SGES Seminars

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Shock metamorphism of Martian meteorites

 

Dr. Ansgar Greshake,
Museum of natural History, Berlin

Date: Wednesday, February 10 at 3:30p.m.
Place: General Sciences Building, Rm. 330

Abstract:

Martian meteorites represent the only solid samples of our neighbouring planet which are available to us for laboratory studies. Up to now 59 unpaired Martian meteorites totalling about 90 kg are recognized. All of them are igneous rocks which formed either by volcanic eruptions or in magma champers in greater depths. Martian meteorites were ejected from Mars in the last 20 million years in 4-8 impact events and document an interplanetary exchange of solid matter, which raises questions regarding the mechanism and the physical conditions during the ejection events. The energy to accelerate Martian surface rocks above escape velocity is governed by shock waves. The process of shock compression and decompression causes significant shock effects in the shocked material, ranging from brittle and ductile deformation to melting or even vaporization. Additionally, shock metamorphism could also lead to the transformation of minerals into their high-pressure polymorphs. Recent progress in characterizing shock effects in Martian meteorites including the discovery of rare high-pressure phases postulated to occur in the Earth’s transition zone as well as a model for the ejection of the meteorites from Mars will be presented.

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