Life in the Outer Solar SystemJupiterBig R = 11RMassive M = 300 M = 2.5 all the restThick AtmosphereMostly H2, HeBut also more complex moleculesColors, stormsLike Miller - Urey⊕⊕Life in Jupiter Atmosphere?Sagan-Salpeter, etc.Sinkers (Plankton)Floaters (Fish)Hunters (Fish)Galileo Results on JupiterReached Jupiter Dec. 1995 Sent probe into Jupiter’satmosphere at 100,000 mile/hourDecelerated at 230 g Lasted for 57 min.Found: Strong windsTurbulence, little lightningSurprise: Little or no H2OMay have entered in an unusualplace (fewer clouds)Life less likely?Europa (Moon of Jupiter)Close-up of “ice floes”Surface: Fractured IceSubsurface Oceans?(Heated from Inside)Galileo - Jupiter’s Moonshttp://www.jpl.nasa.gov/galileo/index.htmlEuropa has a (THIN!) atmosphereH2OHHOUVHO=OThin O2 ATMPressure ~ 10–11 EarthMore evidence for resurfacing along cracks by“ice geysers” fluid ice or liquid waterOrganic molecules on Callisto & Ganymede, maybe Europa?Saturn• Big (9.4 R⊕)• Massive (95 M⊕)• Year 29.5 years• Day 0.43 days• Composition similar toJupiterTitan• Moon of Saturn• Diameter ~0.4 Earth• Atmospheric Pressure = 1.5 × Earth• 85% Nitrogen BUT• Cold (~90 K)• Reducing atmosphere• Haze• Lab for prebiotic chemistryThe Cassini-Huygens Mission• Launched 10/13/97• Arrived Saturn 7/2004• Cassini studies– Saturn– Moons• Huygens– Dropped onto Titan– Study atmosphere– SurfaceCASSINISPACECRAFTHuygens Probe• Released from Cassini• Slowed by heat shield• Parachute deploys• Soft landing• Sample gases in atm.• Results so far:– High winds– 430 km/hr at 120 kmTitan Surface 10km up• Mosaic of images• Taken during descent• Clearly shows featuresPhoto: ESATitan• River channel• Coastline• Liquid is present• Methane (CH4)Photo: ESAWater Rift and Methane Springs?• Straight feature:• Water ice extruded?• Stubby channels:• Methane springs?Lakes at northern latitudes• Radar mapping of northern latitudes (2006)• Strong evidence for liquid lakes• And big cloud of ethane (C2H6)• Ethane raining (or snowing) into lakesLakes and IslandsImage from Feb. 2007: based on radar.Large lake and island (size of Big Island, Hawaii)And smaller lakesFrom the surface of Titan• First view of surface• “Rocks” of water ice– Pebble size (15 cm)• Surface yielding• Mixture of ices– Water– hydrocarbonsMore Titan Results• Hints of ammonia (NH3)/water (H2O) ocean– Under surface– Outgassing of NH3 may supply N2 atm.Lots of stuff on websites• http://saturn.jpl.nasa.gov/home/index.cfm• http://www.esa.int/SPECIALS/Cassini-Huygens/Enceladus• Moon of Saturn• Very shiny• Part of surface old(craters)• Part is new, with cracks• Cassini saw ice geysers(2006)• Subsurface liquid water• Source of heat unclearHow to search for lifeHave to decide what test indicates lifeHard to anticipate conditions (recall Viking results)What about finding “protolife”?National Academy report - how to search for life1. Delivery by comets, meteorites e.g. Mars meteorites2. Sample return - Mars possible3. Experiments by landers -Viking on Mars, …Future: Europa probe and return? Titan?Issues of contamination4. BiomarkersPresence of both O2 and CH4 in Earth atmosphereindicative of lifeHow convincing?Detecting Life on Earth from SpaceGalileo used during close Earth approachPhotographs (1 km resolution) No clear signs of intelligent lifeSpectrometers - evidence of life Lots of O2TPF ConceptsTPF-C Visible light coronagraph (2014?)TPF-I Infrared Interferometer (2020?)Spectroscopy of
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