Weird 'Gel-like' Substance Found on Moon by China's Lunar Rover Yutu-2

A strange "gel-like" substance has been found on the surface of the moon by China's lunar rover Yutu-2. The material was described as being "unusually colored," and according to the state-run newspaper People's Daily, mission scientists are now trying to work out what it is.

"Yutu-2 rover, part of China's Chang'e-4 mission, has discovered an unusually colored "gel-like" substance during its exploration activities on the far side of the moon," the newspaper tweeted.

The discovery was described in more detail in the Chinese language publication Our Space as part of Yutu-2's "drive diary," Space.com reports. The substance was found on 28 July, during "day 8" of an exploration mission to a region covered in small impact craters.

Scientists working on the Chang-e-4 mission were about to power down the rover for a "nap" when they noticed a crater with a strange material in one of the images sent back from Yutu-2's main camera.

Yu Tianyi, from the the drive team, saw the gel in the inner edge of the impact crater, Our Space notes. He contacted mission scientists who decided to postpone the rover's planned route and examine the crater and the material inside. According to Our Space, the gel's shape and color was "significantly different from the surrounding lunar soil."

There have been no updates since the original announcement of the "mysterious material," but People's Daily said researchers are currently analyzing it. "Mission scientists are now trying to figure out what the mysterious material is," it tweeted. "What do you think it is?"

Mahesh Anand, Vice President of the U.K.'s Royal Astronomical Society and planetary scientist at the Open University, told Newsweek in an email that while there is very little information to go on, the material could be a very fine-grained volcanic glass that is distinct from the surrounding material.

"The fact that it has been observed associated with a small impact crater, this finding could be extremely exciting as it would indicate that a very different material could just be hiding underneath the very top surface," he said. "This would assume even a greater significance if these material turn out to have experienced interaction with water-ice (as the possibility of existence of water-ice in the top few meters of the lunar South polar region is predicted on the basis of recent remote sensing dataset)."

Walter Freeman, a physicist from Syracuse University, New York, also said the substance could be lunar dust that has melted into a glass following a meteorite impact. "We have lots of processes on Earth that cause interesting geology: the action of water, wind, and volcanism. But the Moon has none of these, so meteorite impacts are the main thing that reshapes its surface," he told Newsweek.

"There's a bit of precedent for this on Earth: at the site where the first nuclear bomb was tested in New Mexico, there is a glassy mineral called 'trinitite' formed from the heat of the explosion. The same thing happens around meteorite impacts here."

The Chang-e-4 lander and Yutu-2 rover landed on the far side of the moon in January, becoming the first spacecraft to reach this unexplored region of Earth's only satellite. The chart below, from Statista, shows the history of moon landings over the past 15 years.

"The far side of the moon has unique features never before explored on site," Zou Yongliao, who is in charge of lunar exploration at the Chinese Academy of Sciences, told Xinhua at the time. "The exploration of this virgin land by Chang'e-4 might bring breakthrough findings."

The moon is tidally locked to Earth, meaning we only ever see one side of it. It is thought the geology of the far side is very different to the side that faces us—but until now no probe had ever been there.

Yutu-2 landed in the Aitken Basin, thought to be one of the biggest impact craters in the solar system. It has been analyzing the chemical composition of rock and soil in the crater and measuring surface temperatures—understanding the terrain could help researchers plan future missions to the moon.

This article has been updated to include comments from Mahesh Anand and Walter Freeman.