Yutu-2 rover, a part of China's Chang'e 4 lunar lander mission discovered a peculiar gel-like substance in a small impact crater on the far side of the Moon in 2019. First, the substance looked like gel but later it looked like a glossy substance. A team led by scientists at the Chinese Academy of Sciences published an analysis of the substance in the journal Earth and Planetary Science Letters. According to the analysis, the substance has been identified as 'Rock' and is more specifically an impact melt breccia - fragments of rocks or minerals cemented together.

The scientists explained in their paper that "Chang'e-4 rover spotted a dark greenish and glistening impact melt breccia in a crater during its traverse on the floor of Von Karman crater within the South Pole Aitken (SPA) basin on the far side of the moon. It was formed by impact-generated welding, cementing, and agglutinating of lunar regolith and breccia.

The pictures captured using Yutu-2's Panoramic Camera, Visible and Near-Infrared Imaging Spectrometer (VNIS), and hazard avoidance camera support this study. The term regolith is used to refer to a layer of unconsolidated solid material that covers the base of the planet. The structure is suspected to have been formed following a meteorite impact at the location. Regolith is made up of plagioclase (around 45 percent), pyroxene (7 percent) and olivine (6 percent).

The substance found is very similar to the samples 'Lunar Sample 15466 and Lunar Sample 70019' that were returned to Earth by NASA's Apollo missions. Chang'e 4 is a first robotic spacecraft mission, part of the second phase of the Chinese Lunar Exploration Program. It achieved the first soft landing on the far side of the Moon took place on 3 January 2019.