Martians? Life on Mars

1. Martians?Life on Mars ASTR 1420 Lecture 12 Sections 8.1-8.5

2. Fantasies of Martian Civilization • William Herschel (late 1700s) • discoverer of Uranus • discovered polar ice caps of Mars • discovered the length of the Martian day (24h 37 min) • noticed permanent marks on the surface • “… inhabitants probably enjoy a situation in many respects similar to our own!” • Giovanni Schiaparelli (late 1800s) • discovered 79 linear features (“canali”) meaning “channels”, but incorrectly translated as “canals” • Then, Percival Lowell… Ground-based image of Mars

3. Percival Lowell(1855-1916) • He knew that not all astronomers see Schiaparelli’s canals… • He thought that it is due to poor “seeing” Built an observatory in 1894 at Flagstaff, AZ to observe Mars… On top of Mauna Kea Due to the astronomical seeing effect, long exposed pictures get blurry.

4. Lowell’s interpretation of Martian surface • Mapped 200 canals. He knew about Mars being arid and its polar ice caps… • Canals  transportation of water from poles to equator cities… • One global network  a single nation. • But, many scientists did not believe his claim (w/o confirmation). • Excepting a couple of large geometrical features, his canals were purely imaginary! • All scientists abandoned Martian canals (by 1910), but the idea of the advanced Martian civilization persisted among public for a long long time!

5. Martians’ Attack! A famous science fiction written by H. G. Wells, “The War of Worlds”. Orson Welles’s 1938 radio broadcasting… Intro.. Martians start attacking with their thermal beam!

6. Mariner 41965 • Stillon-going debate on the Martian canals and cities in 60s • No canal ! (no hint of advanced civilization)

7. Viking Landers1979 Viking Lander 1 & 2 : 1979 Two landers within two months landed at nearly opposite sites across the planet. And two orbiters… A thin coating of ice on the rocks and soil… Many images over several months… No visible life.

8. “Face on Mars” and other ancient relics… Mars Global Surveyor 1997 “Face on Mars” in 1976 Viking 1 orbiter • When you deal with 100,000 of images, you can always find some odd patterns!

9. Liquid Water from the Underground. August 1999 September 2005

10. Pathfinder + Sojourner1997 • Mars lander, Pathfinder, on July 4, 1997. • Its rover, Sojourner, could travel 10-20m away from the lander.

11. Martian Water Today Mars Odyssey : Hydrogen content of the soil = existence of Water. Bluehighest content…

12. Frozen Sea structure? on Mars on Earth

13. Wet Red Planet!! • NASA's Mars Reconnaissance Orbiter took images of a fresh, 6 meter wide crater on Mars on Oct. 18, 2008, left, and on Jan. 14. The impact exposed water ice from below the surface.

14. Climate History of Mars • We saw evidence of liquid water on the Mars. • Why was Mars warmer and wetter in the past? • If Mars had about 400 times more CO2, then it could have liquid water on the surface via a stronger greenhouse effect and denser atmosphere. • If the composition of outgassed material was the same as Earth’s, then it should have enough H2O to fill oceans hundreds meters deep. • However, the Sun was dimmer in the past  CO2 alone could not have warmed the ancient Mars’ atmosphere high enough… • Possible solutions • enhanced greenhouse effect by other gases such as methane • young Sun was not that dimmer • Mars never had an extended period of warmth  liquid water only after major impacts… • It was never Earth-like, but Mars was certainly warmer and wetter!

15. Where did CO2 go? • Mars lost significant amount of CO2 where did it go? • condensed to polar caps • chemically bound to surface rocks • remain in the atmosphere • lost to space • Why such a change?  mainly due to its small size!!

