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Preimpact porosity controls the gravity signature of lunar craters
Author(s) -
Milbury C.,
Johnson B. C.,
Melosh H. J.,
Collins G. S.,
Blair D. M.,
Soderblom J. M.,
Nimmo F.,
Bierson C. J.,
Phillips R. J.,
Zuber M. T.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl066198
Subject(s) - impact crater , geology , porosity , bouguer anomaly , crust , mantle (geology) , lunar craters , mineralogy , geophysics , petrology , gravity anomaly , astrobiology , geotechnical engineering , paleontology , physics , oil field
We model the formation of lunar complex craters and investigate the effect of preimpact porosity on their gravity signatures. We find that while preimpact target porosities less than ~7% produce negative residual Bouguer anomalies (BAs), porosities greater than ~7% produce positive anomalies whose magnitude is greater for impacted surfaces with higher initial porosity. Negative anomalies result from pore space creation due to fracturing and dilatant bulking, and positive anomalies result from destruction of pore space due to shock wave compression. The central BA of craters larger than ~215 km in diameter, however, are invariably positive because of an underlying central mantle uplift. We conclude that the striking differences between the gravity signatures of craters on the Earth and Moon are the result of the higher average porosity and variable porosity of the lunar crust.