Mystery Rocket That Crashed Into the Moon Left a Double Crater

UPDATE 6/27: The rocket which hit the moon back in March still remains a mystery, but NASA has now discovered the point of impact and an unexpected double crater as you can see in the image above.

As NASA explains, typically a spent rocket only has mass concentrated at one end. To create a double crater like this suggests mass at both ends. In this case, one crater (eastern) is 18 meters in diameter, where as the other (western) is 16 meters in diameter.

No other rocket impact with the moon has created a double crater, but that's potentially good news. The unusual impact may ultimately help identify exactly which rocket it is, but for now it still remains a mystery.

UPDATE 2/14: Last month, we all thought that part of a SpaceX Falcon 9 rocket was set to hit the moon on March 4. However, it turns out astronomers were wrong in identifying the rocket. It's not a Falcon 9 after all.

Bill Gray, who writes the Project Pluto software, originally identified the rocket as the Falcon 9 used to launch the NOAA Deep Space Climate Observatory mission (DSCOVR) back in 2015. The launch occurred two days before the object known as WE0913A passed the moon, and as Gray explains, "the object had about the brightness we would expect, and had showed up at the expected time and moving in a reasonable orbit."

There was no conclusive evidence, but enough "good circumstantial evidence" to flag WE0913A as part of a Falcon 9 rocket. However, Gray was wrong. As Ars Technica reports, NASA Jet Propulsion Laboratory engineer Jon Giorgini got in touch with Gray on Feb. 12 to point out the trajectory of the object didn't fit with the DSCOVR spacecraft's trajectory. WE0913A was in "another part of the sky" with a "suspiciously large separation" to the spacecraft.

Giorgini's observations prompted Gray to revisit the archives and look at earlier space missions. Based on the new evidence he gathered, combined with orbital elements for a cubesat provided by astrophysicist Jonathan McDowell, Gray is now sure WE0913A is the booster from China's Chang'e 5-T1 mission, which launched in October 2014.

So an object is still set to hit the moon on March 4, but it's a booster made by the China Academy of Space Technology (CAST), not, as we previously thought, a SpaceX Falcon 9 rocket stage.

Original Story 1/26:
Part of a SpaceX Falcon 9 rocket weighing 4 metric tons is expected to crash into the surface of the Moon on March 4.

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As Ars Technica reports, the Falcon 9 second stage has been following a chaotic orbit for the past seven years after it failed to escape the Earth-Moon system gravity following a 2015 launch. It formed part of a SpaceX rocket used to lift the NOAA's Deep Space Climate Observatory (DSCOVR) into orbit, and you'd be forgiven for forgetting it was up there, tumbling out of control.

Recent observations by Bill Gray, who writes the Project Pluto software used to track near-Earth objects, predict the rocket section will hit the surface of the Moon on March 4. However, there are still nearly six weeks until that happens, and a number of factors could alter its path, albeit slightly. Gray is asking astronomers around the world to keep an eye on the object in the coming weeks to help refine the prediction.

For now, it's expected to hit the far side of the Moon near the equator on March 4. NASA will be keen to know exactly when and where the rocket stage will impact so it can position satellites to observe the subsurface material the heavy object throws up.