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Mid-infrared spectra of binary asteroids with Spitzer/IRS

Marchis, F. and Emery, J.P. and Iglesias, J. and Pollock, J. and Mueller, M and Harris, A.W. and Michalowski, T. and Berthier, J. and Descamps, P. (2008) Mid-infrared spectra of binary asteroids with Spitzer/IRS. In: American Astronomical Society, Division of Planetary Sciences Meeting 2008, 40 (60.04). American Astronomical Society. American Astronomical Society, Division of Planetary Sciences Meeting 2008, 2008-10-10 - 2008-10-15, Ithaca, NY (USA).

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Abstract

To date, 162 asteroids are known to be binary or multiple systems. Insights, such as the size and shape of their components, the nature of their surface, their bulk density are the key to understanding how these multiple asteroidal systems formed. We obtained 19.9h of observations using the Spitzer/IRS instrument to observe 26 known binary systems: 17 main-belt asteroids and 9 near-Earth asteroids. The low-resolution (R=100-600) thermal spectra (5-42 um) recorded by this instrument provide a powerful means of determining the asteroid size and albedo, as well as other physical properties, such as shape, spin state, thermal inertia, and surface roughness. Additionally, thermal emissivity spectra have strong silicate features (Si-O stretch and bend fundamentals at 10 and 20 um), which can be used to characterize the surfaces of asteroids and infer the best meteorite analog. To be able to recover the geometry of the binary system at the time of Spitzer observations, we initiated a large campaign of photometric observations with a worldwide network of observatories to measure lightcurves. We also recorded high S/N reflectance spectra in the visible and near-infrared using the IRTF and Lick telescopes. This survey is currently being conducted and the thermal infrared spectra of 23 binary asteroids have been successfully recorded. We will present their analysis emphasizing how these bulk density measurements are related to their taxonomic classes. Preliminary results suggest that C-type binary asteroids are composed of lower density material (bulk density of 1.2 g/cm3), than S-type asteroids ( 2.2 g/cm3), and the M-type Kalliope ( 3.3 g/cm3, see Descamps et al., Icarus, 2008). Their bulk density is systematically lower than their meteorite analogs suggesting a significant porosity of 30-50%. This research was supported by NASA PAST NNX07AP70G and it is based on Spitzer space telescope, which is operated by JPL under a contract with NASA.

Document Type:Conference or Workshop Item (Paper)
Title:Mid-infrared spectra of binary asteroids with Spitzer/IRS
Authors:
AuthorsInstitution or Email of Authors
Marchis, F.SETI Institute/University of California, Berkeley, USA
Emery, J.P.SETI Institute
Iglesias, J.SETI Institute/University of California, Berkeley, USA
Pollock, J.Dept of Physics and Astronomy, Appalachian State University, USA
Mueller, MSteward Observatory, University of Arizona, USA
Harris, A.W.UNSPECIFIED
Michalowski, T.Astronomical Observatory, Adam Mickiewicz University, Poland
Berthier, J.IMCCE, Observatoire de Paris, France
Descamps, P.IMCCE, Observatoire de Paris, France
Date:September 2008
Journal or Publication Title:American Astronomical Society, Division of Planetary Sciences Meeting 2008
Refereed publication:No
In SCOPUS:No
In ISI Web of Science:No
Volume:40
Editors:
EditorsEmail
American Astronomical Society, UNSPECIFIED
Publisher:American Astronomical Society
Status:Published
Keywords:Asteroids,Infrared,Spectroscopy
Event Title:American Astronomical Society, Division of Planetary Sciences Meeting 2008
Event Location:Ithaca, NY (USA)
Event Type:international Conference
Event Dates:2008-10-10 - 2008-10-15
Organizer:American Astronomical Society
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 > Asteroids and Comets
Deposited By: Prof. Alan Harris
Deposited On:25 Nov 2008
Last Modified:27 Apr 2009 15:16

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