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Geology

Article: pp. 343–346 | Full Text | PDF (307K)

Earth-based radar data reveal extended deposits of the Moon's Orientale basin

Rebecca R. Ghent1, Bruce A. Campbell2, B. Ray Hawke3, and Donald B. Campbell4

1 Department of Geology, University of Toronto, 22 Russell Street, Toronto, Ontario M5S 3B1, Canada
2 Center for Earth and Planetary Studies, Smithsonian Institution, MRC 315, Washington, D.C. 20013, USA
3 Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, Honolulu, Hawaii 96822, USA
4 Department of Astronomy, Cornell University, Ithaca, New York 14853, USA

We present new Earth-based radar observations of ejecta associated with the lunar Orientale impact basin. We can distinguish (1) a block-poor ejecta facies composing a concentric halo of mantling material 10 m or greater in thickness that extends more than 1000 km from the basin center, and (2) a melt-rich deposit that forms a discontinuous but areally extensive stratigraphic marker across the southern highlands. The melt-rich component likely extends well into the South Pole–Aitken basin, a key target for future landed and sample return missions. The observation of these two ejecta facies and their distribution across the southern nearside yields new insight into the types and distribution of material contributed by large basin-forming impacts to the highlands megaregolith.

Keywords: Moon, impacts, regolith, radar, Orientale

Received: August 14, 2007; Revised: January 1, 2008; Accepted: January 8, 2008

DOI: 10.1130/G24325A.1

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