Determination of the lunar body tide from global laser altimetry data

Abstract

We use global data from the Lunar Orbiter Laser Altimeter (LOLA) to retrieve the lunar tidal Love number $$h_2$$ h 2 and find $$h_2 = 0.0387\pm 0.0025$$ h 2 = 0.0387 ± 0.0025 . This result is in agreement with previous estimates from laser altimetry using crossover points of LOLA profiles. The Love numbers $$k_2$$ k 2 and $$h_2$$ h 2 are key constraints on planetary interior models. We further develop and apply a retrieval method based on a simultaneous inversion for the topography and the tidal signal benefiting from the large volume of LOLA data. By the application to the lunar tides, we also demonstrate the potential of the method for future altimetry experiments at other planetary bodies. The results of this study are very promising with respect to the determination of Mercury’s and Ganymede’s $$h_2$$ h 2 from future altimeter measurements.

Global Drivers and Transport Mechanisms of Lunar Rockfalls

“…We observe that regions with large radial tidal displacement values can feature an increased number of rockfalls (Figure 4). Currently, tidal forces can only be mapped on large spatial scales (e.g., Thor et al, 2021) and we are not able to observe the same trend in all studied geographic regions, meaning that our observations are not entirely conclusive. Tidally driven, cyclic, and vertical displacements of the lunar crust on the order of tens of centimeters could, in theory, favor fracture growth, weathering, and erosion in general, resulting in more rockfall events on average.…”

“…These two maps have a spatial resolution of ∼2,000 m/pixel. Additionally, we utilize maps of estimated lunar radial tidal displacements generated by Thor et al (2021), which is based on LOLA altimetry data that has been processed to retrieve vertical surface displacements (tides), and of nightside surface albedo (Lyman-α wavelength bands), which is based on Lyman Alpha Mapping Project (LAMP) far-ultraviolet data (e.g., Gladstone et al, 2012). The latter has a spatial resolution of ∼1,000 m/pixel.…”

Comparison of the Effects of Different Viscoelastic and Temperature Models on the Theoretical Tidal Response of the Moon

“…For simplicity, we follow the assumptions of previous studies (e.g., Matsumoto et al., 2015; Tan & Harada, 2021) that the observed value of k 2 is at a monthly period. For the second‐degree Love number h 2 , the real part of h 2 obtained from an analysis of the LLR data was Re( h 2 ) = 0.0473 ± 0.0061(Williams & Boggs, 2015) with a modeled monthly value of 0.0423; however, a much smaller value of h 2 = 0.0387 ± 0.0025 was obtained from the Lunar Orbiter Laser Altimeter (LOLA) (Thor et al., 2021).…”

“…For the second-degree Love number h 2 , the real part of h 2 obtained from an analysis of the LLR data was Re(h 2 ) = 0.0473 ± 0.0061 (Williams & Boggs, 2015) with a modeled monthly value of 0.0423; however, a much smaller value of h 2 = 0.0387 ± 0.0025 was obtained from the Lunar Orbiter Laser Altimeter (LOLA) (Thor et al, 2021).…”

Is there a semi-molten layer at the base of the lunar mantle?

“…The former has been derived from GRAIL mission tracking data and, as with k 2 above, we adopt the unweighted average of the two existing independent solutions (Lemoine et al, 2013;Konopliv et al, 2013): k 3 = 0.0081 ± 0.0018. The latter has been measured by LLR and by laser altimetry (Mazarico et al, 2014;Pavlov et al, 2016;Viswanathan et al, 2018;Thor et al, 2021), the most recent value, presented by Thor et al (2021), being h 2 = 0.0387±0.0025.…”