Eisen-liebende Elemente auf Vesta belegen 'späte Akkretion' auf Planetesimalen

[karmaka]

Hoch eisen-liebende Elemente in Vestas Mantel belegen 'späte Akkretion' auf  Planetesimalen

Hoch eisen-liebende (siderophile) Elemente (u.a. Gold, Kohlenstoff, Iridium und Nickel) in Vestas Mantel legen nahe, dass sie durch Meteoriteneinschläge im Prozeß
einer 'späten Akkretion', nach einer bereits vollzogenen Kernbildung, aber vor dem 'großen Bombardement'
angereichert wurden.
Damit fand dieser Prozeß nicht nur auf Erde, Mond und Mars statt, sondern auch auf den frühen Planetesimalen,
deren Akkretion wohl länger dauerte als bisher angenommen.

http://www.livescience.com/19513-early-asteroids-bombardment-impacts.html

automatisierte Übersetzung:

http://translate.google.de/translate?sl=en&tl=de&js=n&prev=_t&hl=de&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.livescience.com%2F19513-early-asteroids-bombardment-impacts.html

Late Accretion on the Earliest Planetesimals Revealed by the Highly Siderophile Elements

Christopher W. Dale, Kevin W. Burton, Richard C. Greenwood, Abdelmouhcine Gannoun, Jonathan Wade,
Bernard J. Wood, D. Graham Pearson

Science 6 April 2012:
Vol. 336 no. 6077 pp. 72-75

http://www.sciencemag.org/content/336/6077/72.abstract?sid=6b4a0b12-a247-4d07-93e1-d05280b970cb

Late accretion of primitive chondritic material to Earth, the Moon, and Mars, after core formation had ceased, can account for the absolute and relative abundances of highly siderophile elements (HSEs) in their silicate mantles. Here we show that smaller planetesimals also possess elevated HSE abundances in chondritic proportions. This demonstrates that late addition of chondritic material was a common feature of all differentiated planets and planetesimals, irrespective of when they accreted; occurring ≤5 to ≥150 million years after the formation of the solar system. Parent-body size played a role in producing variations in absolute HSE abundances among these bodies; however, the oxidation state of the body exerted the major control by influencing the extent to which late-accreted material was mixed into the silicate mantle rather than removed to the core.

Siderophile Elemente: Au, C, Co, Fe, Ge, Ir, Mo, Ni, Os, P, Pd, Pt, Re, Rh, Ru, Sn

 

Martin

[karmaka]

Neues zu Diogeniten und siderophilen Elementen

http://phys.org/news/2012-07-clues-early-solar-ancient-meteorites.html

Examination of the samples determined that the highly siderophile elements present in the diogenite meteorites were present during formation of the rocks, which could only occur if late addition or 'accretion' of these elements after core formation had taken place. This timing of late accretion is earlier than previously thought, and much earlier than similar processes are thought to have occurred on Earth, Mars, or the Moon.

Remarkably, these results demonstrate that accretion, core formation, primary differentiation, and late accretion were all accomplished in just over 2 to 3 million years on some parent bodies. In the case of Earth, there followed crust formation, the development of an atmosphere, and plate tectonics, among other geologic processes, so the evidence for this early period is no longer preserved.

Passend hierzu auch dies:

http://phys.org/news/2012-04-team-asteroids-bombarded-iron-elements.html#nRlv

http://www.sciencemag.org/content/336/6077/72

 

Martin

PS: Vielleicht sollten wir diesen Beitrag besser diesem bereits existierenden thread zuordnen, den ich übersehen hatte  :

http://www.jgr-apolda.eu/index.php?topic=7662.0

Lieber admin, wärest du so nett?

[MetGold]

 
bittesehr! Habe mal die unterschiedlichen Beitragüberschriften vorerst unverändert gelassen!   


   MetGold