Titan: The moon with an atmosphereThe Saturnian SystemThe story of Titan’s discoverySlide 4Comparison with other solar system objectsSlide 6Titan’s atmosphereTitan’s atmospheric chemistryTholinsResults from VoyagerSurface compositionComparison of surface materialsSlide 13Internal structureTitan’s Formation SequenceCassini-Huygens missionSurface map of TitanSlide 18Slide 19Slide 20Active surface processesFluvial erosionAeolian activitySlide 24Slide 25CryovolcanismSlide 27Slide 28Probable cryovolcanic sitesTitan’s Land-o-Lakes!Slide 31Slide 32Temporal evolution of lakes at South PoleTectonics on TitanSlide 35Clouds on TitanPossibility of life on TitanUnanswered questions about TitanFuture MissionsSlide 40Titan: The moon with an Titan: The moon with an atmosphereatmosphereThe Saturnian SystemThe Saturnian SystemThe story of Titan’s discoveryThe story of Titan’s discoveryDiscovered in 1655 by Dutch scientist Discovered in 1655 by Dutch scientist Christiaan HuygensChristiaan HuygensReferred to it as Referred to it as Luna SaturniLuna Saturni (Saturn's moon)(Saturn's moon) Named ‘Titan’ Named ‘Titan’ in in 1847 by the 1847 by the English astronomer English astronomer John Herschel John Herschel Aerial telescopePossibility of atmosphere suggested by Comas Solas in 1903 , after Possibility of atmosphere suggested by Comas Solas in 1903 , after observing limb darkeningobserving limb darkening Existence of atmosphere confirmed by Existence of atmosphere confirmed by Kuiper in 1944, methane identified in Kuiper in 1944, methane identified in Titan spectrumTitan spectrum Ground-based telescopic observationsGround-based telescopic observations Voyager1 (1980-81) saw featureless surface Voyager1 (1980-81) saw featureless surface Cassini-Huygens mission (1997-present)Cassini-Huygens mission (1997-present)Comparison with other solar system objectsComparison with other solar system objectsLargest satellite of SaturnLargest satellite of SaturnLarger than Mercury and PlutoLarger than Mercury and PlutoSecond largest natural satellite in the solar system after Second largest natural satellite in the solar system after Ganymede Ganymede Similar in size, mass to Ganymede ,CallistoSimilar in size, mass to Ganymede ,CallistoWhy does Titan have an atmosphere , while its Jovian Why does Titan have an atmosphere , while its Jovian cousins don’t?cousins don’t?Titan’s atmosphereTitan’s atmosphereOnly moon in the solar system to possess a Only moon in the solar system to possess a dense atmospheredense atmosphere10 times thicker than Earth’s atmosphere10 times thicker than Earth’s atmospherePresence of huge atmosphere unexplainedPresence of huge atmosphere unexplainedNN2 2 : Major constituent of both Earth’s : Major constituent of both Earth’s and Titan’s atmosphere (~98.4% Nand Titan’s atmosphere (~98.4% N22,, ~1.6% CH~1.6% CH44)) Unique atmospheric organic chemistryUnique atmospheric organic chemistry→ → forms thick haze which envelopes the forms thick haze which envelopes the moon; prevents from seeing the moon; prevents from seeing the surfacesurfaceEarly Earth/Pre-biotic Earth in Early Earth/Pre-biotic Earth in deep freezedeep freezeTitan’s atmospheric chemistryTitan’s atmospheric chemistry 2CH2CH44 →→ C C22HH66 + H + H22 ( (↑)↑)Methane → Ethane + HydrogenMethane → Ethane + HydrogenTholinsTholinsTerm first proposed by Carl Sagan et al.Term first proposed by Carl Sagan et al.Haze made of long chain molecules- ‘tholins’Haze made of long chain molecules- ‘tholins’Solid end products of photolysis and electronic discharge Solid end products of photolysis and electronic discharge experiments simulating other planetary atmospheresexperiments simulating other planetary atmospheresComplex reddish or brownish organic compoundsComplex reddish or brownish organic compoundsNot precise qualification of the compounds constituting Not precise qualification of the compounds constituting Titan’s hazeTitan’s hazeResults from VoyagerResults from VoyagerSaw an orange, featureless ballSaw an orange, featureless ballAtmospheric structure, Atmospheric structure, compositioncompositionPressure-temperature profile Pressure-temperature profile through the atmospherethrough the atmosphere Radio Radio occultation used occultation used to determine to determine Titan’s radiusTitan’s radiusSurface compositionSurface compositionNo conclusive results yetNo conclusive results yetHowever, surface has to be made mainly of water ice (ground-However, surface has to be made mainly of water ice (ground-based/spacecraft observations) based/spacecraft observations) Expected to be coated with hydrocarbons that rain down from Expected to be coated with hydrocarbons that rain down from above (ethane, benzene, propane, etc.)above (ethane, benzene, propane, etc.)Comparison of surface materialsComparison of surface materialsBedrockBedrockSilica Silica Water iceWater iceWorking fluidWorking fluidWater Water MethaneMethaneSediment/SoilSediment/SoilQuartzQuartzWater ice/organic Water ice/organic materials materials (tholins)(tholins)Earth TitanWater cycle on EarthMethane cycle on TitanInternal structureInternal structureMean density of ~1880 kg mMean density of ~1880 kg m-3-3Implies a 50-50 mixture of rock and ice (like Ganymede)Implies a 50-50 mixture of rock and ice (like Ganymede)Sub-surface ocean ?(suggested by Cassini mission results)Sub-surface ocean ?(suggested by Cassini mission results)Titan’s Formation SequenceTitan’s Formation Sequence Titan accretes Titan accretes Core overturn Core overturn occursoccurs Three episodes Three episodes of CHof CH4 4 outgassingoutgassing High pressure High pressure ices form at core-ices form at core- mantle boundarymantle boundary Ice I shell forms Ice I shell forms under methane under methane clathrate layerclathrate layerTobie et al., 2006Cassini-Huygens missionCassini-Huygens missionInternational collaboration between three space agencies International collaboration between three space agencies : NASA, ESA, Italian Space Agency: NASA, ESA, Italian Space Agency2 main elements: Cassini orbiter and Huygens probe2 main elements: Cassini orbiter and Huygens
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