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ASTR/GEOL-2040: Search for life in the Universe: Lecture 20

Delve into the factors influencing potential life on Mars, including Martian seasons, the Phase diagram of water and carbon dioxide, Viking experiments, and the presence of perchlorates. Understand the challenges of proving Martian life claims and the significance of modern Mars research.

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ASTR/GEOL-2040: Search for life in the Universe: Lecture 20

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  1. ASTR/GEOL-2040: Search for life in the Universe: Lecture 20 • Conditions on Mars • Phase diagram • Life on Mars? Axel Brandenburg (Office hours: Mondays 2:30 – 3:30 in X590 and Wednesdays 11-12 in D230)

  2. This week • Mars, RGS 85-96, Lon 255-288, BS 267-301 • Viking experiments: BS 287-291

  3. Martian seasons • Orbital period • 687 days=1.9 yr • Rotation period • 1d37m22s • Solar day = sol • 1d39m35s Summers/winters in north/south?

  4. Martian seasons

  5. South more extreme • Caps evaporate • 1/3 more CO2 gas • Lots of wind • Dust storm season!

  6. Martian seasons Dust season

  7. Martian weather • Fairly Predictable • Phoenix observed precipitation • But evaporated before reaching ground 1976 Viking 1 orbiter 2008 Phoenix lander

  8. The three phases • Solid • Liquid • Gas

  9. Phase diagram: carbon dioxide • From 1700 K to 20 K • Refractory minerals: T50>1100K

  10. Water vs. carbon dioxide • From 1700 K to 20 K • Refractory minerals: T50>1100K

  11. Phase changes possible • When temperature changes • When pressure changes • When temperature and/or pressure change

  12. Phase diagram of water

  13. Phase changes possible • When temperature changes • When pressure changes • When temperature and/or pressure change

  14. Phase diagram of water

  15. Phase changes possible • When temperature changes • When pressure changes • When temperature and/or pressure change

  16. Modern topographic map of Mars • xx Viking 2 far north; Phoenix even more! Northern planes…

  17. 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

  18. The Viking labs (1976) • Gas chomatograph - mass spectrometer (GCMS) • No organics detected (less than on moon!) • Decisive reason why conclusion: no life

  19. Syrtis Major, Olympus Mons, etc X Viking 2 X Viking 1

  20. Viking results of 1976 • Lots of pictures, not much change • Sometimes winds, condensation, precipitation, clouds

  21. Modern topographic map of Mars • xx

  22. Martian sky • Black (not much air) • Except when dust: brown • Sunsets blue • Blue gets transmitted

  23. The Label Release Experiment • Supply “nutrients” (amino acids, etc) • Control experiment + = CO2+…

  24. Control Experiment • Soil heated to 140 C, later 40 – 50 C • To sterilize soil + = nothing

  25. HW5: working with a paper

  26. Quote from Sagan • … the more extraordinary the claim, the more extraordinarily well-tested the evidence must be. • The person making the extraordinary claim has the burden of proving to the experts at large that his or her belief has more validity than the one almost everyone else accepts…

  27. Phoenix lander discovered perchlorates • Explains why no (not much) organics are found • Might also explain results of Viking Experiments

  28. Perchlorates: KClO4 • Claim for life not generally accepted • But it does remain somewhat puzzling

  29. Next time • Water on Mars • RGS 99 - 109

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