|
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Lightning on Earth
| Title |
Lightning on Earth |
| Explanation |
Nobody knows what causes lightning. It is known that charges [ http://physics.bu.edu/~duffy/PY106/Charge.html ] slowly separate in some clouds [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml ] causing rapid electrical discharges [ http://www.eng.tau.ac.il/Pages/Departments/Inter/edp_lab/ ] (lightning), but how electrical charges [ http://physicsstudio.indstate.edu/java/potential/ProyectI.html ] get separated in clouds [ http://www.geo.mtu.edu/department/classes/ge406/tjbrabec/cloud.html ] remains a topic of much research. Nevertheless, lightning [ http://wvlightning.com/info.html ] bolts are common in clouds during rainstorms, and on average 6000 lightning bolts occur between clouds and the Earth every minute. Above [ http://www.noao.edu/image_gallery/html/im0426.html ], several lightning strokes were photographed behind Kitt Peak National Observatory [ http://www.noao.edu/outreach/kpoutreach.html ] in Arizona [ http://www.state.az.us/ ]. Lightning [ http://bondo.wsc.mass.edu/dept/garp/faculty/lightn.htm ] has also been found on the planets Venus [ http://www.lpl.arizona.edu/~hansell/lightning/poster.html ], Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap971216.html ], Saturn [ http://learn.jpl.nasa.gov/projectspacef/bkg130b.html ], and Uranus [ http://www.spacetoday.org/SolSys/Uranus/Uranus.html ]. NASA [ http://www.nasa.gov/ ] launched the TRMM mission [ http://trmm.gsfc.nasa.gov/news.html ] in 1997 that continues to measure rainfall and lightning [ http://thunder.msfc.nasa.gov/primer/ ] on planet Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990131.html ]. |
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Eight Planets and New Solar
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| Title |
Eight Planets and New Solar System Designations |
| Explanation |
How many planets are in the Solar System? This popular question now has a new formal answer according the International Astronomical Union [ http://en.wikipedia.org/wiki/International_Astronomical_Union ] (IAU): eight. Last week, the IAU voted [ http://www.iau2006.org/mirror/www.iau.org/iau0603/index.html ] on a new definition for planet [ http://www.iau2006.org/mirror/www.iau.org/iau0603/index.html ] and Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap010319.html ] did not make the cut. Rather, Pluto was re-classified as a dwarf planet [ http://en.wikipedia.org/wiki/Dwarf_planet ] and is considered as a prototype for a new category of trans-Neptunian objects [ http://en.wikipedia.org/wiki/Trans-Neptunian_object ]. The eight planets now recognized by the IAU are: Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap040912.html ], Venus [ http://antwrp.gsfc.nasa.gov/apod/ap040516.html ], Earth [ http://antwrp.gsfc.nasa.gov/apod/ap050102.html ], Mars [ http://antwrp.gsfc.nasa.gov/apod/ap060730.html ], Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap050911.html ], Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap041225.html ], Uranus [ http://antwrp.gsfc.nasa.gov/apod/ap010826.html ], and Neptune [ http://antwrp.gsfc.nasa.gov/apod/ap010821.html ]. Solar System objects now classified as dwarf planets are: Ceres [ http://antwrp.gsfc.nasa.gov/apod/ap060821.html ], Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap060624.html ], and the currently unnamed 2003 UB313 [ http://antwrp.gsfc.nasa.gov/apod/ap060207.html ]. Planets, by the new IAU definition, must be in orbit around the sun, be nearly spherical, and must have cleared the neighborhood around their orbits. The demotion of Pluto [ http://www.nineplanets.org/pluto.html ] to dwarf planet status is a source of continuing dissent [ http://www.badastronomy.com/bablog/2006/08/18/colbert-takes-neil-tyson-down/ ] and controversy [ http://newswire.ascribe.org/cgi-bin/behold.pl?ascribeid=20060818.063045&time=07%2006%20PDT&year=2006&public=0 ] in the astronomical community. |
