Absence and ambiguity in life’s emergence on the Hadean earth

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• : Prof Stephen Mojzsis, Eötvös Loránd University, Hungary.
• Monday 16 October 2023, 16:00-17:00
• Ryle Seminar Room, Institute of Astronomy.

If you have a question about this talk, please contact Dr Emily Mitchell.

Silicate+metal+fluid planets like Earth form hot via accretion, differentiation, and intrinsic radioactive decay. The process of losing heat in such planets sets off a chemical-mechanical cascade wherein metals (Fe+Ni) form a core, and silicates partition into a mantle and siliceous crust. The outcome is a rocky surface beneath an outgassed fluid envelope. In the first 500 Myr (q.v. Hadean eon) the Earth’s primordial crust existed with liquid water. It was molded by volcanism and affected by late accretion bombardment. This early crust – the latent template for prebiotic chemistry – hosted diverse hydrothermal systems near (ultra-)magnesian and more silica-rich volcanic centers. Geodynamic motions and differential buoyancy of this primordial crust also almost certainly means that scattered emergent islands existed which could host chemically varied solid surfaces beneath a dense greenhouse atmosphere bathed by the young Sun. Life has been on Earth for some four billion years. Pre-biotic conditions facilitated chemistry which led to biochemistry. We do not know whether the earliest environments were ideally suited for the origin life, or just good enough. The inferred complexity for even the minimum biological entity probably means that operative and persistent life is the most difficult developmental stage to reach.

This talk is part of the LCLU Seminars series.

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