On the far side of the Moon, China's Yutu-2 mission has made another fascinating discovery. The panoramic camera picked out two small intact spheres of translucent glass while listening to the dry, gray dust.
The composition of the Moon's mantle and impact events can be recorded. Natural lunar marbles could be important research targets in the future.
On the Moon, glass is not uncommon. Both of those ingredients are readily available on the Moon, and the material forms when silicate material is subjected to high temperature.
The formation of volcanic glass can be traced back to volcanism and impacts from smaller objects such as meteorites.
A team of scientists led by planetary geologist Zhiyong Xiao of Sun Yat-sen University and the Chinese Academy of Sciences theorize that the spherules observed by Yutu-2 could be behind the latter.
Most of the glass found on the Moon looks different from what Yutu-2 found. Spherules are plentiful, but they are less than a millimeter in size.
During an impact, tiny glass spherules are created that create intense heat that causes the crust to melt and spray into the air. The molten material falls down as glass beads.
The spherules of Yutu-2 are 25 to 15 millimeters across. Glass balls up to 40 millimeters across were recovered from the Moon's near side during the Apollo 16 mission. These are thought to be impact spherules, and were traced to a nearby crater.
There are differences between the two discoveries. Xiao and his colleagues explain that the far side spherules seem to be translucent or semi- transparent. They found four more spherules that had the same luster, but their translucency was not confirmed.
The spherules were found near impact craters, which could suggest that they were formed during lunar meteorite impacts, although it is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556
The team believes that the most likely explanation is that they formed from volcanic glass called anorthosite that melted again on impact.
The researchers write in their paper that the peculiar geometry and local context of the glass are consistent with being anorthositic impact glasses.
The objects on the lunar surface could be similar to the tektites, which are pebble-sized glassy objects that form when Earth material melts, sprays into the air, and hardens and forms into a ball as it falls back down.
If they are lunar tites, they might be common on the lunar surface. The team says that this offers some intriguing possibilities for future research.
As the first discovery of glass on the Moon, this study predicts that it should be abundant across the lunar highland, providing promising sampling targets to reveal the early impact history of the Moon.
The paper detailing the discovery has been published.
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