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Steep Cliffs on Mars
| Title |
Steep Cliffs on Mars |
| Explanation |
Vertical cliffs of nearly two kilometers occur near the North Pole of Mars. Also visible in the above image [ http://www.esa.int/SPECIALS/Mars_Express/SEMLF6D3M5E_1.html ] of the Martian North Polar Cap [ http://antwrp.gsfc.nasa.gov/apod/ap021224.html ] are red areas of rock and sand, white areas of ice, and dark areas of unknown composition but hypothesized to be volcanic ash [ http://volcanoes.usgs.gov/Products/Pglossary/ash.html ]. The cliffs are thought to border volcanic caldera [ http://antwrp.gsfc.nasa.gov/apod/ap040526.html ]. Although the sheer drop [ http://antwrp.gsfc.nasa.gov/apod/ap970218.html ] of the Martian cliffs is extreme, the drop is not as deep as other areas in our Solar System [ http://www.nineplanets.org/overview.html ], including the 3.4-kilometer depth of Colca Canyon [ http://www.bootsnall.com/articles/02-08/where-is-the-deepest-canyon-in-the-world-arequipa-peru.html ] on Earth and the 20 kilometer depth of Verona Rupes [ http://en.wikipedia.org/wiki/Verona_Rupes ] on Uranus' moon Miranda [ http://astrogeology.usgs.gov/Projects/BrowseTheGeologicSolarSystem/MirandaBack.html ]. The above image [ http://www.esa.int/SPECIALS/Mars_Express/SEMLF6D3M5E_0.html ], digitally reconstructed into a perspective view [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005LPI....36.1769S ], was taken by the High Resolution Stereo Camera [ http://berlinadmin.dlr.de/Missions/express/kamera/kameraeng.shtml ] on board the ESA [ http://www.esa.int/ ]'s robotic Mars Express spacecraft [ http://www.esa.int/esaSC/120379_index_0_m.html ] currently orbiting Mars [ http://www.nineplanets.org/mars.html ]. |
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Verona Rupes: Tallest Known
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| Title |
Verona Rupes: Tallest Known Cliff in the Solar System |
| Explanation |
Could you survive a jump off the tallest cliff in the Solar System? Quite possibly. Verona Rupes [ http://en.wikipedia.org/wiki/Verona_Rupes ] on Uranus [ http://www.nineplanets.org/uranus.html ]' moon Miranda [ http://www.nineplanets.org/miranda.html ] is estimated to be 20 kilometers deep -- ten times the depth of the Earth's Grand Canyon [ http://www.nps.gov/grca/ ]. Given Miranda [ http://en.wikipedia.org/wiki/Miranda_%28moon%29 ]'s low gravity, it would take about 12 minutes for a thrill-seeking adventurer [ http://video.google.com/videoplay?docid=2090669779765584576 ] to fall from the top, reaching the bottom at the speed of a racecar -- about 200 kilometers per hour. Even so, the fall might be survivable given proper airbag [ http://www.howstuffworks.com/airbag.htm ] protection. The above image [ http://photojournal.jpl.nasa.gov/catalog/PIA00044 ] of Verona Rupes was captured by the passing Voyager [ http://antwrp.gsfc.nasa.gov/apod/ap020831.html ] 2 robotic spacecraft in 1986. How the giant cliff was created remains unknown, but is possibly related to a large impact [ http://antwrp.gsfc.nasa.gov/apod/ap050308.html ] or tectonic [ http://en.wikipedia.org/wiki/Extensional_tectonics ] surface motion. |
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Venus: Earth's Sister Planet
| Title |
Venus: Earth's Sister Planet |
| Explanation |
This picture in visible light was taken by the Galileo [ http://nssdc.gsfc.nasa.gov/planetary/galileo.html ] spacecraft. Venus [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/venus.html ] is very similar to Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ] in size and mass - and so is sometimes referred to as Earth's sister planet - but Venus has a quite different climate. Venus' [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/venus.html ] thick clouds and closeness to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ] (only Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap950814.html ] is closer) make it the hottest planet - much hotter than the Earth. Humans could not survive there, and no life of any sort has ever been found. When Venus [ http://nssdc.gsfc.nasa.gov/photo_gallery/PhotoGallery-Venus.html ] is visible it is usually the brightest object in the sky after the Sun and the Moon. More than 20 spacecraft have visited Venus including Venera 9, which landed on the surface, and Magellan [ http://stardust.jpl.nasa.gov/mveg/guide.html ], which used radar to peer through the clouds and make a map of the surface. There are still many things about Venus's unusual atmosphere that astronomers don't understand. Tomorrow's picture: Uranus: The Tilted Planet |
