Abstract
AbstractLateral variations in bulk density and porosity of the upper lunar highland crust are mapped using a high‐resolution Gravity Recovery and Interior Laboratory (GRAIL) gravity field model and Lunar Reconnaissance Orbiter (LRO) derived topography. With a higher spatial resolution gravity model than previous studies, we focus on individual impact basins with diameters greater than 200 km. The bulk density of the upper few kilometers of the lunar crust is estimated by minimizing the correlation between the topography and Bouguer gravity at short wavelengths that are unaffected by lithospheric flexure. Porosity is then derived using estimates of the grain density obtained from remote sensing data of the surface composition. The near surface crust in proximity to many large basins is found to exhibit distinct radial porosity signatures. Low porosities are found in the basin centers within the peak ring, whereas high porosities are identified near and just exterior to the main rim. The larger basins exhibit a more pronounced porosity signature than the smaller basins. Though the number of basins investigated in this study is limited, younger basins appear to be associated with the largest amplitude variations in porosity. For basins with increasing age the magnitude of the porosity variations decreases.
Highlights
High resolution data from the Gravity Recovery and Interior Laboratory (GRAIL) mission (Zuber et al, 2013a) allowed to investigate physical characteristics of the lunar interior
Analyses were performed on an equal area grid with a spacing of 0.75◦, and bulk density analyses were carried out using the gravity and topography data within circles with a radius of 3◦
The spatial resolution of our bulk density estimates are about a factor of two better than previous studies that used lower resoution gravity data, and this allowed us to investigate the porosity structure of lunar impact basins
Summary
High resolution data from the Gravity Recovery and Interior Laboratory (GRAIL) mission (Zuber et al, 2013a) allowed to investigate physical characteristics of the lunar interior. In combination with topography data, variations in bulk density of the lunar crust can be investigated (e.g., Besserer et al, 2014; Wieczorek et al, 2013), and when compared with independent knowledge of mineral grain densities based on remote sensing data, the porosity of crustal materials can be estimated. The main result of these studies is that the crust of the Moon exhibits high porosities, between about 4% and 21%, with an average of about 12%. While the interiors of many impact basins were found to have lower porosities, the two youngest and largest basins on the Moon, Moscoviense and Orientale, show particular high porosities in their surroundings (Wieczorek et al, 2013). In order to avoid the contribution of the gravity signal caused by the uplift of mantle material (e.g., Melosh et al, 2013; Wieczorek & Phillips, 1998), their study was restricted to complex craters with
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