Martians? Life on Mars. ASTR 1420 Lecture 13 Chapter 8. Mars. Northern low land and southern mountains impact origin?. Geography of Mars. Olympus Mons = tallest mountain in the Solar System!. We saw evidence of liquid water on the Mars!. Climate History of Mars.
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Martians?Life on Mars
liquid water only after major impacts…
Mars was never Earth-like, but it was certainly warmer and wetter!
Current obliquity of Mars = 25.19°
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 and closer to Jupiter a much wider range of obliquity change, 0° - 80°
Larger obliquity warm summer pole more CO2 sublimation stronger greenhouse effect warmer temperature.
Even with this increased seasonal enhanced greenhouse effect, average T cannot maintain surface liquid water, but high enough to have liquid water just beneath the surface!
Time to search!
Examine the soil of Mars to see if there are any living microbes.
Two Viking landers in 1976
carbon assimilation experiment
gas exchange experiment
labeled release experiment
A device that separates vapor components chemically via a gas chromatograph and then feeds the result into a mass spectrometer, which measures the molecular weight of each chemical it can separate, identify, and quantify a large number of different chemicals.
However, the GCMS measured no significant amount of organic molecules in the Martian soil. In fact, Martian soils were found to contain less carbon than lifeless lunar soils returned by the Apollo program.
Mix the soil with organic nutrients and check for any released gas (e.g., O2 for terrestrial photosynthesis)
Asample of Martian soil was inoculated with a drop of very dilute aqueous nutrient solution. The nutrients (7 molecules that were Miller-Urey products) were tagged with radioactive 14C.
Could Martian microbial life forms make a positive LR result and yet showed no traceable amount of organic molecules??
Mix Martian soil with terrestrial CO2 and CO (14C) : if these gases were used by life, then 14C would get incorporated into the soil
The amount of carbon fixed is small by terrestrial standards; highest yields were observed in the light, but some dark activity was also detected; and heating the surface material to 90°C for nearly 2 hours had no effect on the reaction, but heating to 175°C for 3 hours reduced it by nearly 90%.
ALH84001: a 1.93kg meteorite found in Allan Hills, Antarctica on December 27, 1984
Magnetobacteriamagnetite is known in similar crystals on Earth only when deposited by bacteria
Top: macroscopic chain of magnetite crystals produced by bacteria on Earth.
Bottom: Similar chain found in ALH84001
These are smaller than it was thought free-living terrestrial organisms could be, an objection that has shrunk with the study of nano-bacteria.
electron micrographs showing tiny structures that look remarkably like microorganisms or microfossils.
Methane on Earth
Methane detected from observations made by NASA IRTF and Keck telescopes (2003)
Destruction of CH4
Replenishment of CH4