You know you’re living in the space age when a rocket hits the moon and the industry as a whole is pointing up at the sky and like an angry teacher holding up a paper airplane asking, “Who started that?!” That’s exactly what happened this one Week when an unidentified rocket stage (!) hit the lunar surface, forming a new and interesting crater and left us all wondering how it’s possible not to know what happened.
The short version of this story is that skywatchers led by Bill Gray spent months tracking an object that they calculated would soon hit the moon. It was obviously a piece of rocket junk (rockets produce a ton of junk), but no one stepped up to say, “Yes, that’s ours, sorry.”
Based on their observations and discussions, these amateur object trackers (though by no means lacking in expertise) determined that it was most likely a 2015 SpaceX launch. But SpaceX didn’t conform, and after a while Gray and others, including NASA, decided it would be more of a 2014 launch from China. China denied this, saying the launch vehicle in question burned up on reentry.
Maybe they’re telling the truth; Maybe they don’t want to be responsible for the first completely accidental moon impact in history. Other spacecraft have hit the moon, but it was intentional or part of a botched landing (in other words, the impact was intentional, just a little harder than expected) — not just a wayward piece of space junk.
Maybe we’ll never know, and that’s really the strangest thing of all. With hundreds of terrestrial telescopes and radars, space-based sensor networks and cameras pointing in all directions – and that’s just the space surveillance we know! – It seems amazing that an entire rocket stage managed to stay in orbit for six or seven years and finally made it all the way to the moon without being identified.
Animation by Tony Dunn showing the mysterious object (green) orbiting and eventually impacting the originally estimated March date. Photo credit: Tony Dunn
I thought someone at LeoLabs, who have been building a new network of debris-detecting radars around the world, might have a little insight. Darren McKnight, senior technical fellow there, had the following answers to my questions.
How is it possible that we didn’t know the identity and trajectory of such a large and relatively recently launched object?
Tracking decaying objects in Cislunar’s orbit is unlikely to be a high priority for government sensors when they can spend that time observing satellites or space junk that are closer to Earth. However, tracking and monitoring operational satellites in cislunar orbit is indeed critical for strategic intelligence given the new high-altitude terrain involved.
Would such confusion be possible with an object launched now?
Yes, that could happen again now that the technology used by the US government to track space objects hasn’t changed in many years.
Will there likely be more of these “mysterious objects” making an impact here and there in the years to come?
It’s possible that an accidental lunar impact like this could happen again in the future, depending on the number of missions placing rocket bodies in those orbits and given enough time (years or decades). But events like this should generally remain extremely rare.
And as Bill Gray states in his article:
…High-altitude debris was of no concern to anyone outside of asteroid exploration, and even we didn’t care too much about it. Objects of this type are not tracked by the US Space Force; They use (mostly) radar, which is “short-sighted”: It can track objects as small as 10 cm in diameter in low orbits, but can’t see large rocket stages like this one when they’re as far away as the moon. You need telescopes for that.
Strange as it may seem (at least to me), orbits for objects of this type are only calculated by me in my spare time.
It’s remarkable in a way, but as anyone in the space surveillance world will tell you, there’s a lot to see up there and you have to choose your targets. It’s not easy or simple to get a good picture of a rocket-sized object halfway to the moon.
Our best clue to the object’s identity may actually be the crater it left behind when it hit. The impact site was imaged shortly thereafter and has an odd double-O shape: two overlapping craters, one 18 meters wide and the other 16 meters. Here’s the before and after:
“The double crater was unexpected and could indicate that the rocket body had large masses at each end. Typically, a spent rocket has mass concentrated at the motor end; the rest of the rocket stage consists mostly of an empty fuel tank,” wrote NASA’s Mark Robinson.
In truth, while it’s an enticing mystery, there doesn’t seem to be any reason to devote serious resources to finding out. Stranger things happen in space than a piece of a rocket taking off at the exact angle and speed needed to eventually hit the moon. And for all we know, someone out there knows what this weird, double-sided piece of space junk is, but would rather keep it a secret.