A SpaceX rocket that has been drifting in space for a year and a half is set to crash into the moon on Wednesday, stirring up a debris cloud that could be visible from Earth. The impact raises questions on the future of lunar exploration, including how to protect any future moon bases from space junk.
The rocket set for moon impact is the upper stage of a Falcon 9 that transported a pair of lunar landers. While the landers successfully reached the surface, the rocket was left adrift since it did not have enough fuel to return to Earth or enter a stable orbit.
Weighing 4 metric tons, the rocket is expected to strike the lunar surface at a speed of approximately 5,400 mph—about seven times the speed of sound. Without an atmosphere to slow the projectile down, the impact will cause an explosion equivalent to 3 metric tons of TNT, leaving a crater that’s projected to be up to 27 meters in diameter and 5 meters deep.
The upper stage is expected to hit the surface around 6:34 am UTC on Wednesday, likely making impact near Einstein Crater on the western edge of the moon’s near side. The Americas will have the best view of this impact. While it won’t be visible to the naked eye, viewers should be able to spot the debris plume through a good telescope for a few minutes.
A lunar crash landing visible from Earth will be a spectacle, one that raises concerns about the future of the moon. Multiple countries are planning uncrewed lunar missions, which could clutter the area around the moon. This SpaceX rocket won’t be the first to accidentally crash into the moon. In March 2022, a Chinese Long March 3C rocket also struck the lunar surface and left a crater that’s 29 meters wide.
China and the US are also pushing to build bases on the surface in the coming decades.
Bill Gray, the creator of the Project Pluto initiative to develop software and tools to track the orbits of asteroids, comets, and artificial satellites, was the first to calculate the trajectory of the impending Falcon 9 crash. He was also part of a team that worked on a preprint study released last month detailing the collision.
The crash landing is ”an opportunity to test pipelines for measuring flash properties to locate impact events seismically, and to better understand the multi-modal hazards posed to future lunar infrastructure and astronauts from space debris impacting the Moon,” the study states.
Although building a moon research center capable of supporting a sustained human presence will take at least a decade, NASA’s missions to construct the first facilities are expected to launch in the coming years as part of the Artemis program.
“These sorts of things are going to happen more and more often. And as we have more astronauts on the lunar surface, more lunar infrastructure habitats, for example, we need to understand how much of a risk these impact events actually pose,” Benjamin Fernando, a researcher at Los Alamos National Laboratory in New Mexico and coauthor of the preprint study, tells ABC News.
The risk posed by space debris is part of a growing list of hazards that cast doubt on the safety of any long-term project on the moon. In addition to the potential for space junk to wreak havoc on the lunar surface, natural events such as meteorite strikes also threaten any future activities. But with any potential lunar bases still a decade or more away, there’s ample time for researchers to look at the hazards and plan for them.
“This is an ideal way of studying both the direct risks, the risk of being hit by debris or being blinded by a flash of light, but also the indirect risk, the risk of being hit by a cloud of ejected material and having that disrupt or interfere with spacecraft functions in lunar orbit as well,” Fernando says.