The Exploration of Space Saturn and its Moons. Space Words Planet Moon Sun Star Solar System Orbit.
Moons of Saturn - Jet Propulsion Laboratory Aeronautics and Space Administration Moons of Saturn...
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www.nasa.gov Moons of Saturn National Aeronautics and Space Administration 300,000,000 900,000,000 1,500,000,000 2,100,000,000 2,700,000,000 3,300,000,000 3,900,000,000 4,500,000,000 5,100,000,000 5,700,000,000 kilometers 0
Transcript of Moons of Saturn - Jet Propulsion Laboratory Aeronautics and Space Administration Moons of Saturn...
National Aeronautics and Space Administration
www.nasa.gov
Moons of Saturn
National Aeronautics and Space Administration
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LG-2009-09-576-HQ — JPL 400-1344O 09/09
Saturn, the sixth planet from the Sun, is home to a vast array ofintriguinganduniquesatellites—53plus9awaitingofficialconfirmation.ChristiaanHuygensdiscoveredthefirstknownmoonofSaturn.Theyearwas1655andthemoonisTitan.Jean-DominiqueCassinimadethenextfourdiscoveries:Iapetus(1671),Rhea(1672),Dione(1684),andTethys(1684).MimasandEnceladuswerebothdiscoveredbyWilliamHerschelin1789.The next two discoveries came at intervals of 50 or more years —Hyperion(1848)andPhoebe(1898).
As telescopic resolving power improved, Saturn’s family of knownmoonsgrew.EpimetheusandJanuswerediscovered in1966.BythetimeCassini–Huygenswaslaunchedin1997,high-resolutionimagingtechniquesusedonEarth-basedtele-scopes had added to the moon count. Cassini has discovered sixmoonsandmayfindmoreduringitsmission.CassinifocusesitscamerasmainlyonobjectsrelativelyclosetoSaturn;thebrightringscomplicatemoon-huntingefforts.Earth-basedtele-scopes focus on the outer part of the Saturn system, and have foundanumberofmoonsintheouterregions.
EachofSaturn’smoonsbearsauniquestory.Twoofthemoonsorbitwithingapsinthemainrings.Some,suchasPrometheusandPandora,interactwithringmaterial,shepherdingtheringinitsorbit.SomesmallmoonsaretrappedinthesameorbitsasTethysorDione.JanusandEpimetheusoccasionallypassclosetoeachother,causingthemtoperiodicallyexchangeorbits.In2006,Cassinifoundevidenceforanewclassof“moonlets”re-siding within Saturn’s rings, sweeping out small gaps in the ring particles.Theremaybeasmanyas10millionmoonletswithinjust one of the rings.
Here’sasamplingofsomeoftheuniqueaspectsofthemoons:
•Titan—At5,150kilometers(3,200miles)across,Titanisthesolar system’s second-largest moon. Titan hides its surface beneathathick,nitrogen-richatmosphere,butCassini’sinstru-ments have revealed that Titan possesses many parallels to Earth—clouds,dunes,mountains,lakes,andrivers.Titan’satmosphereisapproximately95 percent nitrogen with traces of methane.WhileEarth’satmosphereextendsabout60kilome-ters(37miles)intospace,Titan’sextendsnearly600kilometers(10timesthatofEarth’satmosphere)intospace.
•Iapetushasonesideasbrightassnowandonesideasdarkasblackvelvet,withahugeridgerunningaroundmostofitsdark-sideequator.
•PhoebeorbitstheplanetinadirectionoppositethatofSaturn’slarger moons, as do several of the recently discovered moons.
•Mimashasanenormouscraterononeside,theresultofanimpact that nearly split the moon apart.
•Enceladusdisplaysevidenceofactiveicevolcanism:Cassiniobservedwarmfractureswhereevaporatingiceevidentlyes-capes and forms a huge cloud of water vapor over the south pole.
•Hyperionhasanoddflattenedshapeandrotateschaotically,probablyduetoarecentcollision.
•PanorbitswithinthemainringsandhelpssweepmaterialsoutofanarrowspaceknownastheEnckeGap.
•TethyshasahugeriftzonecalledIthacaChasmathatrunsnearly three-quarters of the way around the moon.
•FourmoonsorbitinstableplacesaroundSaturncalledLagran-gianpoints.Theseplaceslie60degreesaheadoforbehindalargermoonandinthesameorbit.TelestoandCalypsooccupythetwoLagrangianpointsofTethysinitsorbit;HeleneandPoly-deucesoccupythecorrespondingLagrangianpointsofDione.
•SixteenofSaturn’smoonskeepthesamefacetowardtheplanetastheyorbit.Called“tidallocking,”thisisthesamephe-nomenonthatkeepsourMoonalwaysfacingtowardEarth.
In addition to studies of Titan, Cassini continues to gather data aboutmanyoftheothersatellitesinanefforttofullyunderstandthe nature, formation, and dynamics of Saturn’s many intriguing moons.
FAST FACTS
•LargestMoonofSaturn Titan Titan’sDiameter 5,150km(3,200mi)
•ClosestMoontoSaturn Pan Pan’sDistancefromSaturn 133,583km(83,022mi)
•FastestOrbit Pan Pan’sOrbitAroundSaturn 13.8hours
•NumberofMoonsDiscoveredbyVoyager 3 (Atlas,Prometheus,andPandora)
•NumberofMoonsDiscoveredbyCassini 6 (Methone,Pallene,Polydeuces,Daphnis,Anthe,andAegaeon)
ABOUT THE IMAGES
1 2 3
4 5
6 7 8
Cassini’1 s visual and infrared mapping spectrometer can view different layers of Titan’s atmosphere simultaneously.
2 Falsecolor(blue)emphasizesicywalls offracturesonEnceladus.
3 TheHerschelcrateronMimasisarelicofalargeimpactthat nearly destroyed this moon.
4 ThisisthelandscapeseenbytheHuygensprobeonitsdescent to the surface of Titan.
A false-color view pr5 ocessed to enhance the individual jets spurting ice particles on Enceladus.
6 ThisimageisamosaicofimagesofPhoebetakenbyCassini during its historic close encounter in June 2004.
This image of Iapetus, the two-toned moon, shows the 7
brighttrailinghemisphere.
Cassini’8 s false-color image of Rhea enhances the slight dif-ferences in natural color across the moon’s face.
FOR MORE INFORMATION
solarsystem.nasa.gov/saturn
ForthemostrecentSaturnmooncount,visit: solarsystem.nasa.gov/planets/profile.cfm?Object= Saturn&Display=Moons
Some of Saturn’s moons are shown at relative distances to the planet.
