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Mars

Mars. ASTR-3040 Astrobiology Day 19. Homework. Chapter 8 Due Thurs. March 31 3, 7, 13, 23, 30, 32, 41, 46, 51, 52 Plus (49 or 50) if you've read one of the books or seen one of the movies. Search for Life on Mars. Evidence – 3 categories 1. Viking experiments 2. Methane in atmosphere

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Mars

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  1. Mars ASTR-3040 Astrobiology Day 19

  2. Homework • Chapter 8 • Due Thurs. March 31 • 3, 7, 13, 23, 30, 32, 41, 46, 51, 52 • Plus (49 or 50) if you've read one of the books or seen one of the movies.

  3. Search for Life on Mars • Evidence – 3 categories • 1. Viking experiments • 2. Methane in atmosphere • 3. Martian meteorites found on Earth

  4. Viking • Carbon Assimilation Experiment. • Mix soil with CO, CO2, H2O (tagged) to see if incorporated into the soil – would indicate life. • No positive result. • Gas Exchange Experiment • Mix soil with organic broth and look for gas release • No positive result.

  5. Viking • Labeled Release Experiment • Mix soil with organic broth and look for gas release. • Should increase if life was present. • Positive result, and heating stopped it. • Gas Chromatograph/Mass Spectrometer • Look for organic molecules in soil. • No positive result, and sensitivity seems to rule out the results of the LRE.

  6. Viking • Methane on Mars • Mars Express found significant level of methane in atmosphere, cyclic concentration levels. • Comet impacts, volcanoes, or life. • Potential correlation with water vapor location. • But, could be outgassing from volcanic activity. • If warm enough to support this, could also be warm enough to support liquid water underground.

  7. How do we Search for Life? • Mars Reconnaissance Orbiter (2006)‏ • Higher resolution images to map landing sites. • Phoenix (2008) lander to look for ice near poles • and organic material. • Next up: • Mars Science Laboratory (2009 launch) • More sophisticated rovers than Spirit & Opportunity • Sample return mission about 2014 - 2016.

  8. Contamination • Real concern • 1967 treaty requires < 1:1000 chance • Strive to do better than this. • Spacecraft sterilization program. • Sample return mission has a reverse concern. • Think “Andromeda Strain” • Do we use ISS as the quarantine facility?

  9. Humans • Long term goal (2025-2030?)‏ • Shielding is a concern for radiation hazard. • Vast amount of stuff needed for a long mission. • Pro: • Humans can explore better than robots. • Real time decisions, autonomous. • Con: • Serious contamination issue.

  10. Terraforming • Long, expensive process • How increase greenhouse gas concentration? • How increase atmospheric pressure? • How maintain the new atmosphere? • Liquid water? • Ethical issues

  11. Martian Meteorites • 1984 - “Allen Hills” region of Antarctica ALH84001 • 1996 - “fossil evidence” for life on Mars. • Igneous, about 4.5 Gyr old. • Probably on surface when water was present. • Carbonate grains in the rock – 3.9 Gyr old • Formed in water. • Blasted off of Mars about 16 Myrs ago and landed on Earth about 13,000 yrs ago.

  12. Evidence for Life • Carbonate grains – Mg-, Fe-, Ca-rich carbonates • layering caused by life on Earth • PAHs in the carbonate grains • Much higher in ALH84001 than in other meteorites • Produced by decay of dead organisms. • Magnetite crystals in Fe-rich layers of carbonates • On earth, only produced by bacteria • High magnification images show rod-like structures • Nanobacteria? Found on Earth now.

  13. Microscopic chains of magnetite crystals. Top: Earth bacteria; Bottom: ALH84001 Top: Terrestrial nanobacteria from Sicily. Bottom: ALH84001 structures, 100 nm long

  14. Alternate Explanations • Carbonate grains • Pulses of hot water might produce this structure. • PAHs in the carbonate grains • Terrestrial contamination in Antarctica • Magnetite crystals in Fe-rich layers of carbonates • Coincidental? Theoretical ways to form them • Not shown experimentally • High magnification images show rod-like structures • They just look like nanobacteria. • They might be an artifact of slicing the rocks

  15. Summary • We don't really know. • Probably will have to wait until we can actually study rock in situ and bring some back for more detailed analysis.

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