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Spectral Distinctions between the Leading and Trailing Hemispheres of Callisto: New Observations

January 1, 1993

An analysis of recent telescopic observations of Callisto results in new insights regarding spectral variations from the leading to the trailing hemisphere of Callisto. Examination of data in the wavelength range from 2.0 to 2.5 ??m indicates that previous suggestions of spectral differences are most likely the result of experimental uncertainty or error. Slight variations in the slope of this wavelength range are consistent with larger ice grain sizes on the trailing hemisphere. The new observations confirm the presence of an absorption feature centered on 3.4 ??m in the spectrum of the leading hemisphere. Theoretical spectral modeling indicates this feature is caused by small amounts of fine-grained water ice. Finally, an absorption feature near 3.1 ??m is indicated but cannot be confirmed due to the strong variation in the spectrum of water ice in this region. If this feature is real, rather than an artifact of the reflectance modeling, it is similar in location and bandwidth to a feature seen in the spectrum of Ceres, attributed to NH4-bearing clays. ?? 1993 Academic Press. All rights reserved.

Publication Year 1993
Title Spectral Distinctions between the Leading and Trailing Hemispheres of Callisto: New Observations
DOI 10.1006/icar.1993.1083
Authors W. M. Calvin, R. N. Clark
Publication Type Article
Publication Subtype Journal Article
Series Title Icarus
Index ID 70017348
Record Source USGS Publications Warehouse