Density Structure of the Von Kármán Crater in the Northwestern South Pole-Aitken Basin: Initial Subsurface Interpretation of the Chang'E-4 Landing Site Region.

Chikondi Chisenga,Jiannan Zhao,Jean-Pierre Barriot,Qingyun Deng,Jianguo Yan

doi:10.3390/s19204445

Abstract

The Von Kármán Crater, within the South Pole-Aitken (SPA) Basin, is the landing site of China’s Chang’E-4 mission. To complement the in situ exploration mission and provide initial subsurface interpretation, we applied a 3D density inversion using the Gravity Recovery and Interior Laboratory (GRAIL) gravity data. We constrain our inversion method using known geological and geophysical lunar parameters to reduce the non-uniqueness associated with gravity inversion. The 3D density models reveal vertical and lateral density variations, 2600–3200 kg/m3, assigned to the changing porosity beneath the Von Kármán Crater. We also identify two mass excess anomalies in the crust with a steep density contrast of 150 kg/m3, which were suggested to have been caused by multiple impact cratering. The anomalies from recovered near surface density models, together with the gravity derivative maps extending to the lower crust, are consistent with surface geological manifestation of excavated mantle materials from remote sensing studies. Therefore, we suggest that the density distribution of the Von Kármán Crater indicates multiple episodes of impact cratering that resulted in formation and destruction of ancient craters, with crustal reworking and excavation of mantle materials.

Highlights

The Von Kármán Crater is a pre-Nectarian crater with a diameter of ~186 km [1] within the largest known impact structure on the farside of the Moon, the South Pole-Aitken (SPA) Basin (Figure 1) [2].The SPA is the oldest impact basin with a well-preserved impact history, which suggests that the earliest lunar history and processes related to impact cratering can be studied from it [3,4]
We performed a 3-D inversion of the Gravity Recovery and Interior Laboratory (GRAIL) gravity data to produce a density model of the
Our results reveal that the region is underlain by a mass excess anomaly beneath the Von Kármán M Crater with a density of ~3200 kg/m3, on the southern rim of the Von Kármán basin

Summary

Introduction

The Von Kármán Crater is a pre-Nectarian crater with a diameter of ~186 km [1] within the largest known impact structure on the farside of the Moon, the South Pole-Aitken (SPA) Basin (Figure 1) [2].The SPA is the oldest impact basin with a well-preserved impact history, which suggests that the earliest lunar history and processes related to impact cratering can be studied from it [3,4]. The SPA is subdivided into four distinct compositional zones [4], with the Von Kármán Crater situated within the Mg-Pyroxene Annulus zone. The Von Kármán Crater is further characterized by a Sensors 2019, 19, x FOR PEER REVIEW of 18 very thin crust with an average of 10 km [7]. It shows evidence of differentiated impact melts during itsof formation [3], low crater-floor elevation with[3], an average of 5926 m [2], relative to evidence differentiated impact melts during itsvalues formation low crater-floor elevation values awith mean lunar radius of [8]

Methods

Discussion

Conclusion