Odd gel-like green substance on far side of Moon most likely a rock that melted after meteorite impact: Study
Scientists seem to have deciphered one of Moon's recent secrets. In 2019, the Chinese Chang’e-4 lunar lander made an interesting discovery. It found a sparkling green, gel-like substance, which was unusual, given that the lunar body is known for its dry and dusty landscape.
Now, scientists have unveiled the identity of the strange object. It is Breccia -- a type of rock made of broken pieces of minerals or rock cemented together by finer particles. It is about 52 cm long and 16 cm wide. They speculate that a meteorite impact produced heat to transform a rock into a gel-like substance.
In January 2019, China's Chang’e-4 rover landed on the far side of the moon -- the only robotic mission to have successfully made it to this unexplored region. Data has shown that this part of the lunar body could host water ice, which is a valuable resource that could help future explorers.
"Chang’e-4 rover discovered a dark greenish and glistening impact melt breccia in a crater during its traverse on the floor of Von Kármán crater within the South Pole Aitken (SPA) basin on the lunar farside," the researchers wrote in their study.
On July 28, a member of the team spotted a colored object glowing from a small impact crater. "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. Mission scientists are now trying to figure out what the mysterious material is. What do you think it is?", China's People's Daily, tweeted.
Soon, the rover put its payloads -- Visible and Near-Infrared Imaging Spectrometer (VNIS), and hazard avoidance camera -- to use. Together, these instruments captured detailed images. Their analysis of the images showed that the heat generated from meteorite impact melted a rock, leading to the formation of the glowy gel-like substance.
"Hence, the impact melt breccia was not likely formed in situ in the crater where it was found, but was very likely emplaced in a different event and was ejected to the 2-meter fresh crater," the researchers wrote in their study. The team also identified the composition of the gel-like substance, thanks to the VNIS. It studied the light bouncing off the mystery object. They then compared this with surrounding with the surrounding regolith, which is dust, broken rocks, and other related materials found on the lunar body's surface. The glowy substance was quite similar to other Moon minerals: it contained 38% plagioclase, while the remaining was made of a dark component.
Earlier, other scientists suspected that the gel-substance was not too different from its surrounding. Dan Moriarty, NASA Postdoctoral Program fellow at the Goddard Space Flight Center in Greenbelt, Maryland, told Space.com, "The shape of the fragments appears fairly similar to other materials in the area. What this tells us is that this material has a similar history as the surrounding material. It was broken up and fractured by impacts on the lunar surface, just like the surrounding soil."
The study is published in the Earth and Planetary Science Letters.