Last week, images captured by China’s ‘Yuta-2’ lunar rover were returned to Earth, and were shown to display small spheres of translucent glass, dubbed ‘lunar glass’, located on the dark side of the moon. 


The Yuta-2 rover was launched in late 2018, and landed with the Chang’e-4 spacecraft on the 3rd of January, 2019. This was the fourth mission from China to the moon, and the second that involved launching a rover on the surface. Since its arrival, the solar-powered rover has been crossing the 115 mile wide Von Kármán crater located on the dark side of the moon, and is the only rover to have soft landed and explored the crater. This is not the first time that Yuta-2 has been involved in the discovery of odd lunar features during its exploration, as in 2019 it detetected an unknown green gel-like substance on the moon’s surface that has since gone unidentified by researchers. Last year, it also returned images of a ‘mystery hut’ on the horizon, which was later identified to be simply a large rock. 


The latest developments in information from the Yuta-2 rover are surrounding the most recent set of images which depict two small spheres of glass. Small pieces of lunar glass are often detected in images, and pieces of similar glass have been returned to Earth through NASA’s Apollo missions during the 1960s and 70s, but a spherule of glass is yet to be collected. Other images of similar spheres show them to be less than 3mm in diameter, but in contrast the new spheres appear to be between 2-3cm in diameter. The larger spheres are also darker in colour and opaque, whereas older images are often translucent or transparent. This contrast is rare as spheres this large have never been caught in images before, so it opens the door to even larger spheres existing on the surface that are yet to be detected. 


While the composition of the spheres remains unknown, as the current rover is not equipped to collect sufficient samples, they are most likely made of silicon and other rock forming materials. Glass deposits formed during volcanic eruptions when the moon still had volcanic activity, over 3 billion years ago, and today new glass is thought to be generated from the intense heat and pressure caused by meteorites colliding with the moon’s surface. If the conditions are intense enough, it may cause the silicon in moon rocks to form a glass like substance, similar to how natural glass and most sand is formed on earth. This is most likely how the depicted spheres were formed, as the intact shapes suggest they were formed more recently. In a recent paper published about the findings, planetary geologist Zhiyong Xiao of Sun Yat-sen University in China said that ‘Glass is ubiquitous in lunar regolith, and volcanism and hypervelocity impacts are the major mechanisms of forming lunar glass’. 


Overall, although the new images may seem widely insignificant as they appear to show only a small feature of the moon, they have a wider impact on our understanding of the history of the moon and what conditions are like. This not the first time lunar glass has been detected, and it will most likely not be the last, but the larger nature of the spheres makes the images more uncommon and suggests that there may be other secrets to the moon that are yet to be discovered, whether that is by Yuta-2 itself, future rover missions or direct human involvement in the future.