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Geology of the Gusec cratered plains from the Spirit rover transverseThe cratered plains of Gusev traversed by Spirit are generally low-relief rocky plains dominated by impact and eolian processes. Ubiquitous shallow, soil-filled, circular depressions, called hollows, are modified impact craters. Rocks are dark, fine-grained basalts, and the upper 10 m of the cratered plains appears to be an impact-generated regolith developed over intact basalt flows. Systematic field observations across the cratered plains identified vesicular clasts and rare scoria similar to original lava flow tops, consistent with an upper inflated surface of lava flows with adjacent collapse depressions. Crater and hollow morphometry are consistent with most being secondaries. The size frequency distribution of rocks >0.1 m diameter generally follows exponential functions similar to other landing sites for total rock abundances of 5-35%. Systematic clast counts show that areas with higher rock abundance and more large rocks have higher thermal inertia. Plains with lower thermal inertia have fewer rocks and substantially more pebbles that are well sorted and evenly spaced, similar to a desert pavement or lag. Eolian bed forms (ripples and wind tails) have coarse surface lags, and many are dust covered and thus likely inactive. Deflation of the surface _5-25 cm likely exposed two-toned rocks and elevated ventifacts and transported fines into craters creating the hollows. This observed redistribution yields extremely slow average erosion rates of _0.03 nm/yr and argues for very little long-term net change of the surface and a dry and desiccating environment similar to today's since the Hesperian (or _3 Ga).
Document ID
20060044033
Acquisition Source
Jet Propulsion Laboratory
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Golombek, M. P.
Crumpler, L. S.
Grant, J. A.
Greely, R.
Cabrol, N. A.
Parker, T. J.
Rice, J. W., Jr.
Ward, J. G.
Arvidson, R. E.
Moersch, J. E.
Fergason, J. F.
Christensen, P. R.
Castano, A.
Castano, R.
Haldemann, A. F. C.
Li, R.
Bell, J. F., III
Squyres, S. W.
Date Acquired
August 23, 2013
Publication Date
January 12, 2006
Publication Information
Publication: Journal of Geophysical Research
Volume: 111
Subject Category
Geophysics
Distribution Limits
Public
Copyright
Other
Keywords
Spirit
Gusev
Mars Exploration Rover (MER)

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