....H ]. |
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Ganymede: The Largest Moon i
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| Title |
Ganymede: The Largest Moon in the Solar System |
| Explanation |
If Ganymede orbited the Sun, it would be considered a planet. The reason is that Jupiter [ http://galileo.jpl.nasa.gov/jupiter/jupiter.html ]'s moon Ganymede [ http://www.seds.org/nineplanets/nineplanets/ganymede.html ] is not only the largest moon in the Solar System [ http://www.seds.org/nineplanets/nineplanets/datamax.html ], it is larger than planets Mercury [ http://www.seds.org/nineplanets/nineplanets/mercury.html ] and Pluto [ http://dosxx.colorado.edu/plutohome.html ]. The robot spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/overview.html ] currently orbiting Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] has been able to zoom by Ganymede [ http://www.solarviews.com/eng/ganymede.htm ] several times and snap many close-up pictures. Ganymede, shown above [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA00716 ] in its natural colors, sports a large oval dark region known as Galileo Regio [ http://www.jpl.nasa.gov/galileo/ganymede/121896.html ]. In general, the dark regions on Ganymede [ http://sse.jpl.nasa.gov/features/planets/jupiter/ganymede.html ] are heavily cratered, implying they are very old, while the light regions are younger and dominated by unusual grooves [ http://antwrp.gsfc.nasa.gov/apod/ap960711.html ]. The origin of the grooves is still under investigation [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998Icar..135..317P ]. |
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Up Close to Jupiter's Moon I
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| Title |
Up Close to Jupiter's Moon Io |
| Explanation |
Above is the highest resolution photograph [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02556 ] yet taken of the Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ]'s strangest moon. The surface of Jupiter [ http://www.solarviews.com/eng/jupiter.htm ]'s moon Io [ http://galileo.jpl.nasa.gov/moons/io.html ] is home to violent volcanoes [ http://antwrp.gsfc.nasa.gov/apod/ap000606.html ] that are so active they turn the entire moon inside out. The above photograph [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02556 ] shows a region four kilometers across and resolves features only five meters [ http://www.twenj.com/measures.htm ] across. Many revealed details are not well understood. In general, the bright areas are higher terrain than the darker areas, but some areas of the surface appear eroded [ http://www.qub.ac.uk/geosci/teaching/postgrad/workshop1/erosion1.html ] by an unknown process. Although the parts of Io's surface [ http://antwrp.gsfc.nasa.gov/apod/ap970321.html ] near erupting volcanoes are hot enough to melt rock, most of Io [ http://antwrp.gsfc.nasa.gov/apod/ap990920.html ] has cooled well below the freezing point of water [ http://www.nyu.edu/pages/mathmol/modules/water/info_water.html ]. The robot spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/overview.html ] during its most recent flyby [ http://galileo.jpl.nasa.gov/news/release/press000531.html ] of Io [ http://www.seds.org/nineplanets/nineplanets/io.html ] took the above image in 2000 February. |
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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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Moon And Venus Share The Sky
| Title |
Moon And Venus Share The Sky |
| Explanation |
