Three-dimensional density structure of the lunar upper lithosphere

Details Three-dimensional density structure of the lunar upper lithosphere Three-dimensional density structure of the lunar upper lithosphere

Dec 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p13d1700l&link_type=abstract

American Geophysical Union, Fall Meeting 2011, abstract #P13D-1700

Other

[1221] Geodesy And Gravity / Lunar And Planetary Geodesy And Gravity, [5417] Planetary Sciences: Solid Surface Planets / Gravitational Fields, [5430] Planetary Sciences: Solid Surface Planets / Interiors

Scientific paper

The lithosphere of the Moon has a thickness over 1200 km according to the seismology studies. It records the giant impact events during the processes of solidification. The upper lithosphere including the crust and the upper mantle was thought to be a nonuniform layer in thickness and seismic velocity, yet the lateral density structure remains poorly understood. The global gravity data thus provides a significant constraint on the three-dimensional (3-D) density structure of the Moon. Previous studies assumed that the crust and the mantle have constant density the gravity anomalies are only produced by the variations of interface between the crust and the mantle. Therefore, the constant density may give overestimation or underestimation of the Moho depth. In contrast, we apply a 3-D inverse method in spherical coordinate to the lunar gravity anomaly. It is a direct way in recovering the density structures beneath mascon basins or the lateral density heterogeneities in the upper lithosphere. The gravity anomaly we use in this study is the Bouguer gravity anomaly calculated at 1750 km radius relative to the reference radius, 1737.153 km[1], from the newly gravity field model SGM100i[2] and the topography model LRO_LTM02[1]. In order to understand the global feature of density variation, we truncate the long wavelength anomaly up to the order of 30 to reconstruct the density distribution above the depth of 100 km in the Moon. With the inverse technique, we obtain a global 3-D density structure of the lunar lithosphere down to 100 km depth. The major features are dominated by the mascons with dense materials and the broad region of the farside highland with relative low density mass. From this structure, the huge mass concentrations are found beneath the South Pole-Aitken (SPA) basin, meaning that the oblique impact not only excavated the SPA basin into deep but also made the mantle uplifted close to a depth of 30 km (relative to a 1738 km radius). We suggest here that the lunar Moho interface approaches to the surface, and the mantle materials may be exposed in some areas. In other words, the crustal thickness may be overestimated in the previous studies. This research is supported by the Special Fund for Basic Scientific Research of Central Colleges, China University of Geosciences (Wuhan) (No. CUG100701 and CUG090106), and the National Natural Science Foundation of China (Grant No. 40774060). [1] Smith D E, Zuber M T, Neumann G A, et al. Initial observations from the Lunar Orbiter Laser Altimeter (LOLA). Geophysical Research Letters, 2010, 37: L18204. [2] Goossens S.; Matsumoto K.; Liu Q.; et al. Lunar gravity field determination using SELENE same-beam differential VLBI tracking data. Journal of Geodesy, 2010, 85(4): 205-228.

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