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- Title
Comparison of the Effects of Different Viscoelastic and Temperature Models on the Theoretical Tidal Response of the Moon.
- Authors
Xiao, Chi; Wu, Yunlong; Yan, Jianguo; Harada, Yuji; Zhang, Yi; Li, Fei
- Abstract
The existence of an attenuating layer that is partially molten at the bottom of the lunar mantle has long been debated, mainly because different viscoelastic models yield varying interpretations. Through a combination of different viscoelastic and temperature models, we study the theoretical tidal response of the Moon. As viscoelastic models, we consider the Maxwell, Burgers, Andrade, and Sundberg‐Cooper model, where the Burgers and Andrade models each comprise two different scenarios. Determining which viscoelastic model is most suitable for the Moon is difficult since more than one combination of viscoelastic and temperature models satisfies the observed period dependence of the lunar tidal quality factor Q. Further inversion reveals that most viscoelastic models potentially satisfy the monthly observations of the Moon; however, only the Maxwell and Andrade models satisfy the period‐dependent Q while remaining consistent with the observed tidal Love numbers k2 and h2. We ultimately suggest that the Andrade model with β = μα−1η−α, where α and β are the empirical parameters, μ is unrelaxed shear modulus, and η is viscosity, is more suitable for the Moon because the Maxwell model underestimates the mantle viscosity and the viscous dissipation at short periods. Based on our model assumptions and the currently available observations, a partially molten layer with a grain size on the order of 10–100 µm, in which the temperature changes drastically may exist at the bottom of the lunar mantle. Plain Language Summary: Whether the lowermost lunar mantle is partially molten, meaning that a small portion of solid mineral has melted, is still debated. In this study, we attempt to investigate this issue using the observations of lunar tidal parameters. The tidal parameters, which characterize the tidal response in the lunar surface raised by the gravity of celestial bodies, such as the Earth, are related to the deep interior structure. We calculate the synthetic tidal parameters of different models and compare them to the observed data. We find a model which is most appropriate for describing the tidal response of the Moon among these models examined hereof. In addition, we provide evidence for a partially molten layer at the base of the lunar mantle. Key Points: We study the viscoelastic behavior of the Moon using different combinations of viscoelastic and temperature modelsThe Andrade model is a more suitable viscoelastic model than Maxwell, Burgers, and Sundberg‐Cooper when applied to the MoonCurrent observations support the existence of a partially molten layer at the bottom of the lunar mantle when applying the Andrade model
- Subjects
OBSERVATIONS of the Moon; MODULUS of rigidity; HARD rock minerals; QUALITY factor; LUNAR surface; MOON; TEMPERATURE
- Publication
Journal of Geophysical Research. Planets, 2022, Vol 127, Issue 12, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2022JE007215