Weird Green Gel-like Substance China Found on Moon Identified by Scientists

A strange, gel-like substance found on the surface of the moon by China's Yutu-2 rover has been identified by scientists.

The substance, which was a dark greenish color and glistened, was discovered on the far side of the moon in July last year.

It was first noticed by Yu Tianyi, who works on the drive team. He saw it at the edge of the impact crater and contacted mission scientists, who then decided to reroute the rover to investigate further. According to Chinese language publication Our Space, the substance was very different from the surrounding soil.

"Mission scientists are now trying to figure out what the mysterious material is," the state run newspaper People's Daily tweeted at the time.

Researchers have now published their analysis of the substance in the journal Earth and Planetary Science Letters.

In the study, the team, led by Sheng Gou of the Chinese Academy of Sciences, Beijing, say the gel was found in the Von Kármán crater. This is a large lunar impact crater in the southern hemisphere on the moon's farside. It is part of a much larger impact crater called the South Pole Aitken (SPA) basin, which is around 1,600 miles wide and eight miles deep.

The gel sample was a patch measuring 20 inches by 6 inches and resemble impact melt breccia, a type of rock that forms through an impact event, samples returned from the Apollo missions.

"The dark greenish and shiny features observed from Pancam color image are signs of possible presence of glasses," they wrote. "Glasses in the lunar regolith are usually sourced from impact melts or from volcanic eruptions." As volcanic activity in the region stopped over three billion years ago, the researchers said that is unlikely to be the source.

Instead, they say the gel likely formed as a result of an impact, made up of a mix of minerals. The main component was plagioclase, which is a major constituent in both Earth and the moon's crust. It also contained iron-magnesium silicate minerals olivine and pyroxene.

The team says the gel was a mix of multiple sources, including ejecta from the Finsen crater, located to the northeast of the Von Kármán crater. It also potentially contains material from the Alder crater, to the northwest.

They said the size of the sample is larger than expected. This may suggest the gel did not form where it was found, but was "emplaced in a different event and was ejected" into the crater.

Yutu-2, part of the Chang'e-4 mission, landed on the far side of the moon in 2019. In December last year it set the record for the longest working rover on the moon.

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Yutu-2 on the farside of the moon. Scientists with the Chang'e4 mission have identified the strange gel-like substance found on the lunar surface last year. AFP via Getty Images