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Uranus' Largest Moon: Titani
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| Title |
Uranus' Largest Moon: Titania |
| Explanation |
Titania's tortured terrain is a mix of valleys and craters. NASA's interplanetary robot spacecraft Voyager [ http://spacelink.msfc.nasa.gov/NASA.Projects/Planetary.Probes/Voyager/Mission.Summary ] 2 passed this moon of Uranus [ http://antwrp.gsfc.nasa.gov/apod/ap950816.html ] in 1986 and took the above photograph. The photograph was then transmitted back to earth by radio [ http://www.science.uwaterloo.ca/physics/p13news/number_2/maxnew-2.html ]. The valleys of Titania [ http://bang.lanl.gov/solarsys/titania.htm ] resemble those on Ariel [ http://antwrp.gsfc.nasa.gov/apod/ap960303.html ] indicate that Titania underwent some unknown tumultuous resurfacing event in its distant past. Although Titania [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/titania.html ] is Uranus' largest moon, it is still much smaller than Triton [ http://antwrp.gsfc.nasa.gov/apod/ap950805.html ] - the largest moon of Uranus' sister planet Neptune [ http://antwrp.gsfc.nasa.gov/apod/ap950817.html ]. Titania is essentially a large dirty iceball that orbits Uranus - it is composed of about half water-ice and half rock. Titania was discovered by William Hershel [ http://www.dsi.unimi.it/Users/Students/amoroso/sun/fortunes/life-e.html ] in 1787. |
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Alpha Centauri: The Closest
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| Title |
Alpha Centauri: The Closest Star System |
| Explanation |
The closest star system to the Sun is the Alpha Centauri system [ http://monet.physik.unibas.ch/~schatzer/Alpha-Centauri.html ]. Of the three stars in the system, the dimmest -- called Proxima Centauri -- is actually the nearest star [ http://cassfos02.ucsd.edu/public/nearest.html ]. The bright stars Alpha Centauri A and B form a close binary as they are separated by only 23 times the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ]- Sun [ http://antwrp.gsfc.nasa.gov/apod/ap960521.html ] distance - slightly greater than the distance between Uranus [ http://antwrp.gsfc.nasa.gov/apod/ap950816.html ] and the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ]. In the above picture, the brightness of the stars overwhelm the photograph causing an illusion of great size, even though the stars are really just small points of light. The Alpha Centauri system is not visible in much of the northern hemisphere. Alpha Centauri A, also known as Rigil Kentaurus [ http://www.astro.wisc.edu/~dolan/constellations/hr/5459.html ], is the brightest star in the constellation of Centaurus [ http://galileo.gmu.edu/constellation/CEN.html ] and is the fourth brightest star [ http://www.entrenet.com/mizar/brt_star.html ] in the night sky. Sirius [ http://www.astro.wisc.edu/~dolan/constellations/hr/2491.html ] is the brightest even thought it is more than twice as far away. By an exciting coincidence, Alpha Centauri A is the same type of star as our Sun, causing many to speculate that it might contain planets that harbor life. |
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Alpha Centauri: The Closest
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| Title |
Alpha Centauri: The Closest Star System |
| Explanation |
