the search for organics on mars with the mars science laboratory “curiosity”: the next mission...
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The search for organics on Mars with the Mars Science
Laboratory “Curiosity”: the next mission to Mars
12 April 2012
Chris McKayNASA Ames Research Center
VikingonMars:
Life & organics
Viking
• The three Biology Experiments sought to detect life.
• The GCMS sought to detect and characterize organic molecules.
The Viking Biology Experiments
Biemann et al. 1977 detected a sharp methyl chloride peak at VL1.
CH3Cl
"The methyl chloride, or part of it, could conceivably be indigenous to Mars. However, if it were, one would expect that other related compounds like ethyl chloride or methyl bromide would also be formed, but none were detected."
Viking 1 results Biemann et al. 1977
Biemann et al. 1997 reported detection of 8 “contaminants” at VL2 but one of them (methlyene chloride) was not detected in flight blanks and is the expected result of perchlorate and organics heated to high temperature.
There should be organics on Mars
• From meteorites
• From any early biology
Phoenix Mission to Mars May 2008 to Nov 2008
Unexpected Phoenix results
Soil pH ~8
Carbonates 3-5%
Perchlorate 0.5%
Segregated ice No organics
No nitrates } Instrument failures
bleachsalt
Keller et al. JGR 2006
The Cl atom is present on Mars: it molecular form is unknown except at the Phoenix site, where it is predominately perchlorate
Perchlorates on Mars•Perhclorates decomposeand release oxygen whenheated to ~350ºC- used in rockets- destroys organics- produces organo-chlorides
•Strong anti-freeze (-70ºC)- allow liquid on Mars today
•Consumed by microorganisms- terminal electron acceptor ≈ nitrate
•Bad for humans (drinking water limit in California is 6 ppb; Mars is 5,000,000 ppb)
Atacama Desert Mars
•Very low content of organics on surface•Low recoverable DNA and no CFU•Presence of abiotic oxidants
Mars-like Soils:The Atacama Desert in Chile is an organic
and microbiological analog of Mars:
Navarro-Gonzalez et al. Science 2003
Navarro-Gonzalez, R., E. Vargas, J. de la Rosa, A. C. Raga, and C. P. McKay (2010),Reanalysis of the Viking results suggests perchlorate and organics at mid-latitudes on Mars,J. Geophys. Res., doi:10.1029/2010JE003599.
Atacama soil
Atacama soil with 1% perchlorate added
Adding perchlorate:1. Organics gone2. NO gone3. CH3CL and CH2Cl2
Organics on Mars•Everything we thought we knew about organics on Mars from the Viking pyrolysis GCMS is likely wrong
•Instead of an upper limit of ~ ppb, detection (by destruction) at ~ ppm
•Good news for future missions: organics might be high.
•Bad news for future missions: need non-thermal methods
The next mission to Mars:Mars Science Laboratory
Launched: Nov. 2011Landing: 5 Aug 201210:15 pm PDT
Gale Crater
20 km landing ellipse
1. Combustion with O2 to CO2
2. Liquid extraction, SAM will wash the samples with two derivatization agents: tetramethylammonium hydroxide &N-Methyl-N-(Tert-Butyldimethylsilyl) trifluoroacetamide
3. Head space monitoring during pyrolysis
There is a pyrolysis GCMS on the upcoming MSL mission
Sample Analysis for Mars
Two sources of non-biological organic materials:Meteorites and Miller-Urey synthesis experimentsHow do they differ from life?
Two sources of non-biological organic materials:
Life
Miller-Urey Experiments
Two sources of non-biological organic materials:
Lehninger, Biochemistry, 1975 page 21
The building blocks of Earth life.Could be different for alien life forms.
Type of molecule
Co
nce
ntra
tion
Abiotic organicChemistry
Type of molecule
Co
nce
ntra
tion
Abiotic organicChemistry
Type of molecule
Co
nce
ntra
tion
Biology
Type of molecule
Co
nce
ntra
tion
Abiotic organicChemistry
Type of molecule
Co
nce
ntra
tion
Biology
Type of molecule
Co
nce
ntra
tion
Different Biology
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