A Chinese rocket booster slammed into the far side of the Moon last year and left two craters.
American scientists believe that they’ve pinpointed where the booster came from, and show that it was carrying the mystery object that made the second crater.
Without cooperation from the team behind the Chinese mission, the University of Arizona researchers say we may never know what the unknown item was.
When a spent rocket booster slammed into the far side of the Moon in March 2022, it apparently had an unknown object attached to it. Now we know the booster was Chinese in origin.
But to muddle matters, the China National Space Administration (CNSA) say it wasn’t their rocket booster—and therefore couldn’t have been their mystery second item—that left the two craters on the Moon. Data tells a different story.
The story of this mystery starts well before a piece of space junk hurtled into the Moon near the Hertzsprung Crater, a place never directly visible from Earth. It was the two craters created there that really got folks wondering about this space junk.
A research team from the University of Arizona started investigating—their findings were published in Planetary Science Journal—and now say they have “definitive proof” that the space junk was a spent booster from a Chinese rocket. They also claim that it was likely hauling an additional payload, hence the second crater.
If they’re correct, this space junk had spent years in orbit, and had been identified by the Catalina Sky Survey as WEO913A. Thanks to its path, the team soon narrowed down that the object was a rocket booster from either a 2015 SpaceX Falcon 9 launch or the late 2014 Chnge’e 5-T1 launch—the latter of which was carried out by the CNSA’s lunar exploration program. The CNSA claimed that the rocket booster burned up upon re-entry to Earth, but the U.S. Space Command says that never happened.
The third and uppermost stage of the rocket, which was on a dry run for a mission to bring lunar soil back to Earth, was jettisoned once spent. As it was too small to be seen by the highest-powered telescopes, light curve characterization and computer simulations of thousands of objects in space were key in determining the object’s origin. And researchers found something else intriguing in the course of their research.
“Something that’s been in space as long as this is subjected to forces from the Earth’s and the Moon’s gravity and the light from the sun,” Tanner Campbell, doctoral student at the University of Arizona Department of Aerospace and Mechanical Engineering in the College of Engineering and the study’s first author, said in a statement. “So, you would expect it to wobble a little bit, particularly when you consider that the rocket body is a big empty shell with a heavy engine on one side. But this was just tumbling end-over-end, in a very stable way.”
The team realized that there must have been a counterweight to the two engines, each weighing 1,200 pounds without the fuel. After performing a torque balance analysis, the team came to believe that something was mounted to the front of the booster. And the clues from the impact—which made two craters about 100 feet apart, each roughly 50 to 60 feet in diameter—indicate a decently sized mystery object.
“This is the first time we see a double crater,” Campbell said in regards to rocket boosters hitting the Moon. “We know that in the case of Chang’e 5-T1, its impact was almost straight down, and to get those two craters of about the same size, you need two roughly equal masses that are apart from each other.”
In the case of the wayward rocket booster and its unknown friend, definitive answers may never come. “Obviously, we have no idea what it might have been—perhaps some extra support structure, or additional instrumentation, or something else,” Campbell said. “We probably won’t ever know.”
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