Estimation of the elastic thickness over ancient Mare Moscoviense

Abstract

The Moscoviense basin is an atypical lunar impact basin with concentric rings of positive and negative gravity anomalies. This basin can provide insights into the inhomogeneous thermal activities across the farside of the Moon. Based on an updated spherical harmonic thin elastic-shell loading model, we used localized admittance analyses to estimate the elastic thickness as well as other associated selenophysical parameters for the Moscoviense basin. The high precision gravity and topography data employed in our estimation were collected by the Gravity Recovery and Interior Laboratory and the Lunar Orbiter Laser Altimeter missions. Our results indicate that the crust-mantle interface is mainly compensated by the prefilling depth rather than the observed surface topography. The results constrained within two standard deviations yielded a small load ratio (∼0.168), a best-fit crustal thickness of 36.2 km, and an optimized crustal density of 3159.5 kg m−3. Such large density approaches the density of olivine-rich mantle materials, implying that the excavation of the Mare Moscoviense occurred during a basin-forming impact. The inversed elastic thickness at Mare Moscoviense was around 18 km, lower than the previous results (∼60 km) found over Mare basins on the lunar nearside. These results indicate that extreme thermal activity existed during the Moscoviense basin-forming period such as reheating mechanisms from a double-impact process and mare volcanism.

The Ancient Lithospheric Parameters of Impact Basins on the Far Side of the Moon Based on the Mantle and Mare Basalt Load Model

“…For the Moscoviense basin, our estimation of the Te using the mantle and mare basalt load model yields a value of 10.13 km, with a lower bound of 7 km and an upper bound of 22 km. It is noteworthy that our best fit value is lower than the result reported in Zhong's research (18 km) (Zhong et al., 2019). However, the best fit elastic thickness result from Zhong is also within our optimal range.…”

“…While the far side of the moon has fewer impact basins compared to the near side, they still offer valuable insights into the lithospheric structure of the moon (Kumar et al., 2018). Investigation of these basins on the far side of the Moon can yield valuable insights into the strength of the lithosphere during its early growth stages (Zhong et al., 2019). The simplest model of the lithosphere is a thin floating elastic plate in equilibrium, and a response is generated by the lithosphere to the loads acting on it (Audet, 2014).…”

“…Consequently, in impact basin areas where the admittance and correlation spectra alternate, this method fails to accurately fit the spectra (Ding et al, 2019). Zhong et al (2019) used local admittance analysis based on an updated thin elastic shell loading model to estimate the elastic thickness (∼18 km) of the Moscoviense basin, but the uncertainty of lithospheric structural parameters was not provided. Deng, Xiao, et al (2023) and modeled mantle plugs using a global crustal thickness model, which can provide a more realistic post impact crustal structure and obtain good theoretical and observational admittance fitting results on Mercury.…”

“…In previous studies, the crustal structure before and after impact was typically inferred by analyzing topography, such as utilizing basin-scale relationships (Ding et al, 2019;Wieczorek & Phillips, 1998;Zhong et al, 2019Zhong et al, , 2022. However, it is difficult to infer the relationship between the size and shape of mantle uplift and topographic depressions shortly after the impact.…”

Lithospheric Loading Model for Large Impact Basins Where a Mantle Plug Is Present

“…In previous studies considering the infilling or/and the mantle loading in the impact basin region, post-impact and pre-infilling crustal structures were usually inferred from topography, such as using basin scaling relationships (Ding et al, 2019;Zhong et al, 2018Zhong et al, , 2019, impact simulation results (Mancinelli et al, 2015), or initial isostatic hypothesis (Ritzer & Hauck, 2009;Searls et al, 2006). Inferring the sub-surface mantle structure from the isostatic hypothesis requires information about its original basin shape and the degree of compensation (e.g., Ritzer & Hauck, 2009).…”