The fractured Moon: Production and saturation of porosity in the lunar highlands from impact cratering

Jason Soderblom (1) , Alexander Evans , Brandon Johnson , H. Jay Melosh (2) , Katarina Miljković , Roger Phillips (3) , Jeffrey Andrews‐hanna , Carver Bierson , James Head , Colleen Milbury , Gregory Neumann , Francis Nimmo (4) , David Smith , Sean Solomon , Michael Sori , Mark Wieczorek (5) , Maria Zuber

1 University of Arizona
2 EAPS - Department of Earth, Atmospheric, and Planetary Sciences [West Lafayette]
3 Department of Earth and Planetary Sciences [St Louis]
4 Department of Earth and Planetary Sciences [Santa Cruz]
5 IPGP - Institut de Physique du Globe de Paris

We have analyzed the Bouguer anomaly (BA) of~1200 complex craters in the lunar highlands from Gravity Recovery and Interior Laboratory observations. The BA of these craters is generally negative, though positive BA values are observed, particularly for smaller craters. Crater BA values scale inversely with crater diameter, quantifying how larger impacts produce more extensive fracturing and dilatant bulking. The Bouguer anomaly of craters larger than 93 þ 47 À19 km in diameter is independent of crater size, indicating that there is a limiting depth to impact-generated porosity, presumably from pore collapse associated with either overburden pressure or viscous flow. Impact-generated porosity of the bulk lunar crust is likely in a state of equilibrium for craters smaller than~30 km in diameter, consistent with an~8 km thick lunar megaregolith, whereas the gravity signature of larger craters is still preserved and provides new insight into the cratering record of even the oldest lunar surfaces.

Domaines: Planétologie

Jason Soderblom, Alexander Evans, Brandon Johnson, H. Jay Melosh, Katarina Miljković, et al.. The fractured Moon: Production and saturation of porosity in the lunar highlands from impact cratering. Geophysical Research Letters, 2015, 42 (17), pp.6939-6944. ⟨10.1002/2015GL065022⟩. ⟨hal-02458611⟩