July is drawing to a close and in the past few days, some early morning risers [ http://antwrp.gsfc.nasa.gov/apod/ap990714.html ] could have looked east and seen a crescent Moon sharing the pre-dawn [ http://science.nasa.gov/headlines/y2000/ast25jul_1m.htm ] skies with planets Jupiter and Saturn. Planet Mercury will also pass about 2 degrees from the thin waning crescent Moon [ http://aa.usno.navy.mil/AA/faq/docs/moon_phases.html ] just before sunrise near the eastern horizon on Saturday, July 29. And finally, on the evening of July 31st, Venus will take its turn near the crescent Moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ]. But this time it will be a day-old crescent Moon near the western horizon, shortly after sunset [ http://antwrp.gsfc.nasa.gov/apod/ap000507.html ]. In fact [ http://pages.prodigy.net/pam.orman/JoeAlmanac2000.html ], on July 31 (August 1 Universal Time) the Moon will occult [ http://www.skypub.com/sights/occultations/lunar/ 0001lunarocc.html ] (pass in front of) Venus for northwestern observers [ http://www.skypub.com/sights/images2000/ 0008moonvenus_big.jpg ] in North America. This telescopic picture taken on 31 December 1997, shows a lovely young crescent Moon and brilliant crescent Venus in [ http://antwrp.gsfc.nasa.gov/apod/ap990903.html ] the early evening sky near Bursa, Turkey [ http://www.mersina.com/Turkey/Marmara/Bursa/index.html ]. And what about the Sun? On Sunday, July 30, a partial eclipse of the Sun [ http://sunearth.gsfc.nasa.gov/eclipse/extra/ PSE2000Jul31.html ] will be visible from some locations [ http://sunearth.gsfc.nasa.gov/eclipse/OH/ PSE2000Jul.gif ] in North America. |
|
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. |
|
Approaching Jupiter
| Title |
Approaching Jupiter |
| Explanation |
In 1979 the Voyager 1 spacecraft [ http://vraptor.jpl.nasa.gov/voyager/voyager_fs.html ] compiled this view as it approached the gas giant Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ]. Snapping a picture every time the Great Red Spot [ http://antwrp.gsfc.nasa.gov/apod/ap960827.html ] was properly aligned, the above time-lapse sequence [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02259 ] shows not only spot [ http://www.gfdl.gov/~gw/ ] rotation but also the swirling of neighboring clouds [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ]. Since Jupiter [ http://www.solarviews.com/eng/jupiter.htm ] takes about 10 hours to rotate, this short sequence actually covers several days. Voyager 1 shot past Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ] rapidly taking pictures on which many discoveries [ http://www.solarviews.com/eng/vgrjup.htm ] would be made, including previously unknown cloud patterns [ http://antwrp.gsfc.nasa.gov/apod/ap970920.html ], rings [ http://antwrp.gsfc.nasa.gov/apod/ap980916.html ], moons [ http://www.seds.org/nineplanets/nineplanets/amalthea.html#adrastea ], and active volcanoes [ http://antwrp.gsfc.nasa.gov/apod/ap960805.html ] on Jupiter's moon Io [ http://www.jpl.nasa.gov/galileo/moons/io.html ]. Voyager is moving so fast that it will one day leave [ http://antwrp.gsfc.nasa.gov/apod/ap980620.html ] our Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ]. |
|
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 ]. |
|
Io Rotating
| Title |
Io Rotating |
| Explanation |
The surface of Io is continually changing. Jupiter's moon [ http://antwrp.gsfc.nasa.gov/apod/ap990920.html ] is the home to many powerful volcanoes [ http://antwrp.gsfc.nasa.gov/apod/ap991126.html ] so active they are effectively turning the moon inside out. The above time-lapse sequence [ http://solarviews.com/cap/jup/vio1.htm ] is a composite of images taken during two space missions that approached the violent moon: Voyager [ http://vraptor.jpl.nasa.gov/voyager/voyager_fs.html ] and Galileo [ http://www.jpl.nasa.gov/galileo/mission.html ]. The sequence shows Io [ http://www.seds.org/nineplanets/nineplanets/io.html ] during a complete rotation, which corresponds to a complete revolution around Jupiter [ http://www.jpl.nasa.gov/galileo/Jovian.html ] since Io [ http://cass.jsc.nasa.gov/pub/research/outerp/io.html ] always keeps the same face toward the giant planet. The rampant volcanism is thought to be caused by Jupiter's more distant Galilean Moons [ http://solarviews.com/eng/galdisc.htm ] (Europa [ http://www.seds.org/nineplanets/nineplanets/europa.html ], Ganymede [ http://www.seds.org/nineplanets/nineplanets/ganymede.html ], and Callisto [ http://www.seds.org/nineplanets/nineplanets/callisto.html ]) pulling on Io and continually distorting its shape, causing internal frictional [ http://www.cord.edu/dept/physics/p128/lecture99_12.html ] heating. Io is composed mostly of rock, with the yellow color originating from sulfur [ http://chemlab.pc.maricopa.edu/periodic/S.html ]. The causes of many of the other colors remain a topic of research [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999Icar..140..265G ]. |
