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Multiple Asteroid Systems: Dimensions and Thermal Properties from Spitzer Space Telescope and Ground-based ObservationsWe collected mid-IR spectra from 5.2 to 38 microns using the Spitzer Space Telescope Infrared Spectrograph of 28 asteroids representative of all established types of binary groups. Photometric light curves were also obtained for 14 of them during the Spitzer observations to provide the context of the observations and reliable estimates of their absolute magnitudes. The extracted mid-IR spectra were analyzed using a modified standard thermal model (STM) and a thermophysical model (TPM) that takes into account the shape and geometry of the large primary at the time of the Spitzer observation. We derived a reliable estimate of the size, albedo, and beaming factor for each of these asteroids, representing three main taxonomic groups: C, S, and X. For large (volume-equivalent system diameter Deq > 130 km) binary asteroids, the TPM analysis indicates a low thermal inertia (Lambda < or = approx.100 J/1/2 s/K/sq m2) and their emissivity spectra display strong mineral features, implying that they are covered with a thick layer of thermally insulating regolith. The smaller (surface-equivalent system diameter Deff < 17 km) asteroids also show some emission lines of minerals, but they are significantly weaker, consistent with regoliths with coarser grains, than those of the large binary asteroids. The average bulk densities of these multiple asteroids vary from 0.7-1.7 g/cu cm (P-, C-type) to approx. 2 g/cu cm (S-type). The highest density is estimated for the M-type (22) Kalliope (3.2 +/- 0.9 g/cu cm). The spectral energy distributions (SEDs) and emissivity spectra, made available as a supplement document, could help to constrain the surface compositions of these asteroids.
Document ID
20130014861
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1016/j.icarus.2012.09.013
Authors
Marchis, F. (Search for Extraterrestrial Intelligence Inst. Mountain View, CA, United States)
Enriquez, J. E. (Search for Extraterrestrial Intelligence Inst. Mountain View, CA, United States)
Emery, J. P. (Tennessee Univ. Knoxville, TN, United States)
Mueller, M. (Space Research Organization Netherlands Groningen, Netherlands)
Baek, M. (Search for Extraterrestrial Intelligence Inst. Mountain View, CA, United States)
Pollock, J. (Appalachian State Univ. Boone, NC, United States)
Assafin, M. (Observatorio do Valongo Rio de Janeiro)
Matins, R. Vieira (National Observatory Rio de Janeiro, Brazil)
Berthier, J. (Observatoire de Paris France)
Vachier, F. (Observatoire de Paris France)
Cruikshank, D. P. (NASA Ames Research Center Moffett Field, CA, United States)
Lim, L. F. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Reichart, D. E. (North Carolina Univ. Chapel Hill, NC, United States)
Ivarsen, K. M. (North Carolina Univ. Chapel Hill, NC, United States)
Haislip, J. B. (North Carolina Univ. Chapel Hill, NC, United States)
LaCluyze, A. P. (North Carolina Univ. Chapel Hill, NC, United States)
Date Acquired
December 26, 2013
Publication Date
October 2, 2012
Publication Information
Publication: Icarus
Volume: 221
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
GSFC-E-DAA-TN8899
Distribution Limits
Public
Copyright
Public Use Permitted.

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