Lec 11 Life in the Solar System

Gas exchange experiment looks for metabolism detects

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Unformatted text preview: , O2 released! •  O2 required chemical reaction! –  Second mode: wet, nutrients! •  Monitor for 6 months, no further activity! •  No sign of metabolizing, earth-like life! Gas Exchange Experiment! •  Looks for metabolism! •  Detects gaseous products! • Using gas chromatograph! Labeled Release Experiment! •  Assumed metabolizing Martians! –  But less Earth like! –  Simpler mix of nutrients, labeled with 14C! –  Metabolizing organisms produce 14CO2! –  Very sensitive to small amounts! •  Results: immediate release of 14CO2! –  No further release when more added! •  Chemical, not biological, reaction suspected! Labeled Release! •  Looks for metabolism! •  Nutrients labeled with 1 4C ! Pyrolytic Release Experiment (PR)! •  Assumed photosynthesizing autotrophs! –  Adapted to Mars! –  Supply light, Martian atmosphere! –  But label with 14CO2 and 14CO! •  After incubation, remove gases! •  Burn up (pyrolize)! •  Look for 14CO2 from burned-up Martians! –  Interesting Results ! Pyrolytic Release! •  Looks for autotrophs! •  Supplies gases! •  Labeled with 14CO2! Pyrolytic Release Results! •  First experiment gave positive result! –  Could be about 100 to 1000 bacteria! •  Could have escaped detection with GCMS! –  Repeat with sterilized sample (175 C, 3 days)! •  Reaction reduced, but not eliminated! –  Further controls, lower T sterilization! •  Little change in results! •  Conclusion: most likely a chemical reaction! Summary of Viking Results! No organic molecules found! ! Some apparent activity in pyrolytic release expt.! ! Could be photosynthesis by 100 - 1000 bacteria! They could have escaped detection by organic! matter analysis! But, sterilized controls did same thing! ⇒ !chemical, not b...
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This note was uploaded on 04/05/2013 for the course UGS 302 taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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