The closest star system to the Sun is the Alpha Centauri system [ http://homepage.sunrise.ch/homepage/schatzer/Alpha-Centauri.html ]. Of the three stars in the system, the dimmest -- called Proxima Centauri [ http://antwrp.gsfc.nasa.gov/apod/ap020715.html ] -- is actually the nearest star [ http://antwrp.gsfc.nasa.gov/apod/ap010318.html ]. The bright stars Alpha Centauri [ http://www.astro.uiuc.edu/~kaler/sow/rigil-kent.html ] A and B form a close binary [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ] as they are separated by only 23 times the Earth- Sun distance [ http://neo.jpl.nasa.gov/glossary/au.html ] - slightly greater than the distance between Uranus [ http://www.nineplanets.org/uranus.html ] and the Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ]. In the above picture [ http://www.eso.org/outreach/press-rel/pr-2003/pr-05-03.html ], the brightness of the stars overwhelm the photograph causing an illusion of great size, even though the stars are really just small points of light. The Alpha Centauri system [ http://www.eso.org/outreach/press-rel/pr-2003/pr-05-03.html ] is not visible in much of the northern hemisphere. Alpha Centauri A, also known as Rigil Kentaurus [ http://www.astro.wisc.edu/~dolan/constellations/hr/5459.html ], is the brightest star in the constellation of Centaurus [ http://www.astronomical.org/constellations/cen.html ] and is the fourth brightest star in the night sky. Sirius [ http://antwrp.gsfc.nasa.gov/apod/ap000611.html ] is the brightest even thought it is more than twice as far away. By an exciting coincidence, Alpha Centauri [ http://www.solstation.com/stars/alp-cent3.htm ] A is the same type of star as our Sun [ http://www.nineplanets.org/sol.html ], causing many to speculate [ http://homepage.sunrise.ch/homepage/schatzer/Alpha-Centauri.html ] that it might contain planets that harbor life. |
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Lightning on Jupiter
| Title |
Lightning on Jupiter |
| Explanation |
Does lightning occur only on Earth? Spacecraft in our Solar System have detected radio signals consistent with lightning [ http://wwwghcc.msfc.nasa.gov/lisotd.html ] on other planets, including Venus [ http://www.seds.org/nineplanets/nineplanets/venus.html ], Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ], Saturn [ http://www.seds.org/nineplanets/nineplanets/saturn.html ], Uranus [ http://www.seds.org/nineplanets/nineplanets/uranus.html ], and Neptune [ http://www.seds.org/nineplanets/nineplanets/neptune.html ]. In the above photograph [ http://galileo.ivv.nasa.gov/callisto/050197.html ], optical flashes from Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap970109.html ] were photographed recently by the Galileo orbiter [ http://galileo.ivv.nasa.gov/mission.html ]. Each of the circled dots indicates lightning [ http://www.nofc.forestry.ca/~kanderso/ltgfaq.html ]. The numbers label lines of latitude [ http://www.met.fsu.edu/explores/latlon.html ]. The size of the largest spot is about 500 kilometers across and might be high clouds illuminated by several bright lightning strokes. |
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An Auroral Ring on Jupiter
| Title |
An Auroral Ring on Jupiter |
| Explanation |
Do other planets have aurora? Terrestrial [ http://work.ucsd.edu:5141/cgi-bin/http_webster?terrestrial ] and spacecraft observations have found evidence for aurora on Venus [ http://www.seds.org/nineplanets/nineplanets/venus.html ], Mars [ http://antwrp.gsfc.nasa.gov/apod/ap970609.html http://www.seds.org/nineplanets/nineplanets/mars.html ], Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ], Saturn [ http://www.seds.org/nineplanets/nineplanets/saturn.html ], Uranus [ http://www.seds.org/nineplanets/nineplanets/uranus.html ], and Neptune [ http://www.seds.org/nineplanets/nineplanets/neptune.html ]. In the above false-color photograph [ http://galileo.ivv.nasa.gov/callisto/043097.html ], a good portion of an auroral ring [ http://antwrp.gsfc.nasa.gov/apod/ap970609.html http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996BAAS%2E%2E%2E28%2E2123P&db_key=AST&nosetcookie=1 ] was