The search for organics on Mars with the Mars Science Laboratory “Curiosity”: the next mission to Mars 12 April 2012 Chris McKay NASA Ames Research Center

Viking on Mars: 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 detected a sharp methyl chloride peak at VL1. CH 3 Cl "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 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

bleach salt

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 decompose and release oxygen when heated 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 DesertMars 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: /2010JE  Atacama soil  Atacama soil with 1% perchlorate added Adding perchlorate: 1.Organics gone 2.NO gone 3.CH 3 CL and CH 2 Cl 2

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 Landing: 5 Aug :15 pm PDT

Gale Crater 20 km landing ellipse

1.Combustion with O 2 to CO 2 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 experiments How 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 Concentration Abiotic organic Chemistry

Type of molecule Concentration Abiotic organic Chemistry Type of molecule Concentration Biology

Type of molecule Concentration Abiotic organic Chemistry Type of molecule Concentration Biology Type of molecule Concentration Different Biology

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