Biology
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p43c1448m&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P43C-1448
Biology
[0486] Biogeosciences / Soils/Pedology, [1625] Global Change / Geomorphology And Weathering, [1886] Hydrology / Weathering, [5220] Planetary Sciences: Astrobiology / Hydrothermal Systems And Weathering On Other Planets
Scientific paper
Recent investigations of Pliocene-age paleosols in the Aberdare dip slope of the Eastern Rift Valley of Africa reveal fossilized bacteria and fungi coatings on glassy vesicles of weathered Fe-rich and zeolite phenocrysts mixed with allochothonous grains derived from nearby basement outcrops and aeolian sources. These microbes formed in a dry climate as attested to by clay mineral concentrations that show predominate Ca-smectite, illite-smectite and associated chemical indices. The fossil bacteria and fungi are embedded in clays and secondary Fe accumulations (hematite and goethite), the latter likely assisted with microbe respiratory processes. SEM imagery indicates the presence of sufficiently robust and widely spread colonies of both bacteria and fungi indicative of a dry paleoenvironment, punctuated with short-term humid cycles sufficient for the proliferation of species. Similar paleoenvironments are expected for Mars, such as the water-enriched Tharsis Superplume region, where major pulses of magmatic activity were separated by tremendously long periods of quiescence allowing for paleosol development [1]. Episodic volcanism on Mars, as on the flanks of Mount Kenya, would encase the weathered beds (paleosols) which may contain extant or fossil microbes. Exposures of alternating sequences of sheet lavas (from a major pulse) and paleosols (including clays observed through the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), which may have formed during long-term Tharsis inactivity and water and wind activity including ground water migration) occur in the walls of Valles Marineris [2]. In contrast with these Kenyan pedostratigraphic successions, the lower part of a martian paleosol sequence might be salt enriched, and thus the presence of liquid water could occur during lengthy periods of magmatic quiescence (ice house conditions, cf. Antarctic analogue [3]. In Valles Marineris these materials may occur in places where slumping and landsliding processes have produced exposures reachable by a roving vehicle. [1] Dohm, J.M., et al., 2008. GRS evidence and the possibility of paleooceans on Mars. Journal of Planetary and Space Sciences, doi: 101016/j.pss.2008.10-08. [2] Murchie SL, et al. 2009. A synthesis of Martian aqueous mineralogy after one Mars year of observations from the Mars Reconnaissance Orbiter. Journal of Geophysical Research. Geophys. Res., in press. [2] Mahaney, W.C., et al., 2001. Morphogenesis of Antarctic paleosols: martian analogue, Icarus, 154: 113-130.
Barendregt R. W.
Dohm James
Kim Kab-Jin
Mahaney William C.
Milner Michael W.
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