Universität zu Köln

Weber, I., Morlok, A., Bischoff, A., Hiesinger, H., Ward, D., Joy, K. H., Crowther, S. A., Jastrzebski, N. D., Gilmour, J. D., Clay, P. L., Wogelius, R. A., Greenwood, R. C., Franchi, I. A. and Muenker, C. (2016). Cosmochemical and spectroscopic properties of Northwest Africa 7325-A consortium study. Meteorit. Planet. Sci., 51 (1). S. 3 - 31. HOBOKEN: WILEY. ISSN 1945-5100

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Abstract

This work is part of a project to build an infrared database in order to link IR data of planetary materials (and therefore possible Mercury material) with remote sensing observations of Mercury, which will probably be obtained by the MERTIS instrument on the forthcoming BepiColombo mission. The unique achondrite Northwest Africa (NWA) 7325, which has previously been suggested to represent the first sample from Mercury, was investigated by optical and electron microscopy, and infrared and Raman spectroscopy. In addition, the oxygen, strontium, xenon, and argon isotopes were measured and the abundance of selected trace elements determined. The meteorite is a cumulate rock with subchondritic abundances of HFSE and REE and elevated Sr contents, which underwent a second heating and partial remelting process. Oxygen isotope measurements show that NWA 7325 plots in the ureilite field, close to the ALM-A trachyandesitic fragment found in the unique Almahata Sitta meteorite breccia. On the other hand, mineralogical investigations of the pyroxenes in NWA 7325 provide evidence for similarities to the lodranites and acapulcoites. Furthermore, the rock is weakly shocked and argon isotope data record ancient (similar to 4.5 Ga) plateau ages that have not been reset. The sample records a cosmogenic exposure age of similar to 19 Ma. Systematics of Rb-Sr indicate an extreme early volatile depletion of the precursor material, similar to many other achondrite groups. However, despite its compositional similarities to other meteorite groups, our results suggest that this meteorite is unique and unrelated to any other known achondrite group. An origin for NWA 7325 as a sample from the planet Mercury is not supported by the results of our investigation. In particular, the evidence from infrared spectroscopy indicates that a direct relationship between NWA 7325 and the planet Mercury can be ruled out: no acceptable spectral match between laboratory analyses and remote sensing observations from Mercury has been obtained. However, we demonstrate that infrared spectroscopy is a rapid and nondestructive method to characterize mineral phases and thus an excellent tool for planetary surface characterization in space missions.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Weber, I. UNSPECIFIED UNSPECIFIED UNSPECIFIED Morlok, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bischoff, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hiesinger, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ward, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Joy, K. H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Crowther, S. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Jastrzebski, N. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gilmour, J. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Clay, P. L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wogelius, R. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Greenwood, R. C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Franchi, I. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Muenker, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-293031
DOI:	10.1111/maps.12586
Journal or Publication Title:	Meteorit. Planet. Sci.
Volume:	51
Number:	1
Page Range:	S. 3 - 31
Date:	2016
Publisher:	WILEY
Place of Publication:	HOBOKEN
ISSN:	1945-5100
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language RAMAN-SPECTROSCOPY; OXYGEN-ISOTOPE; LATTICE-DYNAMICS; MERCURYS SURFACE; SPECTRA; TERRESTRIAL; CHONDRITES; OLIVINE; CONSTRAINTS; METEORITES Multiple languages Geochemistry & Geophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/29303