|
Cassini Spacecraft Approache
…
| Title |
Cassini Spacecraft Approaches Jupiter |
| Explanation |
A new spacecraft has entered the outer Solar System: Cassini [ http://www.jpl.nasa.gov/cassini/english/spacecraft/ ]. Launched in 1997 [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] and bound for Saturn in 2004, Cassini sent back the above image [ http://ciclops.lpl.arizona.edu/ciclops/Images_jupiter.html ] last week while approaching the giant planet Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ]. Cassini [ http://quest.arc.nasa.gov/saturn/qa/cassini/ ] joins the Galileo spacecraft [ http://www.jpl.nasa.gov/galileo/mission.html] currently in orbit around Jupiter in studying the gas giant and its moons. In fact, observations [ http://www.jpl.nasa.gov/releases/2000/glextended.html ] involving both spacecraft [ http://www.jpl.nasa.gov/jupiterflyby/ ] simultaneously are planned in the coming months. This color picture [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02972 ] was taken when Cassini was 81.3 million kilometers from Jupiter. The alternating dark and bright bands characteristic of Jupiter's cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ] can be easily seen. Jupiter's moon Europa [ http://antwrp.gsfc.nasa.gov/apod/ap000825.html ] is also seen at the far right of the image casting a round shadow on the planet. |
|
Phobos: Doomed Moon of Mars
| Title |
Phobos: Doomed Moon of Mars |
| Explanation |
This moon is doomed. Mars [ http://mars.jpl.nasa.gov/extreme/index.html ], the red planet named for the Roman god of war [ http://www.pantheon.org/articles/m/mars.html ], has two tiny moons, Phobos [ http://www.nineplanets.org/phobos.html ] and Deimos [ http://www.nineplanets.org/deimos.html ], whose names are derived from the Greek for Fear and Panic. These martian moons [ http://antwrp.gsfc.nasa.gov/apod/ap031024.html ] may well be captured asteroids [ http://www.solarviews.com/eng/asteroid.htm ] originating in the main asteroid belt between Mars and Jupiter [ http://www.jpl.nasa.gov/galileo/jupiter/ jupiter.html ] or perhaps from even more distant reaches of the Solar System. The larger moon, Phobos [ http://antwrp.gsfc.nasa.gov/apod/ap030329.html ], is indeed seen to be a cratered, asteroid-like object in this stunning color image [ http://www.esa.int/SPECIALS/Mars_Express/ SEM21TVJD1E_0.html ] from the Mars Express spacecraft, recorded at a resolution of about seven meters per pixel. But Phobos orbits so close to Mars - about 5,800 kilometers above the surface compared to 400,000 kilometers for our Moon [ http://antwrp.gsfc.nasa.gov/apod/ap020504.html ] - that gravitational tidal forces [ http://csep10.phys.utk.edu/astr161/lect/moon/ tidal.html ] are dragging it down. In 100 million years or so it will likely crash into the surface or be shattered by stress caused by the relentless [ http://www.badastronomy.com/bad/misc/tides.html ] tidal forces, the debris forming a ring around Mars. |
|
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. |
|
Io: The Prometheus Plume
| Title |
Io: The Prometheus Plume |
| Explanation |
What's happening on Jupiter's moon Io? Two sulfurous eruptions are visible on Jupiter's volcanic moon Io [ http://antwrp.gsfc.nasa.gov/apod/ap040502.html ] in this color composite image [ http://photojournal.jpl.nasa.gov/catalog/PIA00703 ] from the robotic Galileo spacecraft [ http://en.wikipedia.org/wiki/Galileo_spacecraft ] that orbited Jupiter from 1995 to 2003. At the image top, over Io [ http://en.wikipedia.org/wiki/Io_%28moon%29 ]'s limb, a bluish plume rises about 140 kilometers above the surface of a volcanic caldera [ http://www.op.dlr.de/ne-hf/SRL-1/p44422-caldera.html ] known as Pillan Patera [ http://pirlwww.lpl.arizona.edu/~turtle/Releases/7Oct_pillan.html ]. In the image middle, near the night/day shadow line, the ring shaped Prometheus plume is seen rising about 75 kilometers above Io [ http://antwrp.gsfc.nasa.gov/apod/ap030120.html ] while casting a shadow below the volcanic [ http://antwrp.gsfc.nasa.gov/apod/ap051002.html ] vent. Named for the Greek god [ http://www.pantheon.org/articles/p/prometheus.html ] who gave mortals fire [ http://en.wikipedia.org/wiki/Fire ], the Prometheus [ http://en.wikipedia.org/wiki/Prometheus ] plume is visible in every image ever made of the region dating back to the Voyager flybys [ http://nssdc.gsfc.nasa.gov/imgcat/html/ object_page/vg1_1636836.html ] of 1979 - presenting the possibility that this plume has been [ http://antwrp.gsfc.nasa.gov/apod/ap970428.html ] continuously active for at least 18 years. The above digitally sharpened [ http://en.wikipedia.org/wiki/Unsharp_mask ] image was originally recorded in 1997 on June 28 from a distance of about 600,000 kilometers. |
|
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. |
|
Long Leonid
| Title |
Long Leonid |
| Explanation |
Just last week this long lovely Leonid shower [ http://spacescience.com/headlines/y2000/ ast21nov_1.htm ] meteor arced through the night. Captured on [ http://www.comet-track.com/meteor/leonids00/ leonids00.html ] November 17/18 by photographer [ http://www.comet-track.com ] Bob Yen, the meteor trail spans about 70 times the apparent diameter of the full moon in the skies above Mt. Wilson, California, USA. The Leonid's path flashes from the outskirts of constellation Gemini [ http://www.seds.org/Maps/Stars_en/Fig/ gemini.html ] to the triangle-shaped head of Taurus [ http://www.astro.uiuc.edu/~kaler/sow/ taurus-p.html ] (lower right). Of course, the trail points back toward Leo, the shower's [ http://comets.amsmeteors.org/meteors/showers/ leonids.html ] eponymous radiant, while passing near such night sky notables as galactic star cluster M35 [ http://www.seds.org/messier/m/m035.html ] (upper left) and Taurus's brightest star, red giant Aldebaran [ http://www.astro.uiuc.edu/~kaler/sow/ aldebaran.html ]. Though the sky was ruled by a bright but waning Moon and brilliant Jupiter, the Leonid meteor shower [ http://www.spaceweather.com/meteors/gallery_18nov00.html ] still awed observers at dark sky locations with peak rates of hundreds of meteors per hour. |
|
Oceans Under Jupiter's Moon
…
| 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. |
|
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 ]. |
|
Europa Rotating
| Title |
Europa Rotating |
| Explanation |
Evidence has been mounting that beneath the vast planes of ice that cover Europa [ http://antwrp.gsfc.nasa.gov/apod/ap961120.html ] lies water -- liquid oceans that might be home to alien life [ http://www.sciam.com/0497issue/0497scicit7.html ]. The smallest of Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ]'s Galilean Moons [ http://solarviews.com/eng/galdisc.htm ] (which include Io [ http://www.seds.org/nineplanets/nineplanets/io.html ], Ganymede [ http://www.seds.org/nineplanets/nineplanets/ganymede.html ], and Callisto [ http://www.seds.org/nineplanets/nineplanets/callisto.html ]), Europa's deep interior is composed of mostly of silicate rock [ http://windows.arc.nasa.gov/cgi-bin/tour_def/glossary/silicate_rock.html ]. Upon close inspection, many surface cracks [ http://antwrp.gsfc.nasa.gov/apod/ap980310.html ] stop abruptly only to continue on somewhere else -- indicating surface plates that might be sliding [ http://antwrp.gsfc.nasa.gov/apod/ap970410.html ]. The above time-lapse sequence [ http://www.solarviews.com/cap/jup/veuropa1.htm ] is a composite of images taken during the Voyager spacecraft [ http://vraptor.jpl.nasa.gov/voyager/voyager_fs.html ] flyby of the moon twenty years ago. Not all regions are resolved in high detail. The movie shows Europa [ http://www.seds.org/nineplanets/nineplanets/europa.html ] during a complete rotation, which corresponds to a complete revolution around Jupiter [ http://www.jpl.nasa.gov/galileo/Jovian.html ] since Europa [ http://cass.jsc.nasa.gov/pub/research/outerp/euro.html ] always keeps the same face toward the giant planet. The cause of many of the surface colors on Europa [ http://www.solarviews.com/eng/europa.htm ] also remains a topic of research [ http://antwrp.gsfc.nasa.gov/apod/ap010116.html http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1988Icar...75..437B ]. |
