Redox Chemistry in Large Impacts and the Origin of Life


Wednesday, March 26 2008 - 12:00 pm, PDT
Jay Melosh

All material affected by close proximity to large impacts, for example, tektites and microkrystites, is chemically reduced compared with the starting material. In her PhD research, Abby Sheffer demonstrated that this chemical reduction is the inevitable consequence of the high temperature equilibrium between liquid and gas phases in the hot vapor plume. In parallel work on his PhD, Matt Pasek demonstrated that only the reduced form of Phosphorous can participate in aqueous reactions that lead to the precursors of life. Although Pasek sought the source of this reduced Phosphorous in the relatively rare mineral Schreibersite, I will argue that the conditions for reduction are far more general. In this talk I will discuss the thermodynamic conditions that exist in an impact vapor plume, show how reduction occurs and argue that the principal source of reduced Phosphorous on the early earth was probably material vaporized in large impacts and globally distributed in the fast distal ejecta of large impact events. All life on earth may thus owe its birth to the capacity of large asteroid impacts to perform chemical reduction.

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