date: 2012 April 4 (Wed) 15:00-16:00
room: CPS Conference Room
speaker: Takashi Mikouchi (The University of Tokyo)
organizer: Hiroshi Kimura
title: "Dark" olivine in Martian meteorites: The formation of iron nano-particles by shock metamorphism
abstract: Many Martian meteorites contain black-colored olivine grains. We observed these olivine grains by transmission electron microscope (TEM) and found that nano-particles of either Fe metal or magnetite (10-20 nm in diameter) are present, which is responsible for the black color. We performed shock experiments on olivine and successfully reproduced nano-particles at the shock pressure higher than 40 GPa, which is consistent with the estimated shock pressure of Martian meteorites containing black olivine.
The presence of two different nano-particle species can be explained by the difference of temperature increase during shock. The presence of nano-particles changes the reflectance spectra and magnetic susceptibility of olivine. Thus, it is necessary to consider the effect when we interpret the remote sensing data.
keywords: Martian meteorites, olivine, nano-particles, shock metamorphism, remote sensing