China found mysterious glass spheres on the Moon. Are they a window into its past?

Glass isn't uncommon on the Moon. But these spheres are.
Ameya Paleja
File photo of the Yutu-2 roverCNSA/ Wikimedia Commons

China's Yutu-2 lunar rover on a mission to find out more about the far side of the Moon has made a startling new discovery. It has found mysterious glass spheres that may have captured within them important information about the Moon's composition and history of its impact events, Science Alert reported

Originally scheduled to be operational on the lunar surface for just three months, the Yutu-2 now holds the record of being the longest operational rover on the Moon. When it landed in 2019, it became the first rover to reach the far side of the Moon and has since been providing us insights about the side we cannot see from Earth. Last month, we learned that the soil on the far side is a lot stickier, and now there is the mystery of the glass spheres. 

There is plenty of glass on the Moon

If humanity ever went looking for glass on the surface of the Moon, it would find it aplenty. As Science Alert explains in its post, there is a lot of silicate material on the lunar surface and all that is needed to turn it into the glass is intense heat. In the past, the Moon was home to volcanic eruptions but even today, impact from smaller objects like meteorites generates sufficient heat to make glass. 

The spheres observed by Yutu-2 could likely be the result of the latter, the researchers state in their paper published in Science Bulletin. However, the lunar rover has found many such spheres during its three-year presence on the surface and yet these new spheres are something different. 

Other spheres found by Yutu-2 have been barely a millimeter in size, while these two spheres have diameters up to an inch wide (25 mm).  Interestingly, the Apollo 16 mission also found similar spheres on the near side of the Moon. In fact, at 1.5 inches in diameter, they were much bigger than the ones Yutu-2 has found. 

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So what sets these spheres apart?

According to Zhiyong Xiao and other authors of the study, the spheres found on the far side are translucent - not completely transparent and have a vitreous luster as seen on quartz or topaz, here on Earth. The spheres have been found near fresh impact craters which point towards meteorite crashes as the cause of their formation. 

The researchers, however, believe that the spheres were originally formed long ago when the Moon had volcanic eruptions and ended up being excavated during a much recent meteorite crash, were melted and reformed into translucent globs again. 

If the theory holds, then it is likely that there are many more such spheres on the lunar surface whose composition can be studied to peer into the Moon's past. If that were the case, the Chinese have quite some experience in bringing back samples from the Moon.