Density and porosity of the lunar crust from gravity and topography

Huang, Qian; Wieczorek, M. A.

doi:10.1029/2012je004062

Cited by 85 publications

(80 citation statements)

References 63 publications

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“…Although the depth dependence of porosity is not well constrained, it must extend at least several kilometers below the surface and perhaps into the upper mantle. These high porosities are almost certainly a result of fractures generated by billions of years of impact cratering and are consistent with impact-induced porosities associated with small impact craters on Earth (see also Huang and Wieczorek, 2012).…”

Section: The Moonsupporting

confidence: 53%

Gravity and Topography of the Terrestrial Planets

Wieczorek¹

2015

Treatise on Geophysics

134

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Section: The Moonsupporting

confidence: 53%

Gravity and Topography of the Terrestrial Planets

Wieczorek¹

2015

Treatise on Geophysics

134

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“…In order to make progress on inverting for the thickness of the mare, it was found necessary to set one or more of these parameters to fixed values based on a priori information. To start, we made use of a mare basalt grain density map, estimated from Lunar Prospector gamma‐ray spectrometer iron and titanium abundances [ Prettyman et al , ], along with an empirical density‐composition relation based on petrological considerations from Huang and Wieczorek []. We assumed a bulk porosity of 6% (which reduces the density by the same factor) and also considered a higher value of 12%, which is the porosity of the upper highland crust derived from GRAIL gravity data [ Wieczorek et al , ].…”

Section: Resultsmentioning

confidence: 99%

“…As shown in Figure , the model contains a constant thickness layer of dense mare basalts overlying less dense highland materials. For the upper mare layer, we assume that the density of the basalts does not vary with depth, and the bulk density is calculated using an assumed constant porosity along with the grain density derived from remote sensing and petrological considerations [ Huang and Wieczorek , ]. For the highland layer, we assume that the density increases linearly with depth due to the reduction of porosity with depth [ Besserer et al , ], reaching a maximum value where the porosity is zero.…”

Section: Methodsmentioning

confidence: 99%

Thicknesses of mare basalts on the Moon from gravity and topography

et al. 2016

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A new method of determining the thickness of mare basalts on the Moon is introduced that is made possible by high‐resolution gravity data acquired from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission. Using a localized multitaper spherical‐harmonic analysis, an effective density spectrum is calculated that provides an estimate of the average crustal density as a function of spherical harmonic degree. By comparing the observed effective density spectrum with one generated from a theoretical model, the thickness of mare basalts can be constrained. We assume that the grain density of the basalts is known from remote sensing data and petrologic considerations, we assign a constant porosity to the basalts, and we let both the thickness of the basalts and the density of the underlying crust vary. Using this method, the total thickness of basalts was estimated on the nearside hemisphere, yielding an average of 0.74 km with 1σ upper and lower bounds of 1.62 km and 100 m, respectively. The region of Marius Hills, which is a long‐lived volcanic complex, is found to have the thickest basalts, with an average of 2.86 km and 1σ limits of 3.65 and 1.02 km, respectively. The crust beneath the Mare Imbrium basalts is found to have an atypically high density of about 3000 kg m−3 that we interpret as representing a mafic, unfractured, impact melt sheet.

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“…1). At half wavelengths greater than ~68 km, the correlation between topography and gravity is weak (Wieczorek et al, 2006) due to the effects of crustal thickness variations (Neumann et al, 1996;Wieczorek and Phillips, 1998;Namiki et al, 2009;Huang and Wieczorek, 2012;Wieczorek et al, 2013;Zuber et al, 2013b), mascon loading (AndrewsHanna, 2013; Melosh et al, 2013;Freed et al, 2014), and lithospheric flexure. These longwavelength signals are commonly inverted for global crustal thickness modeling, where the assumption is made that the crust of the Moon is characterized by either a constant density or by long-wavelength variations in regional density (Wieczorek et al, 2006;Wieczorek et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Small-scale density variations in the lunar crust revealed by GRAIL

Jansen

Andrews-Hanna

et al. 2017

Icarus

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Data from the Gravity Recovery and Interior Laboratory (GRAIL) mission have revealed that ~98% of the power of the gravity signal of the Moon at high spherical harmonic degrees correlates with the topography. The remaining 2% of the signal, which cannot be explained by topography, contains information about density variations within the crust. These high-degree Bouguer gravity anomalies are likely caused by small-scale (10's of km) shallow density variations. Here we use gravity inversions to model the small-scale three-dimensional https://ntrs.nasa.gov/search.jsp?R=20170003155 2019-06-07T05:41:52+00:00Z 2 variations in the density of the lunar crust. Inversion results from three non-descript areas yield shallow density variations in the range of 100-200 kg/m 3 . Three end-member scenarios of variations in porosity, intrusions into the crust, and variations in bulk crustal composition were tested as possible sources of the density variations. We find that the density anomalies can be caused entirely by changes in porosity. Characteristics of density anomalies in the South PoleAitken basin also support porosity as a primary source of these variations. Mafic intrusions into the crust could explain many, but not all of the anomalies. Additionally, variations in crustal composition revealed by spectral data could only explain a small fraction of the density anomalies. Nevertheless, all three sources of density variations likely contribute. Collectively, results from this study of GRAIL gravity data, combined with other studies of remote sensing data and lunar samples, show that the lunar crust exhibits variations in density by ±10% over scales ranging from centimeters to 100's of kilometers.

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Density and porosity of the lunar crust from gravity and topography

Cited by 85 publications

References 63 publications

Gravity and Topography of the Terrestrial Planets

Gravity and Topography of the Terrestrial Planets

Thicknesses of mare basalts on the Moon from gravity and topography

Small-scale density variations in the lunar crust revealed by GRAIL

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