China’s Chang’e-4 lander made history when it completed the first-ever soft landing on the far side of the moon in January 2019. After the landing, Chang’e-4 deployed the Yutu-2 rover to explore the surface in greater detail. Now, the team has spotted some very unusual rocks scattered around Von Kármán crater that appear to be much younger than surrounding formations. This could point to previously unknown elements of the moon’s geological history.
The moon today is a static environment, but it was not always so. Most experts agree the moon formed after a large object collided with the primordial Earth. It took millions of years for the moon to cool after that, but the surface today is heavily eroded. That’s why the rocks (the “trail” to the right in the above photo) spotted last month were so perplexing.
On the moon, most rock formations have been heavily eroded over millions of years by microscopic meteorite impacts and extreme temperature change. As a result, the surface has a largely uniform color and texture. The Von Kármán crater flooded with lava several times in its past, leaving most of the area smooth and dark (a basalt patch). These objects are different — they’re lighter in color and they poke up from the surface. The shapes are similar, so it’s reasonable to assume they share an origin.
Dan Moriarty from Goddard Space Flight Center speculates that the mysterious rocks have a higher content of light materials from the lunar highlands crust. They might be “regolith breccia” that were formed by an impact in the region after the one that formed Von Kármán crater. Alternatively, they could be primary crustal rock excavated from below the surface by an impact. They could be as young as 10 million years or as old as 2 billion — we need more data to know for sure.
The Yutu-2 rover has reportedly approached the rocks to take more detailed images. It also used its Visible and Near-infrared Imaging Spectrometer (VNIS) instrument to scan the rocks. However, it completed this task on Lunar day 13, the data from which has not been released publicly yet.
China designed the Yutu-2 rover to last about three months on the moon, but it’s already well past that. The next phase of China’s lunar exploration will kick off later this year with the launch of Chang’e-5. This lander will carry a sample return vehicle that will return lunar regolith to Earth. If successful, this will be the first sample of lunar material collected since The Soviet Luna 24 mission in 1976.
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