|
Jupiter Moon Movie
| Title |
Jupiter Moon Movie |
| Explanation |
South is toward the top in this frame from a stunning movie featuring Jupiter and moons recorded last Thursday from the Central Coast of New South Wales, Australia. In fact, three jovian moons [ http://antwrp.gsfc.nasa.gov/apod/ap001118.html ] and two red spots are ultimately seen in the full video as they glide around [ http://skytonight.com/observing/objects/javascript/ 3307071.html ] the solar system's ruling gas giant. In the early frame above, Ganymede [ http://www.nineplanets.org/ganymede.html ], the largest moon in the solar system, is off the lower right limb of the planet, while intriguing Europa [ http://www2.jpl.nasa.gov/galileo/moons/europa.html ] is visible against Jupiter's cloud tops, also near the lower right. Jupiter's new red spot junior [ http://redspotjr.christone.net/ ] is just above the broad white band in the planet's southern (upper) hemisphere. In later frames, as planet and moons rotate (right to left), red spot junior moves behind Jupiter's left edge while the Great Red Spot [ http://heritage.stsci.edu/1999/29/index.html ] itself comes into view from the right. Also finally erupting into view at the right, is Jupiter's volcanic moon, Io [ http://www.nineplanets.org/io.html ]. To download the full 2 megabyte movie as an animated gif file, click on the picture. |
|
New Horizons at Io
| Title |
New Horizons at Io |
| Explanation |
Spewed from a volcano [ http://volcano.und.edu/volcanoes.html ], a complex plume rises over 300 kilometers above the horizon of Jupiter's moon Io in this image from cameras onboard the New Horizons [ http://pluto.jhuapl.edu/index.php ] spacecraft. The volcano, Tvashtar [ http://www.planetaryexploration.net/jupiter/io/ lava_fountains.html ], is marked by the bright glow [ http://antwrp.gsfc.nasa.gov/apod/ap000606.html ] (about 1 o'clock) at the moon's edge, beyond the terminator or night/day shadow line. The shadow of Io cuts across the plume itself. Also capturing stunning details on the dayside surface, the high resolution image [ http://pluto.jhuapl.edu/gallery/missionPhotos/pages/ 031307.html ] was recorded when the spacecraft was 2.3 million kilometers from Io. Later it was combined with lower resolution color data [ http://pluto.jhuapl.edu/gallery/missionPhotos/pages/ 032807.html ] by astro-imager Sean Walker to produce this sharp portrait of the solar system's most active moon [ http://www.nineplanets.org/io.html ]. Outward bound at almost 23 kilometers "per second", the New Horizons spacecraft should cross the orbit of Saturn in June next year, and is ultimately destined [ http://pluto.jhuapl.edu/mission/passingplanets/ passingPlanets_current.php ] to encounter Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap060624.html ] in 2015. |
|
Nashville Four Planet Skylin
…
| 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. |
|
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 ]. |
|
Looking Back at an Eclipsed
…
| 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. |
|
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. |
|
Eris: More Massive than Plut
…
| Title |
Eris: More Massive than Pluto |
| Explanation |
