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distal ejecta from lunar impacts: extensive regions of rocky depositsLunar Reconnaissance Orbiter (LRO) Diviner Radiometer, Mini-RF, and LRO Camera data were used to identify and characterize rocky lunar deposits that appear well separated from any potential source crater. Two regions are described: 1) A approximate 18,000 sq km area with elevated rock abundance and extensive melt ponds and veneers near the antipode of Tycho crater (167.5 deg E, 42.5 deg N). This region has been identified previously, using radar and aging data. 2) A much larger and more diffuse region, covering approximately 730,000 sq km, centered near 310 deg E, 35 deg S, containing elevated rock abundance and numerous granular flow deposits on crater walls. The rock distributions in both regions favor certain slope azimuths over others, indicating a directional component to the formation of these deposits. The spatial distribution of rocks is consistent with the arrival of ejecta from the west and northwest at low angles (approximately 10-30 deg) above the horizon in both regions. The derived age and slope orientations of the deposits indicate that the deposits likely originated as ejecta from the Tycho impact event. Despite their similar origin, the deposits in the two regions show significant differences in the datasets. The Tycho crater antipode deposit covers a smaller area, but the deposits are pervasive and appear to be dominated by impact melts. By contrast, the nearside deposits cover a much larger area and numerous granular flows were triggered. However, the features in this region are less prominent with no evidence for the presence of impact melts. The two regions appear to be surface expressions of a distant impact event that can modify surfaces across wide regions, resulting in a variety of surface morphologies. The Tycho impact event may only be the most recent manifestation of these processes, which likely have played a role in the development of the regolith throughout lunar history
Document ID
20170003183
Document Type
Reprint (Version printed in journal)
Authors
Bandfield, Joshua L.
(Space Science Inst. Boulder, CO, United States)
Cahill, Joshua T. S.
(Johns Hopkins Univ. Laurel, MD, United States)
Carter, Lynn M.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Neish, Catherine D.
(University of Western Ontario London, Ontario, Canada)
Patterson, G. Wesley
(Johns Hopkins Univ. Laurel, MD, United States)
Williams, Jean-Pierre
(California Univ. Los Angeles, CA, United States)
Paige, David A.
(California Univ. Los Angeles, CA, United States)
Date Acquired
April 7, 2017
Publication Date
May 11, 2016
Publication Information
Publication: Icarus
Volume: 283
ISSN: 0019-1035
Subject Category
Lunar and Planetary Science and Exploration
Report/Patent Number
GSFC-E-DAA-TN40588
Distribution Limits
Public
Copyright
Other