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Galileo SSI lunar observations: Copernican craters and soilsThe Galileo spacecraft completed its first Earth-Moon flyby (EMI) in December 1990 and its second flyby (EM2) in December 1992. Copernican-age craters are among the most prominent features seen in the SSI (Solid-State Imaging) multispectral images of the Moon. The interiors, rays, and continuous ejecta deposits of these youngest craters stand out as the brightest features in images of albedo and visible/1-micron color ratios (except where impact melts are abundant). Crater colors and albedos (away from impact melts) are correlated with their geologic emplacement ages as determined from counts of superposed craters; these age-color relations can be used to estimate the emplacement age (time since impact event) for many Copernican-age craters on the near and far sides of the Moon. The spectral reflectivities of lunar soils are controlled primarily by (1) soil maturity, resulting from the soil's cumulative age of exposure to the space environment; (2) steady-state horizontal and vertical mixing of fresh crystalline materials ; and (3) the mineralogy of the underlying bedrock or megaregolith. Improved understanding of items (1) and (2) above will improve our ability to interpret item (3), especially for the use of crater compositions as probes of crustal stratigraphy. We have examined the multispectral and superposed crater frequencies of large isolated craters, mostly of Eratosthenian and Copernican ages, to avoid complications due to (1) secondaries (as they affect superposed crater counts) and (2) spatially and temporally nonuniform regolith mixing from younger, large, and nearby impacts. Crater counts are available for 11 mare craters and 9 highlands craters within the region of the Moon imaged during EM1. The EM2 coverage provides multispectral data for 10 additional craters with superposed crater counts. Also, the EM2 data provide improved spatial resolution and signal-to-noise ratios over the western nearside.
Document ID
19940011922
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Mcewen, A. S.
(Geological Survey Flagstaff, AZ, United States)
Greeley, R.
(Arizona State Univ. Tempe., United States)
Head, James W.
(Brown Univ. Providence, RI., United States)
Pieters, C. M.
(Brown Univ. Providence, RI., United States)
Fischer, E. M.
(Brown Univ. Providence, RI., United States)
Johnson, T. V.
(Jet Propulsion Lab. California Inst. of Tech., Pasadena., United States)
Neukum, G.
(Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt Berlin, Germany)
Date Acquired
September 6, 2013
Publication Date
January 1, 1993
Publication Information
Publication: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 2: G-M
Subject Category
Lunar And Planetary Exploration
Accession Number
94N16395
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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