Eris [ http://en.wikipedia.org/wiki/Eris_%28dwarf_planet%29 ], a dwarf planet [ http://en.wikipedia.org/wiki/Dwarf_planet ] currently orbiting the Sun at about twice Pluto's distance, has been measured [ http://hubblesite.org/newscenter/archive/releases/2007/24 ] to have about 27 percent more mass than Pluto. The mass was calculated by timing the orbit of Eris' moon Dysnomia [ http://en.wikipedia.org/wiki/Dysnomia_(moon) ]. Images taken with a ground-based Keck telescope [ http://antwrp.gsfc.nasa.gov/apod/ap971227.html ], when combined with existing images taken by Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ], show that Dysnomia has a nearly circular orbit lasting about 16 days. Cataloged as 2003 UB313 only a year ago, infrared images [ http://science.hq.nasa.gov/kids/imagers/ems/infrared.html ] also showed previously that Eris is actually larger in diameter than Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap060903.html ]. The plane of Eris' orbit is well out of the plane of the Solar System [ http://nineplanets.org/overview.html ]'s planets. In the above drawing, a scientific artist has imagined Eris and Dysnomia orbiting our distant Sun. No space missions are currently planned to Eris, although the robotic New Horizons [ http://en.wikipedia.org/wiki/New_Horizons ] spacecraft bound for Pluto [ http://pluto.jhuapl.edu/overview/faqs.php ] has recently passed Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap070307.html ]. |
|
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. |
|
Solar System Web Cam
| Title |
Solar System Web Cam |
| Explanation |
Ranging throughout the solar system [ http://space.jpl.nasa.gov/ ], these pictures all have something in common. They were taken with an 8 inch diameter telescope, a size popular with amateur astronomy buffs, and slightly modified "web cam" of the type widely used to send images out over the internet. The results are clearly remarkable for [ http://www.djcash.demon.co.uk/astro/webcam/webcam.htm ] such inexpensive and readily available equipment. Each sharp image was produced from 20 to 30 frames which were digitally stacked and processed using free software [ http://utopia.ision.nl/users/rjstek/english/software/ index.htm ]. Until recently, digital imaging for amateur astronomers required a specialized camera [ http://www.wvi.com/~rberry/cookbook.htm ], but the advent of low-light video surveillance cameras and web cams now presents other options for relatively bright [ http://www.astrabio.demon.co.uk/QCUIAG/ac/3dmoon.htm ] solar system objects. Want to try some unconventional [ http://www.astrabio.demon.co.uk/QCUIAG/ ] web cam astronomy? Geoff Chester, Public Affairs Officer at the U.S. Naval Observatory [ http://www.usno.navy.mil ], offers these images and an account of his own adventures [ http://www.usno.navy.mil/pao/QuickCamAstro.shtml ] from a suburban front lawn near Washington D.C. |
|
A Total Eclipse Over Africa
| Title |
A Total Eclipse Over Africa |
| Explanation |
What's that dark spot on the Sun? It's the Moon. Last month, on June 21, a total solar eclipse [ http://antwrp.gsfc.nasa.gov/apod/ap010706.html ] was visible in parts of Africa. In one of the most spectacular records of this eclipse [ http://antwrp.gsfc.nasa.gov/apod/ap010622.html ], Cees Bassa captured the setting Sun [ http://antwrp.gsfc.nasa.gov/apod/ap000320.html ] being eclipsed [ http://www.exploratorium.com/eclipse/zambia/index.html ] in a series of multiple exposures from Malambanyama [ http://www.humana.org/projekterne/childrens_town_malambanyama.htm ], Zambia [ http://www.cia.gov/cia/publications/factbook/geos/za.html ]. All of the images were taken 20 minutes apart, and all but the central image were taken though a dark solar filter [ http://www.skypub.com/sights/eclipses/solar/safety.html ]. Without the filter, the central image features the enormous flowing corona [ http://antwrp.gsfc.nasa.gov/apod/ap010408.html ] that surrounds the Sun [ http://www.nineplanets.org/sol.html ]. The planet Jupiter [ http://www.nineplanets.org/jupiter.html ] can be seen superposed just to the left of the next image after totality. |
|
Io in True Color
| Title |
Io in True Color |
| Explanation |
