Biosignatures Preservation Potential and Habitability in Phyllosilicates vs. Iron-rich Environments

Details Biosignatures Preservation Potential and Habitability in Phyllosilicates vs. Iron-rich Environments Biosignatures Preservation Potential and Habitability in Phyllosilicates vs. Iron-rich Environments

Dec 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p51a1398b&link_type=abstract

American Geophysical Union, Fall Meeting 2008, abstract #P51A-1398

Biology

0406 Astrobiology And Extraterrestrial Materials, 0424 Biosignatures And Proxies, 0463 Microbe/Mineral Interactions, 3617 Alteration And Weathering Processes (1039), 6225 Mars

Scientific paper

Phyllosilicates have been identified on the surface of Mars by the OMEGA-Mars/Express [e.g., 1], the Mars Reconnaissance Orbiter (MRO) instruments, i.e., HiRISE and CRISM, as well as inferred from rover observations in Gusev Crater [2]). A better understanding of the preservation potential and habitability in phyllosilicates and hematite-rich materials, achieved by studying analog sites, will therefore provide critical information in support of next decade missions landing site selection e.g., 2009 Mars Science Laboratory (MSL), the ESA Pasteur ExoMars. We present geochemical (d13C-org, d13N-tot, CN ratios) and microbiological proxies i.e., Adenosin-Triphosphate (ATP-based) and Limulus-Amebocite-Lysate (LAL-based biomass) from a suite of phyllosilicate and iron-rich environmental samples e.g., Rio Tinto (Spain), Death Valley (CA, USA), Atacama Desert (Chile), and the California coast. Phyllosilicates-rich zones (47-74wt.%) from the Rio Tinto (RT) region can preserve up to 10-time higher amount of organics (C-org = 0.23 wt.%) than the embedding hematite/goethite-rich (34-89 wt.%) rocks i.e., C-org: ~0.05 wt.% [4]. It is possible that under low pH and highly oxidizing conditions [e.g., 3] surface-derived organics are rapidly oxidized within the shallow hematite/goethite-rich materials, but preserved in phyllosilicates (smectites/illite) where conditions are more conducive [4]. ATP-based biomass was detected in some oxidized-rock samples where roots materials were present (750-1245 RLUs). Geochemical and microbiological analyses are underway to confirm the preservation/ habitability trends observed in the Rio Tinto near surface. Preliminary results suggest that oxidized, goethite-rich, sandstone (Purisima formation, CA) have higher ATP- and LAL-based (Gram negative) biomass contents i.e., 2.0 107 cell/g (35.05 EU/mL) and 3891 RLUs, than the overlying clays units i.e., 1.34 107 cell/g (22.0EU/mL) and 1143 RLUs. REFERENCES: [1] Bibring et al., 2006, Science 312:400-404; [2] Wang et al., 2006 JGR E02S16 Vol. 111; [3] Sumner, 2004, JGR, 109; [4] Bonaccorsi and Stoker, Astrobiology 2008; in press.

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