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SUMMARY:Absence and ambiguity in life’s emergence on the Hadean earth - 
 : Prof Stephen Mojzsis\, Eötvös Loránd University\, Hungary.
DTSTART:20231016T150000Z
DTEND:20231016T160000Z
UID:TALK205129@talks.cam.ac.uk
CONTACT:Dr Emily Mitchell
DESCRIPTION:Silicate+metal+fluid planets like Earth form hot via accretion
 \, differentiation\, and intrinsic radioactive decay. The process of losin
 g heat in such planets sets off a chemical-mechanical cascade wherein meta
 ls (Fe+Ni) form a core\, and silicates partition into a mantle and siliceo
 us crust. The outcome is a rocky surface beneath an outgassed fluid envelo
 pe. 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 prebi
 otic chemistry – hosted diverse hydrothermal systems near (ultra-)magnes
 ian and more silica-rich volcanic centers. Geodynamic motions and differen
 tial buoyancy of this primordial crust also almost certainly means that sc
 attered emergent islands existed which could host chemically varied solid 
 surfaces beneath a dense greenhouse atmosphere bathed by the young Sun. Li
 fe has been on Earth for some four billion years. Pre-biotic conditions fa
 cilitated chemistry which led to biochemistry. We do not know whether the 
 earliest environments were ideally suited for the origin life\, or just go
 od enough. The inferred complexity for even the minimum biological entity 
 probably means that operative and persistent life is the most difficult de
 velopmental stage to reach.
LOCATION:Ryle Seminar Room\, Institute of Astronomy
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