China’s lunar rover has spotted something incredible: A pair of glass globules that are significantly larger than glass beads that are usually found on the Moon's surface, and they also happen to be translucent, which is yet another interesting feature. Now, the lunar regolith is no alien to glass-like substances, which were created as a result of volcanism and high-velocity impact from objects that hit the Earth's sole natural satellite in the past.

When a high-velocity object like an asteroid hits the lunar surface, the impact leads to a burst of high temperature that melts some of the lunar material around it, which eventually cools down and takes a glassy appearance. However, condensation of impact vapor can also lead to the formation of glass. Earlier this year, the rover also discovered a green gel-like material that is thought to have originated from impact melt breccia.

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Continuing its hot streak, the Yutu-2 rover has now sent photos of two translucent glass globules that it spotted on the moon. Glassy material on the moon is usually found over basaltic rocks or in the form of spheres that are smaller than 1 millimeter in diameter, while a majority of them measure about 300 microns on average. The spheres spotted by Yutu-2’s onboard panorama camera are of centimeter scale. In addition to spherical glass globules, the rover has also spotted dumbbell-shaped glass objects that have a light brownish color, but those need more observation data to confirm. As per the mission report, glass globules of that size haven’t been observed on the Moon so far. Moreover, the color science of these glasses is different. The findings have been published in Science Bulletin.

Catching Lunar History From Within Glass

Orange soil near Station 4 on Apollo 17
Orange soil near Station 4 on Apollo 17 (Credit: NASA)

Apollo mission astronauts also brought back glass spheres from the moon, but they were almost opaque in color with a dark green tinge. Astronaut and geologist Harrison Schmitt actually noticed these colorful glass beads while walking on the moon as part of the Apollo 17 mission in 1972. The colors varied based on the chemical composition of each spherule. These beads were also responsible for imparting an orange hue to the lunar soil as seen in photographs. In fact, scientists actually spotted water molecules in these glass beads over a decade ago, shedding more light on a supposedly watery past of the Moon. Interestingly, the Yutu-2 rover also photographed a rabbit-shaped rock recently, which was initially thought to be a mystery hut on the dark side of the moon.

Based on initial observation, the team monitoring the Yutu-2 mission notes that the large glass beads may have been originated in an impact event. And since high-energy melt is a fairly common material discovered at impact sites on Moon, the team hopes that they’ll come across more such glass beads in other craters. Unfortunately, the glass beads were photographed as the rover was just passing by. No compositional examination was done to analyze their chemistry. However, the transparent glassy objects (roughly four centimeters in size) seen by the Yutu-2’s camera are now potential sampling targets for future missions and will help understand the volcanic or impact history of that particular region on the moon.

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Source: Science Bulletin, NASA