Tomas Kohout^a,b,*, Maria Gritsevich^c,d,e, Victor I. Grokhovsky^f, Grigoriy A. Yakovlev^f, Jakub Haloda^g,h, Patricie Halodova^g, Radoslaw M. Michallikⁱ, Antti Penttilä^a, Karri Muinonen^a,c

^aDepartment of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki University, Finland
^bInstitute of Geology, Academy of Sciences of the Czech Republic, Rozvojová 269, 16500 Prague 6, Czech Republic
^cFinnish Geodetic Institute, Geodeetinrinne 2, P.O. Box 15, FI-02431 Masala, Finland
^dInstitute of Mechanics, Lomonosov Moscow State University, Michurinsky prt., 1, 119192, Moscow, Russia
^eRussian Academy of Sciences, Dorodnicyn Computing Centre, Department of Computational Physics, Vavilova ul. 40, 119333 Moscow, Russia
^fUral Federal University, Ekaterinburg, Russia
^gCzech Geological Survey, Geologická 6, 152 00 Praha 5, Czech Republic
^hOxford Instruments NanoAnalysis, Halifax Road, High Wycombe, Bucks, HP12 3SE, United Kingdom
ⁱDepartment of Geosciences and Geography, University of Helsinki, P.O. Box 64, 00014 Helsinki University, Finland

The mineralogy and physical properties of Chelyabinsk meteorites (fall, February 15, 2013) are presented. Three types of meteorite material are present, described as the light-colored, dark-colored, and impact-melt lithologies. All are of LL5 composition with the impact-melt lithology being close to whole-rock melt and the dark-colored lithology being shock-darkened due to partial melting of iron metal and sulfides. This enables us to study the effect of increasing shock on material with identical composition and origin. Based on the magnetic susceptibility, the Chelyabinsk meteorites are richer in metallic iron as compared to other LL chondrites. The measured bulk and grain densities and the porosity closely resemble other LL chondrites. Shock-darkening does not have a significant effect on the material physical properties, but causes a decrease of reflectance and decrease in silicate absorption bands in the reflectance spectra. This is similar to the space weathering effects observed on asteroids. However, compared to space weathered materials, there is a negligible to minor slope change observed in impact-melt and shock-darkened meteorite spectra. Thus, it is possible that some dark asteroids with invisible silicate absorption bands may be composed of relatively fresh shock-darkened chondritic material.

Reference
Kohout T, Gritsevich M, Grokhovsky VI, Yakovlev GA, Haloda J, Halodova P, Michallik RM, Penttilä A and Muinonen K (in press) Mineralogy, reflectance spectra, and physical properties of the Chelyabinsk LL5 chondrite – insight into shock-induced changes in asteroid regoliths. Icarus
[doi:10.1016/j.icarus.2013.09.027]
Copyright Elsevier

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