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Evidence for a past high-eccentricity lunar orbit.
Ian Garrick-Bethell1, Jack Wisdom, Maria T Zuber
1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. iang@mit.edu
Science (New York, N.Y.)
|August 5, 2006
Summary
Past high-eccentricity orbits explain the Moon's mysterious moment of inertia differences. This suggests a dynamic lunar history and impacts our understanding of its early thermal evolution.
Area of Science:
- Lunar Science
- Planetary Dynamics
- Astrophysics
Background:
- The Moon's unequal principal moments of inertia, noted by Laplace in 1799, remain a significant mystery in lunar science.
- These differences are reflected in the Moon's low-order gravity field and libration parameters.
Purpose of the Study:
- To investigate how past high-eccentricity orbits could explain the observed differences in the Moon's principal moments of inertia.
- To explore the implications of these findings for the Moon's dynamical history and early thermal evolution.
Main Methods:
- Performed calculations to model the effects of past orbital configurations on lunar moments of inertia.
- Investigated potential orbital resonances, such as a 3:2 spin-orbit resonance similar to Mercury's.
Main Results:
- Calculations demonstrate that past high-eccentricity orbits can account for the Moon's moment differences.
- A possible past 3:2 resonance of the Moon's orbit period to its spin period was identified as a viable solution.
Conclusions:
- Past high-eccentricity orbits offer a compelling explanation for the Moon's moment of inertia anomalies.
- The Moon's dynamical history may be richer than previously assumed, influencing models of its early thermal evolution.
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