Geological Characteristics of Von Kármán Crater, Northwestern South Pole‐Aitken Basin: Chang'E‐4 Landing Site Region

Abstract

Von Kármán crater (diameter = ~186 km), lying in the northwestern South Pole‐Aitken (SPA) basin, was formed in the pre‐Nectarian. The Von Kármán crater floor was subsequently flooded with one or several generations of mare basalts during the Imbrian period. Numerous subsequent impact craters in the surrounding region delivered ejecta to the floor, together forming a rich sample of the SPA basin and farside geologic history. We studied in details the targeted landing region (45.0–46.0°S, 176.4–178.8°E) of the 2018 Chinese lunar mission Chang'E‐4, within the Von Kármán crater. The topography of the landing region is generally flat at a baseline of ~60 m. Secondary craters and ejecta materials have covered most of the mare unit and can be traced back to at least four source craters (Finsen, Von Kármán L, Von Kármán L', and Antoniadi) based on preferential spatial orientations and crosscutting relationships. Extensive sinuous ridges and troughs are identified spatially related to Ba Jie crater (diameter = ~4 km). Reflectance spectral variations due to difference in both composition and physical properties are observed among the ejecta from various‐sized craters on the mare unit. The composition trends were used together with crater scaling relationships and estimates of regolith thickness to reconstruct the subsurface stratigraphy. The results reveal a complex geological history of the landing region and set the framework for the in situ measurements of the CE‐4 mission, which will provide unique insights into the compositions of farside mare basalt, SPA compositional zone including SPA compositional anomaly and Mg‐pyroxene annulus, regolith evolution, and the lunar space environment.

The Moon’s farside shallow subsurface structure unveiled by Chang’E-4 Lunar Penetrating Radar

“…By analyzing the trend of the rays in the CE-2 DOM image, the distal ejecta over the CE-4 landing regions are most probably from Finsen, Von Kármán L, and several other craters (2). Table S1 shows the estimated thickness for the major ejecta-contributors at the CE-4 landing site using the ejecta thickness model, showing that ejecta thickness at the CE-4 landing site is ~8.1 m, which is comparable with that estimated by Huang et al (2).…”

“…The absolute model age of the mare basalts was dated to be ~3.6 billion years (Ga) based on the size-frequency distribution of superposed impact craters (2,14). Judging from the remote optical and multispectral images, a large portion of mare basalt was later overprinted by distal ejecta that appear bright, which were most probably delivered from surrounding large craters such as Finsen and Von Kármán L (2). As a result, secondary craters are widespread over the floor of Von Kármán, as indicated by their spatial patterns (e.g., chains or clusters with herringbone-shaped morphology) (2,15).…”

“…Judging from the remote optical and multispectral images, a large portion of mare basalt was later overprinted by distal ejecta that appear bright, which were most probably delivered from surrounding large craters such as Finsen and Von Kármán L (2). As a result, secondary craters are widespread over the floor of Von Kármán, as indicated by their spatial patterns (e.g., chains or clusters with herringbone-shaped morphology) (2,15). The CE-4 spacecraft landed on the bright distal ejecta from surrounding large craters ( Fig.…”

Mineral Abundances Inferred From In Situ Reflectance Measurements of Chang'E‐4 Landing Site in South Pole‐Aitken Basin

“…The CE-4 landing area is located within the impact-induced melt pool (Potter et al, 2012;Zhu et al, 2018). The thick impact sheet (>50 km; Potter et al, 2012;Zhu et al, 2018) produced during the impact cratering process may differentiate and form the PLG-rich but OLVand PYX-poor crust (Hurwitz & Kring, 2014;Uemoto et al, 2017;Vaughan & Head, 2014), as measured at the landing site by CE-4 on the ejecta deposits excavated from the Finsen crater (Huang et al, 2018).…”

The New Moon: Major Advances in Lunar Science Enabled by Compositional Remote Sensing from Recent Missions

“…Active attempts are being made worldwide to address some of these new questions, as well as old, unresolved questions through orbiters, landers and sample return missions (Figure 12). Several missions from national space agencies are in advanced stages of execution, including Chang'E-4 (first far side landing) and Chang'E-5 mission (sample return mission), Chandrayaan-2 (first landing at lunar high latitudes) and Lunar flashlight (multi-laser probing of the lunar poles in CubeSat architecture) (e.g., [100,[241][242][243]). Several other missions are being currently planned or have been proposed, including LunaGlob, a mission to the lavatube skylights and the magnetic anomalies (e.g., [185,188,189,244,245]).…”