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Analysis of crater distribution in mare units on the lunar far sideMare material is asymmetrically distributed on the moon. The earth-facing hemisphere, where the crust is believed to be 26 km thinner than on the farside, contains substantially more basaltic mare material. Using Lunar Topographic Orthophoto Maps, the thickness of the mare material in three farside craters, Aitken (0.59 km), Isaev (1.0 km), and Tsiolkovskiy (1.75 km) was calculated. Crater frequency distribution in five farside mare units (Aitken, Isaev, Lacus Solitudinis, Langemak, and Tsiolkovskiy) and one light plains unit (in Mendeleev) were also studied. Nearly 10,000 farside craters were counted. Analysis of the crater frequency on the light plains unit gives an age of 4.3 billion yr. Crater frequency distributions on the mare units indicate ages of 3.7 and 3.8 billion yr. suggesting that the units are distributed over a narrow time period of approximately 100 million yr. Returned lunar samples from nearside maria give dates as young as 3.1 billion yr. The results of this study suggest that mare basalt emplacement on the far side ceased before it did on the near side.
Document ID
19830033651
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Walker, A. S.
(National Air and Space Museum Washington, DC, United States)
El-Baz, F.
(National Air and Space Museum Washington, DC, United States)
Date Acquired
August 11, 2013
Publication Date
August 1, 1982
Publication Information
Publication: Moon and the Planets
Volume: 27
Subject Category
Lunar And Planetary Exploration
Accession Number
83A14869
Funding Number(s)
CONTRACT_GRANT: NSG-7188
Distribution Limits
Public
Copyright
Other

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