Experts predict that a piece of a SpaceX rocket that launched seven years ago and was left in space after completing its mission will fall onto the Moon in March.
The rocket was launched in 2015 to launch the Deep Space Climate Observatory, a NASA satellite (DSCOVR).
According to astronomer Bill Gray, the rocket's second stage, or booster, has been drifting in what mathematicians term a chaotic orbit since then.
Gray was the one who computed the new crash route of the space junk with the Moon. According to Gray, the launcher came quite close to the Moon in January, altering its orbit.
He is the creator of Project Pluto, which is used in NASA-funded space observation programs to determine the route of asteroids and other objects in space.
Gray watched the rocket stage again a week after it zoomed close to the Moon and concluded it would crash on the Moon's dark side on March 4 at speeds of over 9,000 kilometers per hour (5,500 mph).
Gray enlisted the help of amateur astronomers to observe the rocket, and his conclusion was validated.
Although the actual time and site of impact may differ somewhat from what he predicted, there is universal agreement that a collision will occur on that day.
"I've been following this type of garbage for almost 15 years. And this is the first time we've had an unintended lunar impact," Gray explained.
It's Time To Regulate
However, according to astronomer Jonathan McDowell, the collision's effects will be small, and that comparable collisions may have occurred previously unobserved.
"There are at least 50 items in deep Earth orbit that were simply abandoned in the 1960s, 1970s, and 1980s." "We didn't follow them," he explained.
"Right now, we're picking up a few of them... "However, we're not discovering a lot of them, so they're no longer there," he continued. "I'm sure at least a couple of them accidently struck the moon, and we just didn't notice."
The impact of a four-tonne part of SpaceX rocket on the Moon will not be visible in real time from Earth.
However, it will create a crater that scientists will be able to monitor with spacecraft and satellites like NASA's Lunar Reconnaissance Orbiter or India's Chandrayaan-2, allowing them to learn more about the Moon's geology.
For scientific purposes, spacecraft have been purposely crashed onto the Moon before, such as during the Apollo missions to test seismometers.
NASA sent a rocket stage into the Moon near its south pole in 2009 to search for water.
However, most rockets do not travel that far from Earth. SpaceX returns their rocket boosters to the surface of the Earth, where they disintegrate over the ocean. The first stage of the process is recovered and repurposed.
According to Gray, as the US and Chinese space programs, in particular, leave more debris in orbit, there may be more inadvertent crashes into the Moon in the future.
The United States is already planning a space station to circle the Moon with foreign partners.
These events "become problematic when there's a lot more traffic," according to McDowell.
"Keeping track of the garbage we leave out in deep earth orbit is actually no one's job," he remarked. "I believe the moment has come to start regulating it."
A request for comment from SpaceX was not immediately returned.
Elon Musk's business is working on a lunar lander that will allow NASA to send astronauts back to the Moon as soon as 2025.
