The mysterious rocket booster that crashed onto the far side of the Moon on March 4, 2022, has been located by NASA's Lunar Reconnaissance Orbiter (LRO), which serves as the agency's eye in the sky in orbit above the Moon.
Astronomers now have a brand-new puzzle to solve after the LRO photos from May 25th revealed not only a single, but a twin crater created by the rocket's impact.
Why are there two craters? Double craters are uncommon—none of the Apollo S-IVBs that struck the Moon produced any—but they are not inconceivable—especially if an object collides with the Moon at a low angle. However, it doesn't seem to be the situation here.
The booster "came in at roughly 15 degrees from vertical, so that's not the reason for this one," says astronomer Bill Gray, who initially detected the item and foresaw its destruction on the moon back in January.
An 18-meter-wide eastern crater and a 16-meter-wide western crater make up the impact site. The LRO Camera team's principal investigator, Mark Robinson, suggests that an object with different, significant masses at either end might be the cause of this twin crater creation.
"Typically a spent rocket has mass concentrated at the motor end; the rest of the rocket stage mainly consists of an empty fuel tank. Since the origin of the rocket body remains uncertain, the double nature of the crater may help to indicate its identity," he explained.
So what is it?
It's a lengthy tale. Astronomers initially became aware of the unnamed rocket earlier this year when it was revealed to be an upper stage from a SpaceX rocket that had carried NASA's Deep Space Climate Observatory (DSCOVR) to the Sun-Earth L1 Lagrange Point in 2015.
When his software pingged a mistake, Gray, who creates software that tracks space debris, was informed of the item. On January 26, he stated to The Washington Post that "my software complained because it couldn't project the orbit past March 4, and it couldn't do it because the rocket had hit the Moon."
In late January, Gray shared the word and the news traveled widely; nevertheless, a few weeks later, he got an email from Jon Giorgini at the Jet Propulsion Lab (JPL).
Giorgini noted that DSCOVR's trajectory shouldn't have brought the rocket even remotely close to the Moon. Gray dug further into his data to try to explain the divergent trends and found that he had incorrectly recognized the DSCOVR booster back in 2015.
Gray's investigation revealed that it was really the upper stage of China's Chang'e 5-T1 mission, a 2014 technology demonstration mission that prepared the way for Chang'e 5, a 2020 lunar sample return mission that was a success (incidentally, China recently announced it would follow up this sample return mission with a more ambitious Mars sample return project later this decade).
Jonathan McDowell provided some supporting evidence that appeared to support this new idea on the identity of the item. The puzzle was cleared up.
The Chinese Foreign Minister, however, insisted that it was not their rocket because it had deorbited and fallen into the water shortly after launch, days later.
Currently, Gray is still of the opinion that Chang'e 5-T1 was the rocket that collided with the Moon, and he suggests that the Foreign Minister was merely mistaken in thinking Chang'e 5-T1 was the same as Chang'e 5. (whose booster did indeed sink into the ocean).
Regarding the newly discovered twin crater on the Moon, the LRO team's swift discovery of the impact site is a remarkable accomplishment in and of itself. With a little assistance from Gray and JPL, who each individually reduced the search region to a few dozen kilometers, it was found just months after impact.
For instance, it took more than six years of meticulous investigation to locate the Apollo 16 S-IVB crash site.
Here is Bill Gray's opinion on the twin crater impact and his narrative of the booster identification drama. You may find the LRO pictures here.
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