captured recently in optical light by the Galileo spacecraft [ http://galileo.ivv.nasa.gov/spacecraft.html ] in orbit around Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap970609.html http://antwrp.gsfc.nasa.gov/cgi-bin/cossc/apod_search?jupiter ]. Auroral rings [ http://antwrp.gsfc.nasa.gov/apod/ap970609.html http://www.geo.mtu.edu/weather/aurora/ ] encircle a planet's magnetic pole, and result from charged particles spiraling down magnetic field lines. Although the surroundings near Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap960803.html ] are much different than Earth [ http://antwrp.gsfc.nasa.gov/apod/ap961230.html ], the auroral rings [ http://antwrp.gsfc.nasa.gov/apod/ap970402.html ] appear similar. |
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Retrograde Mars
| Title |
Retrograde Mars |
| Explanation |
Why would Mars appear to move backwards? Most of the time, the apparent motion of Mars [ http://www.nineplanets.org/mars.html ] in Earth's sky [ http://antwrp.gsfc.nasa.gov/apod/ap010827.html ] is in one direction, slow but steady in front of the far distant stars. About every two years, however, the Earth passes Mars [ http://antwrp.gsfc.nasa.gov/apod/ap030902.html ] as they orbit around the Sun. During the most recent such pass in August, Mars loomed [ http://antwrp.gsfc.nasa.gov/apod/ap030828.html ] particularly large and bright [ http://antwrp.gsfc.nasa.gov/apod/ap030827.html ]. Also during this time, Mars appeared to move backwards in the sky, a phenomenon called retrograde motion [ http://alpha.lasalle.edu/~smithsc/Astronomy/retrograd.html ]. Pictured above is a series of images digitally stacked so that all of the stars images coincide. Here, Mars appears to trace out a loop [ http://mars.jpl.nasa.gov/allabout/nightsky/nightsky04.html ] in the sky. At the top of the loop, Earth passed Mars and the retrograde motion [ http://astron.berkeley.edu/~ay7/html/homework/hw1/node3.html ] was the highest. Retrograde motion [ http://antwrp.gsfc.nasa.gov/apod/ap011220.html ] can also be seen for other Solar System [ http://www.nineplanets.org/overview.html ] planets. In fact, by coincidence, the dotted line to the right of the image center is Uranus doing the same thing. |
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Solar System Portrait
| Title |
Solar System Portrait |
| Explanation |
On another Valentine's Day [ http://www.poets.org/poems/poems.cfm?prmID=1166 ] (February 14, 1990), cruising four billion miles from the Sun, the Voyager 1 [ http://antwrp.gsfc.nasa.gov/apod/ap031120.html ] spacecraft looked back to make this first ever family portrait [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA00451 ] of our Solar System. The complete portrait is a 60 frame mosaic [ http://nssdc.gsfc.nasa.gov/photo_gallery/ photogallery-solarsystem.html ] made from a vantage point 32 degrees above the ecliptic plane [ http://antwrp.gsfc.nasa.gov/apod/ap001014.html ]. Voyager's wide angle camera frames sweep through the inner Solar System (far left) linking up with gas giant Neptune, at the time the Solar System's [ http://www.seds.org/nineplanets/nineplanets/overview.html ] outermost planet (scroll right). Positions [ http://nssdc.gsfc.nasa.gov/image/planetary/solar_system/ family_diagram.jpg ] for Venus, Earth [ http://www.seds.org/billa/psc/pbd.html ], Jupiter, Saturn, Uranus, and Neptune are indicated by the corresponding letters while the Sun is the bright spot near the center of the circle of frames. The inset frames [ http://antwrp.gsfc.nasa.gov/apod/ap980517.html ] for each of the planets are from Voyager's narrow field camera. Unseen in the portrait are Mercury [ http://www.psrd.hawaii.edu/Jan97/Mercury Unveiled.html ], too close to the Sun to be detected, and Mars, unfortunately hidden by sunlight scattered in the camera's optical system. Small, faint Pluto's [ http://antwrp.gsfc.nasa.gov/apod/ap011018.html ] position was not covered. |
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Lightning on Earth
| Title |
