Tides on the Moon: Theory and determination of dissipation. Issue 4 (15th April 2015)

• Record Type: Journal Article
• Authors: Williams, James G.; Boggs, Dale. H.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 4(2015:Apr.)
• Page Start: 689
• Page End: 724
• Publication Date: 2015-04-15
• Subjects: Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1002/2014JE004755
• Languages: English
• ISSNs: 2169-9097

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Solid body tides on the Moon vary by about ±0.1 m each month. In addition to changes in shape, the Moon's gravity field and orientation in space are affected by tides. The tidal expressions for an elastic sphere are compact, but dissipation introduces modifications that depend on the forcing period. Consequently, a Fourier representation of the tide‐raising potential is needed. A mathematical model for the distortion‐caused tidal potential may be used for the analysis of precise spacecraft tracking data. Since tides affect gravitational torques on the Moon from the Earth's attraction, the lunar orientation is also affected. Expressions for five periodic perturbations of orientation are presented. The rheological properties of lunar materials determine how the Moon responds to different tidal periods. New lunar laser ranging solutions for the tidal orientation terms are presented. The quality factor <italic>Q</italic> is 38 ± 4 at 1 month, 41 ± 9 at 1 year, ≥74 at 3 years, and ≥58 at 6 years. The ranging results can be matched with absorption band models that peak at ~120 days and single relaxation time models that peak at ~100 days. Combined models are possibilities. Dissipation can modify laser ranging solutions; previously reported core flattening is too uncertain to be useful. Strong lunar tidal dissipation, modeled to arise in the deep hot mantle, appears to be from a region with radius ≥535 km. Classical Maxwell‐type dissipation is too weak to detect at 3 and 6 year periods.</p> </abstract>