The strangest moon in the Solar System [ http://www.nineplanets.org/overview.html ] is bright yellow. This picture [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02308 ], showing Io's true colors, was taken in 1999 July by the Galileo spacecraft [ http://www.jpl.nasa.gov/galileo/spacecraft.html ] currently orbiting Jupiter. Io's colors derive from sulfur [ http://chemlab.pc.maricopa.edu/periodic/S.html ] and molten silicate rock [ http://www.windows.ucar.edu/cgi- bin/tour_def/glossary/silicate_rock.html ]. The unusual surface of Io [ http://antwrp.gsfc.nasa.gov/apod/ap961029.html] is kept very young by its system of active volcanoes [ http://antwrp.gsfc.nasa.gov/apod/ap960805.html ]. The intense tidal gravity [ http://www.clupeid.demon.co.uk/tides/simple.html ] of Jupiter [ http://www.solarviews.com/eng/jupiter.htm ] stretches Io [ http://antwrp.gsfc.nasa.gov/apod/ap981016.html ] and damps wobbles caused by Jupiter's other Galilean moons [ http://www.jpl.nasa.gov/galileo/ganymede/discovery.html ]. The resulting friction [ http://www.pa.uky.edu/~phy211/Friction_book.html ] greatly heats Io [ http://antwrp.gsfc.nasa.gov/apod/ap980706.html ]'s interior, causing molten rock [ http://cmex.arc.nasa.gov/data/catalog/VolcanismOnMars/MoltenRock.html ] to explode through the surface. Io's volcanoes [ http://antwrp.gsfc.nasa.gov/apod/ap000606.html ] are so active that they are effectively turning the whole moon inside out. Some of Io [ http://www.nineplanets.org/io.html ]'s volcanic lava is so hot it glows in the dark [ http://adsabs.harvard.edu/cgi-bin/nph- bib_query?bibcode=1998Icar..135..181M ]. |
|
Phobos: Doomed Moon of Mars
| Title |
Phobos: Doomed Moon of Mars |
| Explanation |
Mars [ http://mars.jpl.nasa.gov/extreme/index.html ], the red planet named for the Roman god of war, has two tiny moons, Phobos [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ phobos.html ] and Deimos [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ deimos.html ], whose names are derived from the Greek for Fear and Panic. These Martian moons [ http://www.seds.org/billa/tnp/hypo.html#mars ] may well be captured asteroids [ http://www.seasky.org/solarsystem/sky3k.html ] originating in the main asteroid belt between Mars and Jupiter [ http://www.jpl.nasa.gov/galileo/jupiter/ jupiter.html ] or perhaps from even more distant reaches of the Solar System [ http://space.jpl.nasa.gov/ ]. In this 1978 Viking 1 orbiter image [ http://nssdc.gsfc.nasa.gov/photo_gallery/caption/ vik_phobos_caption.html ], the largest moon, Phobos [ http://seds.lpl.arizona.edu/nineplanets/ nineplanets/phobos.html ], is indeed seen to be a heavily cratered asteroid-like object. About 17 miles across, Phobos really zips [ http://antwrp.gsfc.nasa.gov/apod/ap991105.html ] through the Martian sky. Actually rising above Mars' western horizon and setting in the east, it completes an orbit in less than 8 hours. But Phobos is doomed. Phobos orbits so close to Mars, (about 3,600 miles above the surface compared to 250,000 miles for our Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010127.html ]) that gravitational tidal forces are dragging it down. In 100 million years or so it will likely crash into the surface or be shattered by stress caused by the relentless tidal forces [ http://www.badastronomy.com/bad/misc/tides.html ], the debris forming a ring around Mars. |
|
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 ]. |
|
Jagged Hills on Jupiter's Ca
…
| Title |
Jagged Hills on Jupiter's Callisto |
| Explanation |
Why does Jupiter's moon Callisto have unusual jagged hills? This mystery came to light after the robot spacecraft [ http://galileo.jpl.nasa.gov/mission/space-intro.html ] Galileo [ http://galileo.jpl.nasa.gov/mission/mission.html ], in orbit around Jupiter [ http://www.nineplanets.org/jupiter.html ] since 1995, swooped past the dark moon [ http://antwrp.gsfc.nasa.gov/apod/ap980512.html ] in May. The resulting pictures [ http://www.jpl.nasa.gov/images/callisto/callisto_terrain_caption.html ] were the highest resolution yet obtained for a Jovian moon [ http://galileo.jpl.nasa.gov/moons/moons.html ]: objects as small as 3 meters across are discernable. The strange landscapes pictured above [ http://antwrp.gsfc.nasa.gov/apod/ap010828.html http://galileo.jpl.nasa.gov/news/release/press010822.html ] show areas rich in bright sharp mounds about 100 meters tall. A likely formation hypothesis [ http://galileo.jpl.nasa.gov/news/release/press010822.html ] holds that these hills are the result of ejecta thrown