Life in the Outer Solar SystemJupiterBig R = 11RMassive M = 300 M = 2.5 all the restMostly H2, He Thick AtmosphereBut 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– SurfaceCASSINISPACECRAFT2005 Saturn Tour Highlights:• Jan. 14, 2005: The European Space Agency's Huygens probedescends through Titan's cloudy atmosphere, touching down onthe surface about two and half hours later. Cassini will send thedata back to Earth.• Feb. 15, 2005: Cassini makes another pass by Titan. In 2005,the spacecraft will have six chances to study Titan at altitudesranging from 1,025 kilometers (637 miles) to 60,000 kilometers(37,290 miles).• Mar. 9, 2005: Cassini flies within 500 kilometers (311 miles) oficy Enceladus. Cassini will visit Enceladus five times in 2005.• Sep. 26, 2005: Cassini studies Hyperion at a range of 1,010kilometers (628 miles), the closest approach ever to the tinymoon. It will be Cassini's only visit to the moon during theprimary mission.• Oct. 11, 2005: Cassini turns its instruments on Dione from adistance of 500 kilometers (311 miles).• Nov. 26, 2005: Cassini passes within 500 kilometers (311miles) of Rhea.Huygens Probe• Released from Cassini• Slowed by heat shield• Parachute deploys• Goal of 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?From 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.How 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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