Searching for Silicate Bioweathering

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Searching for Silicate Bioweathering on Earth
and Mars
Martin Fisk, Oregon State University Michael
Storrie-Lombardi, Kinohi Institute contributors Ra
du Popa, Portland State University Olivia Mason,
Oregon State University Ed Vicenzi, Smithsonian
Institution
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Probabilistic Classification of Biotic Alteration
in Basalts
(Sans Expert)
Elemental Abundance Signatures for Abiotic
Biotic Alteration of Ocean Basalts Na, Mg, Al,
Si, P, Cl, K, Ca, Ti, Mn, Fe
PCA
ANN
Storrie-Lombardi, M. C. and Fisk, M. R. (2004)
Elemental abundances in sub-ocean basalt glass
and secondary minerals evidence of biotic and
abiotic alteration Geochem., Geophys., and
Geosys. 5 (10), doi10.1029/2004GC000755.
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Hawaiian HSDP Archaea
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Fisk, M.R, Popa, R., Mason, O.U.,
Storrie-Lombardi, M.C., and Vicenzi, E. 2006,
Iron-Magnesium Silicate Bioweathering on Earth
(and Mars?), Astrobiology, 6 (1), p. 48-68.
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Observations in a Martian Meteorite
Nakhla
Nakhla
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Why Choose an Ancient Igneous Rock Site?

• Provides information on earliest volcanism on the
  planet.
• Provides a record to test the hypothesis of early
  aqueous alteration.
• Igneous rocks preserve evidence of life for
  billions of years.
• Biosignature in igneous rocks can incorporate but
  do not depend on the presence of classical
  organic constituents H, C, O, N, P.
• Biosignatures in igneous rocks are amenable to
  automated pattern recognition techniques.
• Igneous rock sites are dry and comply with
  planetary protection constraints.
• Multiple sites exist (many already well-surveyed)
  exhibiting low altitude, low latitude, minimal
  slope, and minimal wind characteristics.

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Ideal Igneous Site

• Mandatory
• Exposed Noachian igneous rocks.
• Excellent if
• Prolonged exposure to water
• Dry ever since for preservation.
• Ideally
• Go to availability of sulfates and layered
  terrain
• And of course
• Surveyed by MOC, MOLA, TES, THEMIS, HSRC, and
  OMEGA and targeted by MRO/CRISM.
• Optimize engineering constraints for wind,
  altitude, latitude, and slope.

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What Site?
Site Location Altitude Proponent (km)
NE Syrtis Major 10oN 70oE 0.5-1.5 Harvey Nil
i Fossae 22oN 75oE -0.6 Mustard Marwth
Vallis 22.3oN 343.5oE -2 Bibring Eos
Chasma 10.9oS 321.7oE -4.1 Hamilton
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