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Organics on Titan, Water on Enceladus: Worlds of possibilities for life

Organics on Titan, Water on Enceladus: Worlds of possibilities for life. Chris McKay NASA Ames Research Center cmckay@mail.arc.nasa.gov This talk is a compilation based on the work of many colleagues over many years. My thanks and acknowledgements to all of them.

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Organics on Titan, Water on Enceladus: Worlds of possibilities for life

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  1. Organics on Titan, Water on Enceladus: Worlds of possibilities for life Chris McKay NASA Ames Research Center cmckay@mail.arc.nasa.gov This talk is a compilation based on the work of many colleagues over many years. My thanks and acknowledgements to all of them.

  2. Why is Life on other Worlds Interesting? • The possibility of a second genesis of life: comparative biochemistry life is common in the universe (yeah!) • Information about the early planetary environment • Relevant to the origin of life on Earth

  3. Jets of H2O on Enceladus

  4. Given liquid water on Enceladus is there: a plausible origin of life? a plausible ecology?

  5. OK for Enceladus OK for Enceladus Davis & McKay, Origins Life Evol. Biosph. 26, 61-73, 1996.

  6. Plausible Ecologies • The known laws of physicsenergy from thermal gradients, electric fields, radiation • My favorite “extremophile” D. radioduransradiation resistance, salt tolerance, etc. • Actual ecosystems actual microbial ecosystems that require no light & no O2

  7. Examples of ecologically isolated microbial ecosystems (no O2, no light, no organic input) Only three examples are known: Two are are based on H2 from rock reactions(H2 + CO2 CH4 + H2O) • Stevens, T.O. and J.P. McKinley 1995. Lithoautotrophic microbial ecosystems in deep basalt aquifers, Science 270, 450-454. • Chapelle, F.H., K. O'Neill, P.M. Bradley, B.A. Methe, S.A. Ciufo, L.L. Knobel, and D.R. Lovley 2002. A hydrogen-based subsurface microbial community dominated by methanogens, Nature 415, 312-315. One based on radioactive decay • Lin, L.-H., et al. 2006. Long-Term Sustainability of a High-Energy, Low-Diversity Crustal Biome, Science 314, 479-482

  8. H2O FeS2 Geochemical Reactions Radiolysis 4H2 + H+ + SO42- -----> H2S + 2H2O + 2OH- O2, H2O2 H2 SRB Desulfoprofundis tokoloshe Lin et al. 2006, slide courtesy of T. Kieft

  9. Ice Cover Liquid Water Biology: H2 + CO2 CH4 + H2O H2 CH4 Thermal processing, T>500oC: CH4+H2O  H2 + CO2

  10. Stardust flys through the Plume of Enceladus for a Sample Return Mission

  11. If we find organic material in the plume of Enceladus (or Europa & Mars) how can we tell if it was ever alive?If its like us then easy, less interestingIf its alien then hard, but interesting

  12. Abiotic distributions are smooth Biotic distributions are spiked McKay 2004 PLoS Biol 2(9)1260-12623

  13. Abiotic distributions are smooth Biotic distributions are spiked alien McKay 2004 PLoS Biol 2(9)1260-12623

  14. Possibilities for Widespread Life on Titan EarthTitan Carbon basedCarbon based Liquid H2OLiquid CH4 Widespread ??

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