Whenin a crater on the far side of the moon last year, there was an understandable sense of excitement. What was it? Aliens? Space snot? Melted rock?
A team led by researchers at the Chinese Academy of Sciences published an analysis of the substance in the journal Earth and Planetary Science Letters.
It's rock, more specifically "impact melt breccia." Breccia is rock made up of fragments of rocks or minerals cemented together, like a geologic version of one of those Jell-O salads packed with fruit bits. Melt it down and it can become glassy-looking.
Yutu-2, part ofto investigate the mysterious far side of the moon, . The maneuver gave scientists lots of data to work with to come to the melted-rock conclusion.
The researchers described the substance as "dark greenish and glistening" and measured it at about 20 inches (52 centimeters) wide. "It was formed by impact-generated welding, cementing and agglutinating of lunar regolith and breccia," the team reported.
A meteorite impact is a likely suspect. "Glasses in the lunar regolith are usually sourced from impact melts or from volcanic eruptions," the study said.
The study also found the melted rock resembles lunar impact melt breccia samples returned by NASA's Apollo moon missions.
One of the big questions around the "gel like" substance appears to have been answered. It wasn't aliens, but it was a fun moon mystery with a satisfying conclusion.