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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, Jörn and Maturilli, Alessandro (2010) Mid-infrared spectral variability for compositionally similar asteroids: Implications for asteroid particle size distributions. Icarus: International Journal of Solar System Studies, 207 (2). Elsevier. doi: 10.1016/j.icarus.2010.01.011.

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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 “compositionally similar” 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, 577-596), 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 μm) 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.

Item URL in elib:https://elib.dlr.de/71457/
Document Type:Article
Title:Mid-infrared spectral variability for compositionally similar asteroids: Implications for asteroid particle size distributions
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Carry, BObservatoire de ParisUNSPECIFIED
Emery, J.Department of Earth and Planetary Sciences, Knoxville, TN 37996-1410, USAUNSPECIFIED
Hora, J.L.Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USAUNSPECIFIED
Cruikshank, D.NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035, USAUNSPECIFIED
Binzel, R.P.Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, MA 02139, USAUNSPECIFIED
Jackson, J.Institute for Astrophysical Research, Boston University, Boston, MA 02215, USAUNSPECIFIED
Helbert, Jörnjoern.helbert (at) dlr.deUNSPECIFIED
Maturilli, Alessandroalessandro.maturilli (at) dlr.deUNSPECIFIED
Date:June 2010
Journal or Publication Title:Icarus: International Journal of Solar System Studies
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1016/j.icarus.2010.01.011
Keywords:Asteroiden, Spektroskopie
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Exploration of the Solar System
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Terahertz and Infrared Sensors
Deposited By: Helbert, Dr.rer.nat. Jörn
Deposited On:08 Nov 2011 10:28
Last Modified:20 Mar 2013 19:44

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