Lightning on Earth |
| Explanation |
Nobody knows what causes lightning. It is known that charges [ http://physics.bu.edu/~duffy/PY106/Charge.html ] slowly separate in some clouds [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml ] causing rapid electrical discharges [ http://van.hep.uiuc.edu/van/qa/section/Electricity_and_Magnets/Stuff_that_Sparks/20020722034338.htm ] (lightning), but how electrical charges [ http://www.sciencemadesimple.com/static.html ] get separated in clouds [ http://www.geo.mtu.edu/department/classes/ge406/tjbrabec/cloud.html ] remains a topic of much research. Nevertheless, lightning [ http://wvlightning.com/info.html ] bolts are common in clouds during rainstorms, and on average 6000 lightning bolts occur between clouds and the Earth every minute. Above [ http://www.astro.umd.edu/openhouse/gallery/2004-07KPNO/index.html ], several lightning strokes were photographed under a starry sky behind Kitt Peak National Observatory [ http://www.noao.edu/outreach/kpoutreach.html ] near Tucson, Arizona [ http://www.state.az.us/ ]. Lightning [ http://www.nationalgeographic.com/lightning/ ] has also been found on the planets Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap971216.html ], Saturn [ http://news.bbc.co.uk/2/hi/science/nature/3920597.stm ], and Uranus [ http://www.spacetoday.org/SolSys/Uranus/UranusVoyager.html ]. NASA [ http://www.nasa.gov/ ] launched the TRMM mission [ http://trmm.gsfc.nasa.gov/ ] in 1997 that continues to measure rainfall and lightning [ http://thunder.msfc.nasa.gov/primer/ ] on planet Earth [ http://antwrp.gsfc.nasa.gov/apod/ap010204.html ]. |
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A Sharper View of a Tilted P
…
| Title |
A Sharper View of a Tilted Planet |
| Explanation |
These sharp views [ http://www2.keck.hawaii.edu/news/science/uranus/ index.html ] of tilted gas giant Uranus [ http://www.nineplanets.org/uranus.html ] show dramatic details of the planet's atmosphere and ring system [ http://ringmaster.arc.nasa.gov/uranus/uranus.html ]. The remarkable ground-based images [ http://www.news.wisc.edu/10402.html ] were made using a near-infrared camera and the Keck Adaptive Optics system to reduce the blurring effects of Earth's atmosphere. Recorded in July, the pictures show [ http://www.news.wisc.edu/newsphotos/ uranus2.html ] two sides of Uranus (careful how you pronounce [ http://www.nineplanets.org/say/uranus.au ] that ...). In both, high, white cloud features are seen mostly in the northern (right hand) hemisphere, with medium level cloud bands in green and lower level clouds in blue. The artificial color scheme lends a deep reddish tint to the otherwise faint rings [ http://antwrp.gsfc.nasa.gov/apod/ap030115.html ]. Because of the severe tilt of its rotational axis, seasons on Uranus [ http://www.haydenplanetarium.org/hp/vo/ava/avapages/ P0418uranseas.html ] are extreme and last nearly 21 Earth years on the distant planet [ http://nssdc.gsfc.nasa.gov/ planetary/factsheet/uranusfact.html ]. Uranus is now slowly approaching its southern autumnal equinox - the beginning of fall in the southern hemisphere - in 2007. |
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Steep Cliffs on Mars
| Title |
Steep Cliffs on Mars |
| Explanation |
Vertical cliffs of nearly two kilometers occur near the North Pole of Mars. Also visible in the above image [ http://www.esa.int/SPECIALS/Mars_Express/SEMLF6D3M5E_1.html ] of the Martian North Polar Cap [ http://antwrp.gsfc.nasa.gov/apod/ap021224.html ] are red areas of rock and sand, white areas of ice, and dark areas of unknown composition but hypothesized to be volcanic ash [ http://volcanoes.usgs.gov/Products/Pglossary/ash.html ]. The cliffs are thought to border volcanic caldera [ http://antwrp.gsfc.nasa.gov/apod/ap040526.html ]. Although the sheer drop [ http://antwrp.gsfc.nasa.gov/apod/ap970218.html ] of the Martian cliffs is extreme, the drop is not as deep as other areas in our Solar System [ http://www.nineplanets.org/overview.html ], including the 3.4-kilometer