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Mid-infrared spectral variability for compositionally similar asteroids: Implications for asteroid particle size distributions

Vernazza, P. and Carry, B. and Emery, J. and Hora, J.L. and Cruikshank, D. and Binzel, R.P. and Jackson, J. and Helbert, J. and Maturilli, A. (2010) Mid-infrared spectral variability for compositionally similar asteroids: Implications for asteroid particle size distributions. Icarus: International Journal of Solar System Studies, 207 (2), pp. 800-809. Elsevier. DOI: 10.1016/j.icarus.2010.01.011.

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Official URL: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-4Y6S7PT-3&_user=100058&_coverDate=06%2F30%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000007338&_version=1&_urlVersion=0&_userid=100058&md5=6dbf6d7fa

Abstract

We report an unexpected variability among mid-infrared spectra (IRTF and Spitzer data) of eight S-type asteroids for which all other remote sensing interpretations (e.g. VNIR spectroscopy, albedo) yield similar compositions. Compositional fitting making use of their mid-IR spectra only yields surprising alternative conclusions: (1) these objects are not â��compositionally similarâ�� as the inferred abundances of their main surface minerals (olivine and pyroxene) differ from one another by 35% and (2) carbonaceous chondrite and ordinary chondrite meteorites provide an equally good match to each asteroid spectrum. Following the laboratory work of Ramsey and Christensen (Ramsey, M.S., Christensen, P.R. [1998]. J. Geophys. Res. 103, 577â��596), we interpret this variability to be physically caused by differences in surface particle size and/or the effect of space weathering processes. Our results suggest that the observed asteroids must be covered with very fine (<5 �¼m) dust that masks some major and most minor spectral features. We speculate that the compositional analysis may be improved with a spectral library containing a wide variety of well characterized spectra (e.g., olivine, orthopyroxene, feldspar, iron, etc.) obtained from very fine powders. In addition to the grain size effect, space weathering processes may contribute as well to the reduction of the spectral contrast. This can be directly tested via new laboratory irradiation experiments.

Document Type:Article
Title:Mid-infrared spectral variability for compositionally similar asteroids: Implications for asteroid particle size distributions
Authors:
AuthorsInstitution or Email of Authors
Vernazza, P.Research and Scientific Support Department, European Space Agency, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
Carry, B.Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique, Observatoire de Paris, 5 Place Jules Janssen, Meudon F-92195, France
Emery, J.Department of Earth and Planetary Sciences, Knoxville, TN 37996-1410, USA
Hora, J.L.Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
Cruikshank, D.NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035, USA
Binzel, R.P.NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035, USA
Jackson, J.Institute for Astrophysical Research, Boston University, Boston, MA 02215, USA
Helbert, J.Joern.Helbert@dlr.de
Maturilli, A.Alessandro.Maturilli@dlr.de
Date:June 2010
Journal or Publication Title:Icarus: International Journal of Solar System Studies
Refereed publication:Yes
In Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:207
DOI:10.1016/j.icarus.2010.01.011
Page Range:pp. 800-809
Publisher:Elsevier
Status:Published
Keywords:Asteroids; Surfaces; Spectroscopy; Mineralogy; Meteorites
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EW - Erforschung des Weltraums
DLR - Research area:Space
DLR - Program:W EW - Erforschung des Weltraums
DLR - Research theme (Project):W - Vorhaben Asteroiden und Kometen (old)
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Terahertz and Infrared Sensors
Deposited By: Alessandro Maturilli
Deposited On:11 Jan 2011 15:03
Last Modified:12 Dec 2013 21:12

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