Space mystery: Scientists believe old rocket hardware hit the moon, but there's no proof

The moon is seen in this file photo. (Bruno Scramgnon/Pexels)

Scientists believe a roughly four-ton discarded rocket has slammed into the moon while travelling at 9,300 kilometres per hour. However, there is no proof yet of the impact.

Astronomers say the space junk, which had been hurtling through space for years, hit the moon's far side, meaning it could take months to find.

According to orbital calculations on speed and trajectory using Earth-based telescopes, the old rocket crashed into the moon in a large, existing crater on Friday at 7:25 a.m. EST. In part because it hit the far side of the moon, the strike wasn't directly observed by astronomers.

Scientists say the rocket is expected to have created a crater within the existing crater approximately 10 to 20 metres across, roughly the size of a basketball court.

To know exactly where the rocket hit, astronomers will need satellite images, but NASA's Lunar Reconnaissance Orbiter and India’s Chandrayaan-2, which both orbit the moon, were not in a position to observe the impact as it happened. Both probes are only able to observe any region on the Moon once a month.

However, NASA says the orbiter's mission team is assessing whether observations can be made by any changes to the lunar environment following the time of the impact. With this, the space agency said it may be able to later identify the crater formed by the impact.

Astronomer Bill Gray, an independent contractor who has created orbital calculation software used by NASA, was the first to identify the old rocket back in 2015. Gray tracks space junk to ensure scientists do not confuse them with asteroids.

According to Gray, he initially thought the space junk was a SpaceX rocket. Upon deeper analysis, he concluded it was a discarded rocket booster from China's Chang'e 5-T1 mission in 2014. Chinese officials disagree and claim the booster burned up in re-entry to Earth's atmosphere years ago.

However, the U.S. Department of Defence's Space Command, which tracks low-Earth orbiting space junk, released a statement Tuesday saying China's 2014 rocket never deorbited.

While it is not unusual for leftover rocket parts to be abandoned in space after helping launch a spacecraft, scientists note this hit marks the first time an unintentional collision with the moon had been projected.

Scientists have intentionally crashed rocket stages into the moon before, including during the Apollo missions to study seismometers.