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Near-Infrared Spectrophotometry of Phobos and DeimosWe have observed the leading and trailing hemispheres of Phobos from 1.65 to 3.5 microns and Deimos from 1.65 to 3.12 microns near opposition. We find the trailing hemisphere of Phobos to be brighter than its leading hemisphere by 0.24 +/- 0.06 magnitude at 1.65 microns and brighter than Deimos by 0.98 +/- 0.07 magnitude at 1.65 microns. We see no difference larger than observational uncertainties in spectral slope between the leading and trailing hemispheres when the spectra are normalized to 1.65 microns. We find no 3-microns absorption feature due to hydrated minerals on either hemisphere to a level of approx. 5 - 10% on Phobos and approx. 20% on Deimos. When the infrared data are joined to visible and near-IR data obtained by previous workers, our data suggest the leading (Stickney-dominated) side of Phobos is best matched by T-class asteroids. The spectral slope of the trailing side of Phobos and leading side of Deimos are bracketed by the D-class asteroids. The best laboratory spectral matches to these parts of Phobos are mature lunar soils and heated carbonaceous chondrites. The lack of 3-microns absorption features on either side of Phobos argues against the presence of a large interior reservoir of water ice according to current models of Phobos' interior.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Rivkin, A. S. (Arizona Univ. Tucson, AZ, United States)
Brown, R. H. (Arizona Univ. Tucson, AZ, United States)
Trilling, D. E. (Pennsylvania Univ. Philadelphia, PA, United States)
Bell, J. F., III (Cornell Univ. Ithaca, NY, United States)
Plassmann, J. H. (Arizona Univ. Tucson, AZ, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2002
Publication Information
Publication: Icarus
Volume: 156
ISSN: 0019-1035
Subject Category
Lunar and Planetary Science and Exploration
Funding Number(s)
Distribution Limits