Researchers decode why space junk that crashed onto the moon left not one but two craters

A team of researchers at the University of Arizona's Space4 Center tracked down a defunct piece of a space rocket that crashed onto the moon's surface near the Hertzsprung crater in March 2022 to find out why it left not just one but two craters (about 100 feet apart).

The team, led by Tanner Campbell, a doctoral student at the University of Arizona's Department of Aerospace and Mechanical Engineering in the College of Engineering, has found definitive proof that the object was a booster from a Chinese space rocket that had spent several years tumbling through space and that the abandoned rocket stage likely carried an undisclosed, additional payload.

Seven years ago, an object, designated WE0913A by researchers at the UArizona-led Catalina Sky Survey, was spotted moving at a brisk pace between Earth and the moon. It was initially thought to be an errant SpaceX Falcon 9 rocket booster from a 2015 launch. However, spectral analysis of the object made it more likely to be a booster from a Chang'e 5-T1, a rocket launched in 2014 as part of the Chinese space agency's lunar exploration program.

The Catalina Sky Survey later identified the third and uppermost stage of the Chinese rocket as object WE0913A.

By comparing the light curve data with computer simulations of thousands of hypothetical objects floating through space, the team was able to determine that WE0913A was not what would be expected from a rocket booster.

Further clues from the impact revealed that the rocket booster slammed into the moon, it made two craters, about 100 feet apart, instead of one. Again, very unusual, according to Campbell, who pointed out that the craters left behind by Apollo rockets are either round, if the impactor came straight down, or oblong, if it came in at a shallow angle.

"This is the first time we see a double crater. We know that in the case of Chang'e 5 T1, its impact was almost straight down, and to get those two craters of about the same size, you need two roughly equal masses that are apart from each other," Campbell said.

As for the Chang'e 5 T1 rocket's extra payload, there is a good chance that its identity will remain mysterious, he added.