CaltechAUTHORS
Published July 2014 | Version Published
Journal Article Open

Lunar interior properties from the GRAIL mission

Creators

  • 1. ROR icon Jet Propulsion Lab
  • 2. ROR icon Goddard Space Flight Center
  • 3. ROR icon University of Maryland, Baltimore
  • 4. ROR icon University of California, Santa Cruz
  • 5. ROR icon Marshall Space Flight Center
  • 6. ROR icon Purdue University West Lafayette
  • 7. ROR icon Southwest Research Institute
  • 8. ROR icon Massachusetts Institute of Technology
  • 9. ROR icon Lamont-Doherty Earth Observatory
  • 10. ROR icon Carnegie Institution for Science
  • 11. ROR icon Institut de Physique du Globe de Paris
  • 12. ROR icon Colorado School of Mines
  • 13. ROR icon Brown University
  • 14. ROR icon Lunar and Planetary Institute
  • 15. ROR icon University of Arizona
  • 16. ROR icon University of Hawaii at Manoa

Abstract

The Gravity Recovery and Interior Laboratory (GRAIL) mission has sampled lunar gravity with unprecedented accuracy and resolution. The lunar GM, the product of the gravitational constant G and the mass M, is very well determined. However, uncertainties in the mass and mean density, 3345.56 ± 0.40 kg/m³, are limited by the accuracy of G. Values of the spherical harmonic degree-2 gravity coefficients J₂ and C₂₂, as well as the Love number k₂ describing lunar degree-2 elastic response to tidal forces, come from two independent analyses of the 3 month GRAIL Primary Mission data at the Jet Propulsion Laboratory and the Goddard Space Flight Center. The two k₂ determinations, with uncertainties of ~1%, differ by 1%; the average value is 0.02416 ± 0.00022 at a 1 month period with reference radius R = 1738 km. Lunar laser ranging (LLR) data analysis determines (C − A)/B and (B − A)/C, where A < B < C are the principal moments of inertia; the flattening of the fluid outer core; the dissipation at its solid boundaries; and the monthly tidal dissipation Q = 37.5 ± 4. The moment of inertia computation combines the GRAIL-determined J₂ and C₂₂ with LLR-derived (C − A)/B and (B − A)/C. The normalized mean moment of inertia of the solid Moon is Iₛ/MR² = 0.392728 ± 0.000012. Matching the density, moment, and Love number, calculated models have a fluid outer core with radius of 200–380 km, a solid inner core with radius of 0–280 km and mass fraction of 0–1%, and a deep mantle zone of low seismic shear velocity. The mass fraction of the combined inner and outer core is ≤1.5%.

Additional Information

M. Efroimsky commented on tides and dissipation. K. Matsumoto and S.-C. Han provided information on their separate solutions. The GRAIL mission is a component of the NASA Discovery Program under contract to the Massachusetts Institute of Technology. The lunar laser ranging efforts at the McDonald Observatory, Observatoire de la Côte d'Azur, and Apache Point Observatory provided data that are archived by the International Laser Ranging Service at http://www.iers.org/IERS/EN/Organization/TechniqueCentres/ILRS/ilrs.html. A portion of the research described in this paper was carried out at the Jet Propulsion Laboratory of the California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

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Additional details

Identifiers

Eprint ID
119695
Resolver ID
CaltechAUTHORS:20230307-22002000.15

Related works

Describes
10.1002/2013JE004559 (DOI)

Funding

NASA/JPL/Caltech

Dates

Created
2023-03-08
Created from EPrint's datestamp field
Updated
2023-03-08
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