Magnetism and mineralogy of Almahata Sitta polymict ureilite (= asteroid 2008 TC3): Implications for the ureilite parent body magnetic field |
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| Authors: | Viktor H HOFFMANN Rupert HOCHLEITNER Masayuki TORII Minoru FUNAKI Takashi MIKOUCHI Melanie KALIWODA Peter JENNISKENS Muawia H SHADDAD |
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| Institution: | 1. Department of Geo‐ and Environmental Sciences, University of Muenchen, Theresienstrasse 41, 80333 Muenchen, Germany;2. Department of Geosciences, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany;3. Mineralogical State Collection, Theresienstrasse 41, 80333 Muenchen, Germany;4. Department of Geosphere‐Biosphere System Science, Okayama University of Science, 1‐1 Ridaicho, Okayama 700‐005, Japan;5. National Institute of Polar Research, 10‐3 Midori‐cho, Tachikawa/Tokyo 190‐8518, Japan;6. Department of Earth and Planetary Science, University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku, Tokyo 113‐0033, Japan;7. Carl Sagan Center, SETI Institute, 189 Bernardo Ave., Mountain View, California 94043, USA;8. Department of Physics and Astronomy, University of Khartoum, P.O. Box 321, Khartoum 11115, Sudan |
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| Abstract: | Abstract– The Almahata Sitta meteorite is the first case of recovered extraterrestrial material originating from an asteroid that was detected in near Earth space shortly before entering and exploding in the high atmosphere. The aims of our project within the 2008 TC3 consortium were investigating Almahata Sitta’s (AS) magnetic signature, phase composition and mineralogy, focussing on the opaque minerals, and gaining new insights into the magnetism of the ureilite parent body (UPB). We report on the general magnetic properties and behavior of Almahata Sitta and try to place the results in context with the existing data set on ureilites and ureilite parent body models. The magnetic signature of AS is dominated by a set of low‐Ni kamacites with large grain sizes. Additional contributions come from micron‐sized kamacites, suessite, (Cr) troilite, and daubreelite, mainly found in the olivine grains adjacent to carbon‐rich veins. Our results show that the paleomagnetic signal is of extraterrestrial origin as can be seen by comparing with laboratory produced magnetic records (IRM). Four types of kamacite (I–IV) have been recognized in the sample. The elemental composition of the ureilite vein metal Kamacite I (particularly Co) clearly differs from the other kamacites (II‐IV), which are considered to be indigenous. Element ratios of kamacite I indicate that it was introduced into the UPB by an impactor, supporting the conclusions of Gabriel and Pack (2009) . |
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