SpaceX booster expected to unintentionally hit the moon on March 4

An expert in software tracking objects in space says that a SpaceX rocket booster is "certain" to impact the moon in a few weeks, marking what is believed to be the first case of unintentional space junk hitting the Earth's moon.

Bill Gray has been tracking the Falcon 9 upper stage as part of his Project Pluto blog. The rocket booster was originally launched from Florida in February 2015 in order to send up a space weather satellite, marking the first SpaceX launch into interplanetary space.

Since then, the booster has run out of fuel and is unable to return to Earth or to get out of the gravity of the Earth-Moon system, according to meteorologist Eric Berger, who wrote about the Falcon 9's upper stage in a recent post for Ars Technica. Since then, Berger says the booster has been following a "chaotic orbit" in space.

But Gray, using his software and other available data, wrote in his Jan. 21 blog post that he predicts the booster will hit the far side of the moon on March 4. The four-ton booster is calculated to make impact at 2.58 km/second.

His calculations, as well as his prediction of March 4 as the date of impact, were confirmed in a tweet by Jonathan McDowell, an astronomer from the Harvard Smithsonian Center for Astrophysics.

There are some small uncertainties that could impact the orbit of the booster, including light from the sun "pushing" the object and altering its course minutely. These changes may impact exactly where the booster lands, which Gray is continuing to track and predict, but he says he is "100 per cent certain" that it will make an impact somewhere on the moon.

When it comes to whether people should be worried about the impact, Gray says there is "zero concern," adding that the moon is hit with larger natural space objects like asteroids at even faster speeds "fairly routinely." But when it comes to man-made objects and space junk, Gray says this is the first unintentional case of impact of which he is aware.

While this event will likely be unobservable from Earth, Gray says there is a possibility that there could be something to learn about the moon because of this impact.

NASA's Lunar Reconnaissance Orbiter and India's Chandrayaan-2 are expected to eventually pass over the site of the booster's hit. If the exact location on the moon can be determined, Gray says the lunar orbiters could "see a very fresh impact crater" and possible "ejecta" -- material expelled from under the surface of the moon from the force of the impact.

From these observations, researchers could learn more about the geological makeup of the moon.

"I am rooting for a lunar impact," Gray wrote.