The moon hasn’t had it easy over the years. Since the dawn of the solar system 4.5 billion years ago, its gray and lifeless surface has been repeatedly pummeled by incoming space rocks, leaving behind a pockmarked landscape strewn with rubble. Beneath this surface, however, hide the moon’s most tantalizing secrets for human explorers, from possible reservoirs of ice for producing potable water and rocket fuel to hollow lava tubes that are suitable for harboring habitats. More fundamentally, mapping the moon’s subsurface can reveal otherwise-hidden epochs of solar system history written by impacts, buried craters and associated debris—as demonstrated by fresh results from a Chinese rover on the little-explored lunar far side.

In a paper published in the journal Science Advances today, a collaboration of Chinese and European researchers describes the latest results from the Chang’e-4 mission, run by the China National Space Administration. Launched in December 2018 and reaching the moon in early January 2019, the mission became the first to land on the far side of the natural satellite, targeting an intriguing region near the lunar south pole called the South Pole–Aitken Basin. Formed 3.9 billion years ago and stretching some 2,500 kilometers across, it is the biggest impact basin in the solar system—and perhaps a key to understanding how great impacts have shaped Earth and other inner planets. The Chang’e-4 rover is still operational today and has been slowly trundling across this region, traveling a few hundred meters since it landed.

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