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Small-scale density variations in the lunar crust revealed by GRAIL
J C Jansen1, J C Andrews-Hanna2, Y Li1
1Department of Geophysics, Colorado School of Mines, Golden, CO 80401.
Icarus
|September 10, 2020
Summary
The Gravity Recovery and Interior Laboratory (GRAIL) mission reveals lunar crustal density variations. These anomalies, primarily driven by porosity, offer insights into the Moon's shallow interior structure.
Area of Science:
- Planetary Science
- Geophysics
- Lunar Geology
Background:
- Gravity Recovery and Interior Laboratory (GRAIL) data show ~98% of the Moon's high-degree gravity signal correlates with topography.
- The remaining 2% of the gravity signal indicates subsurface density variations within the lunar crust.
- These anomalies are linked to small-scale, shallow density heterogeneities.
Purpose of the Study:
- To model small-scale, three-dimensional density variations in the lunar crust using gravity inversions.
- To investigate potential sources of these density anomalies, including porosity, intrusions, and compositional variations.
Main Methods:
- Gravity inversion techniques applied to GRAIL data.
- Analysis of density variations in three distinct lunar regions.
- Modeling of end-member scenarios: porosity, mafic intrusions, and bulk composition changes.
Main Results:
- Inversion results indicate shallow density variations of 100-200 kg/m³.
- Porosity changes can entirely account for observed density anomalies.
- South Pole-Aitken basin anomalies further support porosity as a primary source.
Conclusions:
- While porosity appears to be the dominant factor, mafic intrusions and compositional variations also contribute to lunar crustal density heterogeneity.
- The lunar crust exhibits significant density variations (±10%) across multiple scales, from centimeters to hundreds of kilometers.
- Integrated analysis of GRAIL data with remote sensing and sample studies provides a comprehensive view of lunar crustal density.
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