The Lunar Reconnaissance Orbiter (LRO) – NASA’s eye in the sky in orbit the moon – has found the crash site of the mysterious rocket booster that slammed into the far side of the moon on March 4, 2022.
The LRO images, taken on May 25, revealed not just a single crater, but a double crater formed by the rocket’s impact, helping astronomers unravel a new mystery.
Why a double crater? Although somewhat unusual – none of the Apollo S-IVBs hitting the moon created double craters – they’re not impossible to make, especially if an object hits at a low angle. But that doesn’t seem to be the case here.
Astronomer Bill Gray, who first discovered the object and predicted the moon’s setting in January, explains that the booster “came in at about 15 degrees from vertical. So that doesn’t explain this one.”
The impact site consists of an 18 m wide eastern crater on top of a 16 m wide western crater. Mark Robinson, principal investigator of the LRO Camera team, proposes that this double crater formation could be the result of an object with different, large masses at each end.
“Normally, a spent rocket has mass concentrated at the motor end; the rest of the rocket stage consists mainly of an empty fuel tank. As the origin of the rocket body remains uncertain, the dual nature of the crater may help indicate its identity , ” he said†
So what is it?
It’s a long story. The unidentified rocket first came to astronomers’ attention earlier this year when it was identified as a SpaceX upper stage, launched by NASA’s Deep Space Climate Observatory (DSCOVR) to Sun-Earth L1 Lagrange Point in 2015.
Gray, who designs software that detects space debris, was alerted to the object when his software pinged an error. He told The Washington Post on January 26 that “my software complained because it couldn’t project the orbit after March 4, and it couldn’t because the rocket hit the moon.”
Gray spread the word, and the story was doing the rounds in late January — but a few weeks later, he received an email from Jon Giorgini of the Jet Propulsion Lab (JPL).
Giorgini pointed out that the trajectory of the DSCOVR should not have brought the booster anywhere near the moon. In an effort to reconcile the conflicting trajectories, Gray began digging back into his data, where he discovered that he had misidentified the DSCOVR booster way back in 2015.
SpaceX wasn’t the culprit after all† But there was definitely still an object hurtling toward the moon. So what was it?
A little sleuthing led Gray to determine that it was actually the top stage of China’s Chang’e 5-T1 mission, a 2014 technology demonstration mission that laid the groundwork for Chang’e 5, which successfully returned a lunar sample to Earth in 2020 (incidentally, China recently announced that it would follow up this sample return mission with a more ambitious one) Mars monster return project later this decade).
Jonathan McDowell offered some corroborating evidence that seemed to support this new theory for the object’s identity.
The mystery was solved.
But days later, China’s foreign minister claimed it wasn’t their driver: it had disappeared from orbit and crashed into the ocean shortly after launch.
As it stands, Gray remains convinced it was the Change 5-T1 booster that hit the moon, suggesting that the Secretary of State made an honest mistake by confusing Chang’e 5-T1 with its namesake. Chang’e 5 (whose booster did indeed sink in the ocean).
As for the new double crater on the moon, the fact that the LRO team was able to locate the impact site so quickly is an impressive achievement in itself. It was discovered just months after the impact, with a little help from Gray and JPL, who each independently narrowed the search area to several tens of kilometers.
By comparison, the Apollo 16 S-IVB impact site took more than six years of careful searching to find.
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