Meteorite-Mineralien-Gold-Forum.de
Meteoriten => Meteorite => Thema gestartet von: karmaka am November 15, 2012, 22:54:29 Nachmittag
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Neues zum Ursprung der Pallasite
http://www.rochester.edu/news/show.php?id=4972
John Tarduno at the University of Rochester, has shown that the pallasites were likely formed when a smaller asteroid crashed into a planet-like body about 30 times smaller than earth, resulting in a mix of materials that make up the distinctive meteorites.
"The findings by John Tarduno and his team turn the original pallasite formation model on its head," said Joshua Feinberg, assistant professor of earth sciences at the University of Minnesota [...] Pallasites are made of iron-nickel and the translucent, gem-like mineral olivine, leading many scientists to assume they were formed where those two materials typically come together—at the boundary of the iron core and rocky mantle in an asteroid or other planetary body. Tarduno discovered that tiny metal grains in the olivine were magnetized in a common direction, a revelation that led the researchers to conclude that the pallasites must have been formed much farther from the core.
"We think the iron-nickel in the pallasites came from a collision with an asteroid," said research team member Francis Nimmo, professor of earth and planetary sciences at the University of California Santa Cruz. "Molten iron from the core of the smaller asteroid was injected into the mantle of the larger body, creating the textures we see in the pallasites."
"Previous thinking had been that iron was squeezed up from the core into olivine in the mantle," said Tarduno. "The magnetic grains in the olivine showed that was not the case." [...] The measurements helped the scientists to classify the parent body of the pallasites. Tarduno said a 200 km radius made the body large enough to be considered a protoplanet—a small celestial object with the potential of developing into planets.
Their work also helped clear up questions about whether small celestial bodies were capable of having dynamo activity—a rotating, liquid iron core that can create a magnetic field. "Our magnetic data join mounting evidence from meteorites that small bodies can, indeed, have dynamo action," said Tarduno.
Interessant!
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Sky & Telescope, June 2015, pp. 12+13: Meteorites - Long-lived magnetic fields left their marks (News Notes)
Bernd :winke: