Scientists are scratching their heads after China’s lunar rover Yutu-2 discovered an unknown, gel-like substance on the surface of the moon.
The discovery was made on July 28 during “lunar day 8” of an exploration mission to a region on the far side of the moon, NBC News reports. Day 8 began on July 25 and ended on July 28, according to a Yutu-2 “drive diary” published on Aug. 17 by the Chinese-language publication Our Space.
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 substance depicted on Yutu-2’s main camera. Excited by the discovery, Space.com reports that the rover’s drive team called in their mission scientists and together decided to postpone Yutu-2’s plans to travel west and instead proceeded to more closely examine the material.
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According to Our Space, the gel was “significantly different from the surrounding lunar soil” in shape and colour. Since the original announcement, there have been no updates on the substance, but the Chinese publication People’s Daily reports that scientists are currently analyzing it.
While the substance has piqued the interest of the scientific community, few have any idea what the substance could be. Mahesh Anand, vice president of the U.K.’s Royal Astronomical Society, told Newsweek in an email that the gel substance could be a fine-grained volcanic glass.
“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 wrote in the email.
“This would assume even a greater significance if these materials turn out to have experienced interaction with water-ice (as the possibility of existence of water-ice in the top few metres of the lunar South polar region is predicted on the basis of recent remote sensing data set).”
China made history earlier this year when it successfully landed the Chang’e lander and rover on the far side of the moon. The lander and rover docked in the Von Karman crater within the South Pole-Aitken Basin in January 2019.
This part of the moon is not visible to Earth due to a phenomenon known as “tidal locking,” which occurs because it takes 28 days for the moon to orbit the Earth and 28 days to spin once on its axis. This means that the same side of the moon is always facing the Earth.
It’s not possible to shoot signals to the far side of the moon because of this phenomenon, but to resolve this problem, China also built the Queqiao satellite to provide a contact point for the Chang’e-4. In January, Queqiao sent back to Earth photos of the Yutu-2 rover leaving humankind’s first “footprints” on the far side of the moon.
A comparable discovery, NBC News reports, is an orange-coloured substance discovered in 1972 by Apollo 17 astronaut and geologist Harrison Schmitt. It was eventually determined that the soil was created during a volcanic eruption 3.64 billion years ago.