Preimpact porosity controls the gravity signature of lunar craters. Issue 22 (19th November 2015)

• Record Type: Journal Article
• Authors: 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.
• Is Part Of: Geophysical research letters. Volume 42:Issue 22(2015:Nov.)
• Page Start: 9711
• Page End: 9716
• Publication Date: 2015-11-19
• Subjects: Lunar -- impact crater -- porosity -- Gravity Recovery and Interior Laboratory -- GRAIL -- gravity; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2015GL066198
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 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. Key Points: The positive gravity signature of craters is due to initial porosity compaction Porosity is responsible for the observed scatter in the Bouguer anomalies Mantle uplift dominates the gravity for craters larger than ~215 km in diameter