A mysterious crash on the moon’s surface last year left scientists wondering what created a pair of craters. A new analysis from the University of Arizona found that the crash involved remnants of a Chinese rocket booster.

The Chinese rocket was hauling an unknown payload that created a second crater when it crashed into the moon.

American scientists say it was a booster that came off a Chinese rocket that went tumbling slowly toward the moon. They found the booster created one crater, and a second crater was formed by a mysterious object attached to the booster.

China is challenging the findings of the U.S. research team and refutes the claim that Chinese spacecraft caused the craters.