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
chris.mckay@nasa.gov
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
CH3Cl
Viking 1 results Biemann et al. 1977
"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."
Biemann et al. 1977 detected a sharp methyl chloride
peak at VL1.
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
bleach
salt
The Cl atom is present on Mars: it molecular form is unknown
except at the Phoenix site, where it is predominately perchlorate
Keller et al. JGR 2006
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)
Mars-like Soils:
The Atacama Desert in Chile is an organic
and microbiological analog of Mars:
Atacama Desert
Mars
•Very low content of organics on surface
•Low recoverable DNA and no CFU
•Presence of abiotic oxidants
Navarro-Gonzalez et al. Science 2003
 Atacama soil
 Atacama soil with
1% perchlorate added
Adding perchlorate:
1. Organics gone
2. NO gone
3. CH3CL and CH2Cl2
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.
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. 2011
Landing: 5 Aug 2012
10:15 pm PDT
Gale Crater
20 km landing ellipse
There is a pyrolysis GCMS on the upcoming MSL mission
Sample Analysis for Mars
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
Two sources of non-biological organic materials:
Meteorites and Miller-Urey synthesis experiments
How do they differ from life?
Two sources of non-biological
Twoorganic
sourcesmaterials:
of non-biological
organic materials:
Life
Miller-Urey Experiments
The building blocks of Earth life.
Could be different for alien life forms.
Lehninger, Biochemistry, 1975 page 21
Concentration
Abiotic organic
Chemistry
Type of molecule
Concentration
Abiotic organic
Chemistry
Concentration
Type of molecule
Biology
Type of molecule
Concentration
Abiotic organic
Chemistry
Concentration
Type of molecule
Biology
Type of molecule
Concentration
Different Biology
Type of molecule
this slide intentionally left banke