A Falcon 9 rocket kicked into the moon on March 4. The rocket stages normally have to return to Earth, but this particular stage didn’t have enough fuel to return, so it floated through space for nearly seven years.
At the February 2015 launch of the Deep Space Climate Observatory, a weather surveying satellite a million kilometers away, the Falcon 9’s second rocket stage should have returned to Earth to burn up in the atmosphere. The stage had fallen so far from Earth after launch that there was not enough fuel to return it. However, there was also not enough fuel to outrun the gravitational forces of the Moon and Earth, causing the stairs to follow a “chaotic” path through space.
But that will come to an end on March 4, Bill Gray, creator of the Project Pluto software, told Ars Technica. Based on data from amateur and professional astronomers, he says the second stage of the Falcon 9 rocket will then crash into the moon. Where exactly is unclear, because the forces that sunlight exerts on the debris are difficult to calculate, but it is likely to crash on the far side of the moon.
The rocket stage weighs about four tons and is expected to crash at 2.58 kilometers per second. It is known for the first time that space junk accidentally crashes on the moon. That’s noticeable, but nothing to worry about says Jonathan McDowell, astronomer at the Center for Astrophysics, a Harvard and Smithsonian institution. “Just an extra hole in the green cheese”, he writes on Twitter† Whether researchers can learn anything from the collision is unclear. That depends, among other things, on whether it plops on the visible or invisible side of the moon, Gray says.