For the first time, a piece of space debris inadvertently crashed onto the moon. On March 4, at 11.25:58 a.m. Dutch time, about a few seconds later, an object hit the moon at 2.58 kilometers per second (9,300 kilometers per hour). This object is likely the last rocket stage of the Chinese Chang’e 5-T1 lunar mission. The impact point is located on the edge of the lunar crater Hertsprung, not far from the equator on the far side of the Moon. As a result, the effect is not visible from the ground.
The effect was announced in January by astronomer Bill Gray, who has been hunting asteroids for years using proprietary software and telescope observations by amateur and professional astronomers. The neglected missile stages are an accidental catch of this one, recognizable by their distinct brightness differences as they tumble in sunlight.
Gray’s announcement immediately caused an uproar, especially since he initially thought it was the second stage of the SpaceX Falcon 9 rocket, which launched NASA’s DSCOVR space probe in 2015. SpaceX, Elon Musk’s space company, has long been the center of attention, Because of the growing problem of space debris, the accidental collision is indifferent to say the least.
But then Gray received an email from an engineer involved in the DSCOVR mission. The gray object and other astronomers who discovered it in 2015 cannot be a Falcon 9 trap because it is in a completely different orbit. Gray had to go back to his notes on the original classification in 2015, then found a better candidate: the Chinese Chang’e 5-T1 moon mission that launched in October 2014.
The identification was confirmed by doctoral students from the University of Arizona, who analyzed the color spectrum of the rocket stage. Chinese colors match better than SpaceX’s. China’s space agency CNSA has not yet commented on identification.
The effect in itself is nothing special: the moon hits more often, including heavier and faster chunks of space rock, hence its wormhole appearance. In 2009, NASA ordered a Centaur rocket stage to hit the moon on the LCROSS mission, in order to analyze rocket launchers.
The expected effect even provides a “free” replay of this observation: Two orbiting satellites, NASA’s Lunar Reconnaissance Orbiter and India’s Chandrayaan-2, can take pictures of the new crater afterward (the chance of an impact). Being able to see it live is minimal.)
The fact that only a useful asteroid fighter saw the incoming impact worries explorer Bill Gray. Objects in low Earth orbit, including thousands of satellites and tens of thousands of pieces of space debris, are closely monitored from Earth to predict collisions. “But I am (to my knowledge) the only person on our green planet that calculates orbits and predicts space debris in very high orbits,” Gray writes on his website†
Since more and more spaceflights are also taking place in these higher orbits, and both NASA and China have announced manned flights to the Moon, it is also wise to observe this space debris in a more structural way.
A version of this article also appeared on NRC on the morning of February 22, 2022