Although the rocket's origin hasn't been confirmed, a Chinese rocket booster remains the prime candidate.

In January, amateur astronomers and astronomical software writer Bill Gray found evidence that a disused rocket booster was on a collision course with the Moon. At first this was thought to be a SpaceX Falcon 9 second stage rocket used to launch the Deep Space Climate Observatory (DSCOVR) probe in 2015, but additional data and calculations later determined that the most likely candidate was the upper stage of a Chinese Long March 3C used to launch the Chang'e 5-T1 lunar flyby mission in 2014.

Because the impact of the Chinese rocket was predicted to take place in the dark on the far side of the Moon, the event couldn't be seen from the Earth, so matters rested there. However, the LRO was in a position to take images of the crash site afterward and send back evidence to confirm the impact near Hertzsprung crater in the Mare Orientale region.

The surprising result was the discovery of not one, but two impact craters at the site. Until now, rocket impacts on the Moon, such as those left by the Apollo mission S-IVB boosters, have been single craters with an irregular outline.