Scientists have spotted a pair of large translucent glass spheres in images from the Yutu-2 spacecraft - most likely the result of a recent meteorite impact.
The Yutu-2 lunar rover (Yutu-2) is part of the Chang'e 4 mission, which has been operating on the back side of the Moon since 2019 and regularly reminds us of itself by detecting unexpected and unusual objects. Another - and perhaps the most important - such find was a pair of small, translucent glass spheres. The first mentions of it appeared a few days ago, and now Science Bulletin magazine has published a detailed article about the event.
There is no great mystery about the find: as Zhiyong Xiao and his co-authors suggest, the balls were most likely formed in a meteorite impact or as a result of volcanic activity that persisted in the early eras of the moon. Suffice it to recall that the moonwalker operates in the 186-kilometre Von Karman crater, which itself is located in the huge (about 2500 kilometres) South Pole-Aitken impact basin and is surrounded by other impact craters.
Glass spheres have been found on the Moon many times before but they are mostly tiny, turbid particles in the local regolith. These same spheres are rather large (1.5-2.5 centimetres in diameter) - almost like the samples found by the Apollo 16 astronauts. Unlike those spheres, the ones found on the back side of the Moon are almost transparent.
Scientists are particularly interested in these spheres as they are believed to contain valuable information about the composition and past of the moon. Some images taken by Yutu-2 show other similar objects nearby, although the resolution of the camera is not sufficient to identify them reliably.
This 'scattering' of glass appears to have been produced by a meteorite impact, which instantly melted the silicon minerals and scattered the droplets away. In flight, they quickly solidified, retaining their spherical shape, as happens with tektites on Earth. It does not seem to have happened very long ago.
The authors of the article note that over a hundred thousand years, the lunar regolith covers objects in a layer of a few centimeters, but these balls were lying directly on the surface. They either appeared recently or have recently been brought out of the depths.
