The Late Veneer and Earth's habitability - Norm Sleep(SETI Talks 2017)
Δημοσιεύτηκε στις 13 Ιαν 2017
Asteroid
impacts were a hazard to any life on the Hadean Earth. A traditional
approach to geochemical models of the asteroid impactors uses the
concentration of highly siderophile elements including the Pt-group in
the silicate Earth. These elements occur in roughly chondritic relative
ratios, but with absolute concentrations less than 1% chondrite. This
veneer component implies addition of chondrite-like material with
0.3-0.7% mass of the Earth’s mantle or an equivalent planet-wide
thickness of 5-20 km. The veneer thickness, 200-300 m, within the lunar
crust and mantle is much less. The accretion of a large number of small
bodies would provide comparable thicknesses to both bodies, as the
effect of gravity is modest.
impacts were a hazard to any life on the Hadean Earth. A traditional
approach to geochemical models of the asteroid impactors uses the
concentration of highly siderophile elements including the Pt-group in
the silicate Earth. These elements occur in roughly chondritic relative
ratios, but with absolute concentrations less than 1% chondrite. This
veneer component implies addition of chondrite-like material with
0.3-0.7% mass of the Earth’s mantle or an equivalent planet-wide
thickness of 5-20 km. The veneer thickness, 200-300 m, within the lunar
crust and mantle is much less. The accretion of a large number of small
bodies would provide comparable thicknesses to both bodies, as the
effect of gravity is modest.
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ANAΡΤΗΣΗ ΑΠΟ ΤΟ YOUTUBE 14/4/2017
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