The penetrating radar aboard the Chang’E-4 rover is revealing layers of the moon’s history
Image taken by the Panoramic Camera (PCAM) on board the Chinese lunar module Yutu 2 as it looks at the Chang’e 4 lander. Credit: Nature Communications (2019). DOI: 10.1038/s41467-019-12278-3/wikimedia commons/CC BY-SA
A team of astronomers at the Planetary Science Institute, working with colleagues from the Chinese Academy of Sciences, the University of Shenzhen and the University of Aberdeen, used data from China’s Chang’E-4 spacecraft to learn more about the history of the moon. In their study, reported in Journal of Geophysical Research: PlanetsThe group analyzed satellite penetrating radar (LPR) data sent back from the spacecraft.
China’s Chang’E-4 spacecraft has been wandering on the far side of the moon since 2018. As it zigzags, it has been sending radio signals downward with its LPR instrument. The same device detects and records the signals returned, which is a form of radar. Three years ago, another team of researchers used a subset of the same data to create a subsurface map that extends 40 meters below the surface. In this new paper, the research team builds on that effort, creating a subsurface map that extends 300 meters below the surface.
The research team found that the top 300 meters of the moon’s surface consists of several layers of material, some broken rocks, some dust and some soil. The researchers have also found evidence of a hidden crater. Beneath that, they found layers of lava, evidence of the moon’s volcanic past.
Previous research indicated that the moon formed about 4.5 billion years ago, and is believed to have arisen when a large planet collided with Earth, hurling a portion of the combined planetary matter into its orbit. Previous research also indicated that later on, a large object hit the moon, cracking its surface. This allowed some of the magma to seep to the surface.
Data from Chang’E-4 support this theory. In analyzing the lava layers, they found that each subsequent layer was thinner than the previous one, which is evidence of cooling and crack closing. And previous research had indicated that volcanic activity stopped on the moon nearly a billion years ago, and it is now considered geologically dead.
The researchers note that Chang’E-4 is still sending and listening in radio signals, which means there’s still more to learn.
more information:
Jianqing Feng et al., Stratified structures in the upper lunar part several hundred meters along the first 1,000-meter traversal of the Chang’E-4 rover, Journal of Geophysical Research: Planets (2023). doi: 10.1029/2022JE007714
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