billions of years ago during a violent impact [ http://antwrp.gsfc.nasa.gov/apod/ap990711.html ]. The lower inset region apparently has undergone an epoch of relatively high ice-erosion [ http://members.edventures.com/terms/e/erosion/definition.html ], where dark rock has filled in some of the inter-hill regions. NASA [ http://www.nasa.gov/ ] has recently cleared Galileo [ http://galileo.jpl.nasa.gov/news/release/press010315.html ] to continue swooping Jupiter's moons [ http://www.sciam.com/2000/0200issue/0200johnson.html ] until 2003, when it will end its journey [ http://galileo.jpl.nasa.gov/news/release/press010315.html ] with a spectacular dive [ http://antwrp.gsfc.nasa.gov/apod/ap951208.html ] into Jupiter's atmosphere [ http://antwrp.gsfc.nasa.gov/apod/ap000429.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 Newly Active Volcano on Ju
…
| Title |
A Newly Active Volcano on Jupiter's Io |
| Explanation |
Would a volcano plume discovered in January above Jupiter's Moon Io still be active months later? To answer this question, the robot spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/overview.html ] currently in orbit around Jupiter [ http://www.nineplanets.org/jupiter.html ] was maneuvered to image the plume [ http://antwrp.gsfc.nasa.gov/apod/ap970818.html ] site during its recent flyby of Io [ http://www.nineplanets.org/io.html ] in August. What was found was the highest volcano plume yet discovered [ http://www.jpl.nasa.gov/images/io/caption_ioplume_1004.html ] -- but above a completely different and previously undocumented volcano! The original plume [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02584 ], above the Tvashtar Catena [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02550 ] volcanic area, was not even visible. A picture taken in January [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02588 ] of the area surrounding the Tvashtar Catena eruption is shown above in enhanced color, with a new picture taken in August [ http://www.jpl.nasa.gov/images/io/caption_ioplume_1004.html ] shown in the inset. Careful inspection of the two images will show a newly prominent dark volcano [ http://antwrp.gsfc.nasa.gov/apod/ap991126.html ] surrounded by a light-colored ring visible only in the smaller, more recent image [ http://www.jpl.nasa.gov/releases/2001/release_2001_192.html ]. |
|
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 ]. |
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Jupiter's Rings Revealed
| Title |
Jupiter's Rings Revealed |
| Explanation |
Why does Jupiter have rings? Jupiter's rings [ http://www2.jpl.nasa.gov/galileo/rings/ ] were discovered in 1979 by the passing Voyager 1 spacecraft [ http://voyager.jpl.nasa.gov/ ], but their origin was a mystery. Data [ http://www.jpl.nasa.gov/galileo/status980915.html ] from the Galileo spacecraft [ http://www2.jpl.nasa.gov/galileo/spacecraft.html ] that orbited Jupiter [ http://www.nineplanets.org/jupiter.html ] from 1995 to 2003 [ http://www2.jpl.nasa.gov/galileo/mission_end.html ] later confirmed that these rings were created by meteoroid impacts [ http://www.nineplanets.org/meteorites.html ] on small nearby moons [ http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=Moons ]. As a small meteoroid strikes tiny Adrastea [ http://en.wikipedia.org/wiki/Adrastea_%28moon%29 ], for example, it will bore into the moon, vaporize, and explode dirt and dust off into a Jovian orbit [ http://www.news.cornell.edu/releases/sept98/jupiter_rings.html ]. Pictured above [ http://photojournal.jpl.nasa.gov/catalog/pia01621 ] is an eclipse of the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap010620.html ] by Jupiter, as viewed from Galileo. Small dust particles high in Jupiter's atmosphere [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ], as well as the dust particles [ http://antwrp.gsfc.nasa.gov/apod/ap010813.html ] that compose the rings [ http://antwrp.gsfc.nasa.gov/apod/ap970807.html ], can be seen by reflected sunlight [ http://antwrp.gsfc.nasa.gov/apod/ap000624.html ]. |
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