Probable crash site of mysterious space junk spotted on the far side of the Moon

Probable crash site of mysterious space junk spotted on the far side of the Moon

The newly formed twin crater, spotted on the far side of the Moon near Hertzsprung crater.

The newly formed twin crater, spotted on the far side of the Moon near Hertzsprung crater.
Image: NASA/Goddard/Arizona State University

Observations made by NASA’s Lunar Reconnaissance Orbiter have allowed scientists to pinpoint the location where a mysterious object – likely an abandoned rocket body – crashed into the Moon several months ago.

The crash site is located near the Hertzsprung crater on the far side of the Moon, exactly where astronomers thought it might be. Before and after images collected by the Lunar Reconnaissance Orbiter (LRO) allowed scientists to spot two newly formed craters generated by the impact, which happened on March 4, according to a NASA Press release. That two craters formed from a single apparent object is now a question that needs answering.

The before-after images show the sudden appearance of the double crater.
GIF: NASA/Goddard/Arizona State University

Confusion still exists as to the origin of the abandoned piece of space junk. It was originally thought to be the upper stage of an abandoned Falcon 9 rocket that SpaceX launched in 2015, but further analysis pointed at a remnant of China’s Chang’e 5-T1 lunar mission from 2014. The problem is that the Chinese authorities have categorically denied that the object belongs to them. Speaking to Inside Outer Space in February, Bill Gray, creator of Project Pluto, software for scanning solar system objects, said“There really is no good reason at this point to think the object is anything other than the Chang’e 5-T1 booster” and anyone “claiming otherwise has a pretty big mountain of evidence to overcome.”

Either way, it appears to be the first time a piece of space junk has inadvertently crashed into the lunar surface. Our stuff has crashed on the Moon before, but these incidents were intentional or failed attempts at lunar landings.

Prior to impact, NASA said LRO would not be able to observe the impact, but the orbiter would be able to monitor environmental changes consistent with a crash site. NASA said the process could take weeks or even months, which turned out to be the case, as the impact happened about four months ago.

In an email, Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, said the crash site is “moderately close to the intended point of impact.” For you, lunar cartographers, the intended place was 233.55E 5.18N, while the actual location turned out to be 234.49E 5.23N. “Newton wins again,” McDowell joked.

The impact unexpectedly formed two craters: an eastern crater measuring 59 feet (18 meters) wide and a partially capped western crater measuring 52.5 feet (16 meters) in diameter. The greatest combined width of the crater is 92 feet (28 meters). As for the cause of the double crater, here’s what NASA had to say:

The double crater was unexpected and may indicate that the rocket body had large masses at each end. Typically, a spent rocket has mass concentrated at the engine end; the rest of the rocket stage consists mostly of an empty fuel tank. Since the origin of the rocket body remains uncertain, the dual nature of the crater may help point to its identity.

McDowell disagreed with that assessment, writing in his email that he “could just have come at an unusual angle with a bounce”, but he was clear to emphasize, “I’m not an expert. in craters.”

Interestingly, this is the first documented case of an artificial object forming a double crater (double craters are a common montage of asteroid impacts, as they often travel – and subsequently crash – in pairs). During the Apollo missions, the third stage of Saturn V rockets and the second stage of Saturn IB launch vehicles (collectively known as S-IVBs) were deliberately crashed into the Moon, forming oddly shaped craters. Curiously formed, but no double craters.

Four examples of craters formed by Apollo rocket bodies - none featuring the double crater.

Four examples of craters formed by Apollo rocket bodies – none featuring the double crater.
Image: NASA/Goddard/Arizona State University

NASA’s explanation for the double crater sounds plausible, but I’m not entirely convinced. These craters could actually be the result of two meteors hitting the Moon’s surface, although I’ll admit the odds of this happening at virtually the same time and place as the mystery object’s projected impact seem highly implausible. Hopefully scientists will soon identify the source of the space junk so we can finally put an end to this story.

Correction: An earlier version of this post listed one incorrect predicted impact location.

After: NASA declares Megarocket rehearsal complete, setting the stage for maiden launch.

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