On March 4, a defunct SpaceX Falcon 9 rocket will crash into a new impact crater on the moon, which isn't something that happens often, but it will on March 4.

In 2015, NASA's Deep Space Climate Observatory (DSCOVR) mission was launched into space, 1.5 million kilometers away from Earth and towards the sun. The rocket's top stage, however, was too slow to escape into a separate orbit around the sun, thus it was abandoned without a way to return to Earth's atmosphere. Allowing stages to burn up on reentry would be common practice, minimizing the congestion created by harmful trash in near-Earth space.

The Falcon 9 upper stage, which is 14 meters long and weighs roughly 4 metric tons, has remained in a broad orbit around the Earth since February 2015. Because it was impacted by lunar and solar gravity, as well as the Earth's, its precise movements were difficult to anticipate.

However, we now know that it will reach the Earth at a speed of around 2.6 kilometers per second on March 4. This will result in a crater with a diameter of around 19 meters, which has sparked indignation on social media from those who are outraged that the moon will be disfigured in this way as a result of human error.

A dead rocket landing on the Moon, on the other hand, is undoubtedly more environmentally benign than a re-entry burn-up releasing metal oxide particles into the upper atmosphere of Earth. Because the Moon lacks an atmosphere to protect it from space debris, it is constantly acquiring impact craters from natural causes.

In March 2013, the Lunar Reconnaissance Orbiter captured a 19-meter crater produced when a half-ton of asteroid rock traveling roughly 10 times faster than the Falcon 9 hit the surface. NASA's lunar impact monitoring project has detected hundreds of smaller impacts involving bits of rock weighing as little as half a kilogram over the last decade.

We won't be able to witness the coming impact because it will be on the lunar far side. After the impact, however, spacecraft orbiting the Moon will be able to photograph the crater. Will we gain any new knowledge? We know what to expect because there have been several past purposeful moon landings.

On the Apollo landing missions, for example, the rockets' upper stages were crashed in order to examine the lunar interior using vibrations measured by surface seismometers mounted on the surface. There is no way to know if the seismometer aboard China's Chang'e 4 far side lunar lander would be able to offer any helpful data this time, as the Apollo seismometers were shut off long ago.

In 2009, NASA's LCROSS mission shot a projectile into a permanently shadowed polar crater, creating a smaller crater on its icy bottom and releasing a plume that contained the hoped-for water vapour, which proved to be the case.