depth of Colca Canyon [ http://www.bootsnall.com/articles/02-08/where-is-the-deepest-canyon-in-the-world-arequipa-peru.html ] on Earth and the 20 kilometer depth of Verona Rupes [ http://www.guinnessworldrecords.com/content_pages/record.asp?recordid=54819 ] on Uranus' moon Miranda [ http://astrogeology.usgs.gov/Projects/BrowseTheGeologicSolarSystem/MirandaBack.html ]. The above image [ http://www.esa.int/SPECIALS/Mars_Express/SEMLF6D3M5E_0.html ], digitally reconstructed into a perspective view [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005LPI....36.1769S ], was taken by the High Resolution Stereo Camera [ http://berlinadmin.dlr.de/Missions/express/kamera/kameraeng.shtml ] on board the ESA [ http://www.esa.int/ ]'s robotic Mars Express spacecraft [ http://www.esa.int/esaSC/120379_index_0_m.html ] currently orbiting Mars [ http://www.nineplanets.org/mars.html ]. |
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Aerogel For STARDUST
| Title |
Aerogel For STARDUST |
| Explanation |
On February 7th, this honey comb [ http://stardust.jpl.nasa.gov/photo/spacecraft1.html ] of aluminum cells filled with aerogel [ http://www.Aerogels.com/ ] was launched on the STARDUST [ http://stardust.jpl.nasa.gov/ ] mission to interplanetary space. STARDUST's goal is to capture dust from a comet's tail and return to planet Earth - the first sample return [ http://stardust.jpl.nasa.gov/spacecraft/capsule.html ] mission to a comet [ http://encke.jpl.nasa.gov/ ]! This structure represents about 1,000 square centimeters of area for collecting dust trailing within 150 kilometers of the nucleus of P/Wild-2 [ http://stardust.jpl.nasa.gov/comets/wild1.html ]. Comet P/Wild-2 is new to the inner Solar System. Having spent its life in orbit between Jupiter and Uranus, this comet was deflected in 1974 by a close encounter with Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap980801.html ] and now orbits between Jupiter and Earth. Dust from P/Wild-2 should impact the aerogel at high speeds and come to rest leaving carrot-shaped [ http://antwrp.gsfc.nasa.gov/apod/ap981121.html ] tracks in this amazingly tough, transparent, ultra-low density [ http://stardust.jpl.nasa.gov/spacecraft/aerogel.html ] material. Returning to Earth by parachute in 2006, the cometary dust sample will be analyzed for clues to [ http://stardust.jpl.nasa.gov/science/sd-value.html ] the formation and primordial composition of our Solar System. |
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A Solar System Portrait
| Title |
A Solar System Portrait |
| Explanation |
As the Voyager 1 spacecraft [ http://vraptor.jpl.nasa.gov/voyager/vgrfaqs.html ] headed out of our Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap980517.html ], it looked back and took a parting family portrait [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-solarsystem.html ] of the Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ] and planets. From beyond Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap990213.html ], our Solar System looks like a bright star surrounded by faint dots. In the above picture [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA00451 ], the Sun is so bright it is blocked out for contrast. The innermost dots visible, labeled E and V for Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990131.html ] and Venus [ http://www.nasm.edu/ceps/RPIF/VENUS/rpifvenus.html ], are particularly hard to discern. Gas giants Jupiter [ http://www.jpl.nasa.gov/galileo/Jovian.html ] (J) and Saturn [ http://www.seds.org/nineplanets/nineplanets/saturn.html ] (S) are much more noticeable. The outermost planets visible are Uranus [ http://www.hawastsoc.org/solar/eng/uranus.htm ] (U) and Neptune [ http://antwrp.gsfc.nasa.gov/apod/ap980221.html ] (N). Each planet is shown labeled and digitally enhanced in an inset image. Voyager 1 is only one of four human-made objects to leave our Solar System, the other three being Voyager 2, and Pioneer 10 and Pioneer 11. |
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