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ASTR/GEOL-2040: Search for life in the Universe: Lecture 21

ASTR/GEOL-2040: Search for life in the Universe: Lecture 21. Water on Mars Detection method The eons of Mars. Axel Brandenburg (Office hours: Mondays 2:30 – 3:30 in X590 and Wednesdays 11-12 in D230). Martian life claims: 3 categoroies. Viking 1+2 landers

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ASTR/GEOL-2040: Search for life in the Universe: Lecture 21

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  1. ASTR/GEOL-2040: Search for life in the Universe: Lecture 21 • Water on Mars • Detection method • The eons of Mars Axel Brandenburg (Office hours: Mondays 2:30 – 3:30 in X590 and Wednesdays 11-12 in D230)

  2. Martian life claims: 3 categoroies • Viking 1+2 landers • Microbes in the soil perform metabolism on supplied organics • Methane in martian atmosphere • Methanogenes? • Martian meteorites • Fossil evidence

  3. Martian life claims: 3 categoroies • Viking 1+2 landers • Microbes in the soil perform metabolism on supplied organics • Methane in martian atmosphere • Methanogenes? • Martian meteorites • Fossil evidence

  4. …where has all the water gone? Burns Cliff (Endurace Crater) Layering: shallow ground water Opportunity Dec 2004

  5. Modern topographic map of Mars • xx Opportunity: not even in a deep spot

  6. Dust storm • Predictable • Phoenix observed precipitation • But evaporated before reaching ground 2012 November 18

  7. Detecting water from space • Gamma ray spectrometer • Use ”illumination” by cosmic rays • ”fast” neutrons from collisions • Excite atoms  unique signature • Observed hydrogen • Most of it is in H2O

  8. Dust storm (energy depends on atom) • Predictable • Phoenix observed precipitation • But evaporated before reaching ground (protons) best with water (Proton similar mass) 2012 November 18

  9. Where is presently most of the H2O? • At high latitudes • At mid latitudes • Near the equator

  10. Dust storm • Predictable • Phoenix observed precipitation • But evaporated before reaching ground 2012 November 18

  11. Where is most of the water? • At high latitudes • At mid latitudes • Near the equator

  12. Low latitude H2O patches Elysium, Terra Sabaea, Terra Sirenum(proximity to volcanoes: increased melt) Terra Sabaea 2012 November 18

  13. Valley networks (~4 Gyr old)

  14. outflow channels (~3 Gyr old)

  15. Modern topographic map of Mars • xx

  16. outflow channels are mainly associated with… • Massive events clearly associated with volcanic events Volcanoes!

  17. So what does g ray spectrometer observe? • g rays • fast neutrons • thermal (slow) neutrons

  18. So what does g ray spectrometer observe? • g rays • fast neutrons • thermal (slow) neutrons

  19. Eonson Earth • … • Hadean (3.8 – 4.6 Gyr) • Archean (2.5 – 3.8 Gyr) • Proterozoic (0.55 – 2.5 Gyr) • Phanerozoic

  20. Different eons for Martians • … • Noachian (3.7 – 4.1 Gyr, warm & wet) • Hesperian (3 – 3.7 Gyr, volcanoes, acidic) • Amazonian (0 – 3 Gyr, cold, hyperarid)

  21. What’s different btw the 3 . Noachis Terra Hesperia Planum Terra Sabaea • Craters • Volcanos • Elevation • Latitude

  22. Amazonis Planitia . Terra Sabaea 2012 November 18

  23. Amazonis Planitia . Hesperia Planum = Land to the West Terra Sabaea 2012 November 18

  24. Schiaparelli (1899) • xx

  25. Amazonis Planitia . Hesperia = Land to the West Noachis Terra = Land to the Noah Terra Sabaea 2012 November 18

  26. There can be different ones • … • Phyllocias = phyllosilicates • Theriikian = sulphurous • Siderikan = iron

  27. Sedimentary rock rare • Igneous

  28. Carbonates rare: 2 – 5 wt% • wt% = percentage by weight • Evidence of wet & warm past • Why only 2 – 5 wt% ? • Earth: 10% of sedimentary rocks are limestone • Mars: no time to form? • No: became acidic 3 Gyr ago (sulfate-rich) Lon 272

  29. They got the idea from the Moon • …

  30. Monday • Atmospheric escape • Methane • Meteorites • RGS pp. 109 – 119

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