Finsen crater on the moon’s far side is 3.5 billion years old

Geologic age of Finsen Crater.

According to the study conducted by the Chinese Academy of Sciences (CAS), the absolute model age (AMA) or geologic age of Finsen crater on the moon’s far side is about 3.5 billion years (Ga). Scientists determined the Geologic age of Finsen Crater based on the crater counting method.

China’s Chang’e-4 probe, including a lander and a rover, successfully touched landed on the Von Kármán crater within the South Pole-Aitken (SPA) basin side of the moon on January 3, 2019. Since then, Chang’e-4 rover has been traversing on Von Kármán crater’s floor and has carried out a string of in situ measurements with equipped scientific payloads.

Based on this model age, scientists estimated the Chang’e-4 landing site’s regolith growth rate and the crater degradation rate within the Finsen crater.

Scientists used Chang’e-2 digital orthophoto map (DOM) and digital elevation model (DEM) data. They outlined a flat and homogenous area on the floor of Finsen as a crater count area and manually mapped craters in the outlined area.

By fitting the obtained crater size-frequency distribution (CSFD) to standard lunar cratering chronology, scientists were able to determine the AMA of Finsen crater. Both cumulative and differential fits revealed an AMA of ~3.5 Ga, indicating Finsen crater was Imbrium-aged.

Based on the thickness estimation of the Finsen crater ejecta-sourced fine-grained regolith at Chang’e-4 landing site (~12 m), the landing site’s average regolith growth rate is estimated to be about 3.4 m/Gyr.

The current depths of 25 largest craters on the Finsen crater floor were calculated by the profile-average-depth method. The estimated crater degradation rate within Finsen was about 21 ± 3 m/Gyr.

This degradation rate has the same order of magnitude to that on the lunar maria (about 32 m/Gyr), indicating lunar craters might have a similar degradation rate on a global scale.

The study was conducted by a research team led by Prof. Di Kaichang from the State Key Laboratory of Remote Sensing Sciences, Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences (CAS).

Journal Reference:
  1. Sheng Gou et al. Absolute model age of lunar Finsen crater and geologic implications, Icarus (2020). DOI: 10.1016/j.icarus.2020.114046

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