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The Age of Lunar South Circumpolar Craters Haworth, Shoemaker, Faustini, and Shackleton: Implications for Regional Geology, Surface Processes, and Volatile SequestrationThe interiors of the lunar south circumpolar craters Haworth, Shoemaker, Faustini, and Shackleton contain permanently shadowed regions (PSRs) and have been interpreted to contain sequestered volatiles including water ice. Altimetry data from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter provide a new means of examining the permanently shadowed interiors of these craters in unprecedented detail. In this study, we used extremely high-resolution gridded LOLA data of Haworth, Shoemaker, Faustini, and Shackleton to determine the size-frequency distributions and the spatial density of craters superposing their rims, inner slopes, and floors. Based on their population of superposed D greater than or equal to 2 km craters, Haworth, Shoemaker, and Faustini have pre-Nectarian formation ages. Shackleton is interpreted as having a Late Imbrian age on the basis of craters with diameter D greater than or equal to 0.5 km superposed on its rim. The local density of craters with sub-km diameters across our study area is strongly dependent on slope; because of its steep interior slopes, the lifetime of craters on the interior of Shackleton is limited. The slope-dependence of the small crater population implies that the population in this size range is controlled primarily by the rate at which craters are destroyed. This is consistent with the hypothesis that crater removal and resurfacing is a result of slopedependent processes such as diffusive mass wasting and seismic shaking, linked to micrometeorite and meteorite bombardment. Epithermal neutron flux data and UV albedo data show that these circumpolar PSRs, particularly Shoemaker, may have approximately 1-2% water ice by mass in their highly porous surface regolith, and that Shoemaker may have approximately 5% or more water ice by mass in the near subsurface. The ancient formation ages of Shoemaker, Faustini and Haworth, and the Late Imbrian (approximately 3.5 Ga) crater retention ages of their floors suggests that any water ice that might have been deposited in their permanently shadowed areas was insufficient to modify the superposed crater population since that time.
Document ID
20150006822
Acquisition Source
Goddard Space Flight Center
Document Type
Accepted Manuscript (Version with final changes)
External Source(s)
Authors
A R Tye (Brown University Providence, Rhode Island, United States)
C I Fassett (Mount Holyoke College South Hadley, Massachusetts, United States)
J W Head (Brown University Providence, Rhode Island, United States)
E Mazarico (Goddard Space Flight Center Greenbelt, Maryland, United States)
A T Basilevsky (Academy of Sciences (Russia) Moscow, Russian Federation)
G A Neumann (Goddard Space Flight Center Greenbelt, Maryland, United States)
D E Smith (Massachusetts Institute of Technology Cambridge, Massachusetts, United States)
M T Zuber (Massachusetts Institute of Technology Cambridge, Massachusetts, United States)
Date Acquired
April 27, 2015
Publication Date
March 25, 2015
Publication Information
Publication: Icarus
Publisher: Elsevier
Volume: 255
Issue Publication Date: July 15, 2015
e-ISSN: 1090-2643
DOI: doi:10.1016/j.icarus.2015.03.016
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
GSFC-E-DAA-TN22069
E-ISSN: 1090-2643
Report Number: GSFC-E-DAA-TN22069
Funding Number(s)
CONTRACT_GRANT: NNX13AJ86G
CONTRACT_GRANT: NNA14AB01A
CONTRACT_GRANT: NNX13AO77G
CONTRACT_GRANT: NNX11AK29G
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Circumpolar
LOLA
LUNAR

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