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EP: Extraterrestrische Physik

EP 14: Leben und Lebensbedingungen ausserhalb der Erde II

EP 14.11: Vortrag

Mittwoch, 22. März 2000, 18:15–18:30, N3110

Igneous Rocks as a Source of Biochemically Relevant Organic Molecules and of Hydrogen — •Friedemann Freund, Alka Gupta, and Michele Cash — NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035-1000, USA

The search for the origins of Life becomes more and more bewildering. How it all started over 3.5 Gyrs ago still evades comprehension, and how microbial communities can thrive today kilometers below the surface of the Earth also remains enigmatic. Rocks may have played an important role, both in the orgin of Life and its sustenance. Undisputedly, when rocks solidify in H₂O/CO/CO₂/N₂-laden environments, their common silicate minerals form dilute solid solutions with gas/fluid components. H₂O is known to form hydroxy anions, O₃X-OH (X = Si⁴⁺,Al³⁺), but hydroxy pairs, O₃X-OH HO-XO₃, undergo a unique in situ redox conversion: they convert to H₂ plus peroxy, O₃X-OO-XO₃. While the peroxy is tied into the structure, the H₂ is diffusively mobile. Solute CO₂ and solute N₂ appear to undergo the same type of redox conversion, forming reduced carboxy anions (such as formiate) and reduced nitroxy anions, respectively, plus peroxy. Next, as the rocks cool as part of their geological cycle, the low-z elements H, C and N segregate and precipitate at dislocations and other major defects. There they form moieties of the general form [C_xH_yO_zN_w]ⁿ⁻. Upon weathering, these moieties turn into complex organic molecules. Additionally, the H₂ represents a potentially large source of gaseous hydrogen in crustal rocks today that could provide an energy source for deep microbial communities.