Researchers believe they have finally confirmed the identity of the object that crashed into the moon on March 4, 2022, and explained why space debris left two craters on the moon’s surface instead of one. According to a team of engineers at the University of Arizona, the object is the fuselage of the Long March 3C rocket recovered from China’s Chang’e 5-T1 mission in 2014. This mission was designed to test the subsequent lunar lander.

The most likely cause of the double crater is the additional payload on the rocket, which the China National Space Administration (CNSA) did not disclose. But it would be hard to tell what it is without close examination: The craters are on the far side of the Moon and can never be seen directly from Earth.

“This is the first time we’ve seen a double crater,” says Tanner Campbell, an aerospace engineer at the University of Arizona.

“We know that in the case of Chang’e 5 T1, the impact was almost straight down, and you would need two bodies approximately equally spaced apart to get these two craters that are roughly the same size.”

The astronomer tracked the object, named WE0913A, from its discovery by the Catalina Sky Survey in March 2015 until its final encounter with the lunar surface last year. It was initially thought to be a Space X launch vehicle, but suspicions soon fell on a 2014 mission to China.

In this latest study, the team analyzed the movement of the unidentified object and the changes in reflected light just before impact to determine exactly what happened. The object’s rotation in space (tipping end-over-end) implied a second mass acting as a counterweight to the engines on one side of the rocket, which explains the double crater. CSNA did not say what the extra burden was and denies it was theirs.

“Obviously we have no idea what that might be; maybe it’s some kind of extra support structure, extra hardware, or something else,” Campbell says.

“I guess we’ll never know.”

It’s not uncommon for spacecraft to launch rockets into space, or even for those rockets to crash into the moon, but this latest incident is a reminder that space debris is a growing problem. It has the potential to cause serious damage to orbiting satellites and the International Space Station; however, most of the debris will burn up in the atmosphere before reaching Earth. Researchers of this latest study say anything that goes into space should be carefully monitored.

“As we put more and more objects on the Moon, it becomes extremely important that we not only track the object, but also understand what they will do once they get there,” says Roberto Furfaro, a mechanical engineer at the university. He’s from Arizona.