Boreskov

OP‐23present as Fe 0 , Fe +2 , and Fe +3 reflecting complex redox processes in the vapor. The mainrock‐forming element, silicon, also had complex redox behavior forming Si 0 , Si +2 , and Si +4states (Yakovlev et al., 1993). Many chemically active gasses had low life time and rapidlydissipated due to reactions from the atmosphere after their release providing primordialatmosphere composed of stable gases (N 2 , CO 2 , etc.). A noticeable amount of organicmolecules is synthesized in impact‐generated plume including aliphatic hydrocarbons,polycyclic aromatic hydrocarbons (PAH), carbonyl compounds and unsaturated fatty acids,kerogens (Gerasimov and Safonova, 2008).The amount of released water exceeded the volume of modern terrestrial ocean(Gerasimov et al., 1985). Different models give various fate of the primordial ocean fromrunaway greenhouse huge steam atmosphere to moderate temperature water ocean.An important output of the impact‐induced processing of siliceous material of the planetwas formation of the protocrust. The mechanism of its formation was based on theseparation of elements between melt and vapor phases. Volatile elements are convertedinto the vapor plume by secondary impacts more easily and from larger target volume thanrefractory portion of the mixture. Plume condensates could be concentrated in the upperplanetary layer to form protocrust. Concentration of volatile components in the upperplanetary layer resulted in decrease of sink of atmospheric gases and water into the regolithwhat provided stabilization of atmosphere and ocean at the earliest stages of planetaryevolution.Acknowledgment: This research was supported by Russian Academy of Science program P‐25.References[1]. Gerasimov, M.V. and Safonova, E.N. (2008) In: Problems of life origin and evolution. Ed. E.M. Galimov, p145‐153, URSS, Moscow.[2]. Gerasimov, M.V., Mukhin, L.M., Dikov, Yu. P., Rekharsky, V.I (1985) Vestnik of Academy of Science of theUSSR, , № 9, р. 10‐25.[3]. Gerasimov M.V. (2002) In: Catastrophic Events and Mass Extinctions: Impacts and Beyond, Koeberl, C., andMacLeod, K.G., eds., Boulder, Colorado, Geological Society of America Special Paper No 356, pp. 705‐716.[4]. Mukhin, L.M., Gerasimov, M.V., Safonova, E.N. (1989) Nature, vol. 340, pp. 46‐48.[5]. Schidlowski M. (1993) In: The Chemistry of Life's Origins, Eds. J.M.Greenberg et al., Kluwer AcademicPublishers, 389‐414.[6]. Yakovlev, O.I. et al., (1993) Geochemistry International, 30, No 7, 1‐10.69