16. Small size of Mars • Small size • lost internal heat rapidly… • outer core solidified • weakened magnetic field • became vulnerable to solar winds • being stripped off • It is large enough to have volcanism and outgassing in the beginning… • H2O got also dissociated by solar UV radiation: 2H2O  2H2+ O2 • H2 got escaped quickly while O2rusted the rocks and lost to space over time…

17. Short-term climate changes of Mars After losing its atmosphere and H2O, has the climate of Mars unchanged for the past 2-3 Gyr? No. The climate had changed with period of hundreds of thousands years! Ice ages of Earth  due to the change of obliquity. 22° - 25° : small range due to the stabilizing effect of the large Moon Mars does not have a large moon. Closer to Jupiter  a much wider range of obliquity change, 0° - 80° Larger obliquity  warm summer pole  more CO2 stronger greenhouse effect  warmer temperature. Even with this, average T couldn’t maintain surface liquid water, but high enough to have liquid water just beneath the surface!

18. Is Mars habitable? • Mars has • chemical elements • energy  Sun light + chemical energy(?) • Current surface of Mars is not habitable due to no liquid water • However, during the high obliquity periods, Martian surface might have been habitable! • Subsurface has been habitable throughout the period until now. Time to search!

19. Evidence of Life on Mars? • There are some scientific claims already about the existence of life on Mars  on-going debate! • Three groups of claims • based on Viking lander data • fromMartian atmosphere studies • fromMartian meteorites

20. Viking Experiments Examine the soil of Mars to see if there are any living microbes.  Two Viking landers in 1976 Four experiments carbon assimilation experiment gas exchange experiment labeled release experiment gas chromatography

21. 1. Carbon Assimilation Experiment 12C : 98.9% 13C : 1.07% 14C : <10-12 Mix Martian soil with terrestrial CO2 and CO ( with 14C) : if these gases were used by life, then 14C would get incorporated into the soil • Yes! Some 14C were incorporated! • repeated experiments after 3 hours of cooking the soil at 175°C • a hint of 14C assimilation still • Must have been a non-biological process of processing Carbon

22. 2. Gas Exchange Experiment Mix the soil with organic nutrients and check for any released gas (e.g., O2 for terrestrial photosynthesis) • O2 was released! • But, similar result from an experiment with no sunlight!?! • O2 detection even after a thermal treatment of the soil • Non-biological process

23. 3. Labeled release experiment Mix the soil with organic nutrients that were tagged with radioactive 14C and 35S • if nutrients were used by Martian microbes, byproducts containing 14C and 35S would be detected via radioactivity. • Yes, indeed! • Repeated an experiment after cooking the soil at 160°C  then no detection! • Evidence of Life??

24. 4. Mass Spectrometer Measuring the level of organic molecules… This is the one that made most scientists believe that Martian soil does not have microbes… What is this experiment??

25. Martian Meterite : ALH84001, a magnetite? Magnetobacteriamagnetite is known in similar crystals on Earth only when deposited by bacteria ALH84001: a 1.93kg meteorite found in Allan Hills, Antarctica on December 27, 1984

26. ALH84001 : nano-fossils

27. nano-fossils

28. nano-fossils

29. Another microfossil-like structure from ALH84001

30. Is (was) there life? • Occam’s razor?  what’s the verdict? • Need more concrete information  more missions • Phoenix lander (2007 launched, 2008 landing) • Mars Science Laboratory (launched 2011 Nov, arrive in August 2012!!!) • Mars sample return (ESA, Aurora) Prevent contamination !?!

31. Phoenix Lander Highlights • Lander dug up Martian soil • several ice blocks were exposed which were sublimated over 3-4 days “sol” = Martian day = 24 hrs 39min

32. Pheonixlander confirmed water ice

33. In summary… Important Concepts Important Terms Martian canals ALH84001 nano-fossil • Fantasy of Martian Civilization • Characteristics of Mars • Seasons of Mars • Climate history of Mars • Evidences of Water • Reason for Mars climate change • Viking Lander Experiments • Evidence of Life from ALH84001 • Chapter/sections covered in this lecture : 8.1-8.5 • Life on Jovian Moons : next class!!