A SpaceX rocket that launched nearly seven years ago is now on course to crash into the moon, astronomers have predicted.
The Falcon 9 rocket was launched in February 2015 as part of a mission to send a climate observation satellite 930,000 miles (1.5 million kilometers) from Earth, but since running out of fuel, the 4.4-ton (4 metric tons) rocket has been hurtling around space in a chaotic orbit.
The rocket's upper stage is now expected to hit the far side of the moon while traveling at a blistering speed of 5,771 mph (9,288 km/h) on March 4, 2022, according to Bill Gray, a developer of software that tracks near-Earth objects.
In a Jan. 21 blog post, Gray noted that the space junk had "made a close lunar flyby on January 5" but is set for "a certain impact at March 4."
"This is the first unintentional case [of rocket debris hitting the moon] of which I am aware," Gray wrote.
The now-defunct booster stage was sent into space as a part of SpaceX's first deep-space mission. The company launched the Deep Space Climate Observatory, a satellite designed to monitor both solar storms and Earth's climate, to a gravitationally stable Lagrange point between the sun and Earth. After completing its task, the rocket's second stage ran out of fuel and began tumbling around Earth and the moon in an unpredictable orbit.
Jonathan McDowell, an astrophysicist at Harvard University wrote on Twitter confirming the rocket’s March 4 impact. He wrote that while the impact was "interesting" it was "not a big deal."
Gray has forecast that the long, cylindrical rocket stage should land somewhere around the moon's equator at its far side, meaning that the impact will likely go unobserved. But its trajectory isn't certain and could be altered by a few factors, including radiation pressure from sunlight, which could cause the rocket to tumble sideways.
"Space junk can be a little tricky," Gray wrote in the blog post. "I have a fairly complete mathematical model of what the Earth, Moon, Sun and planets are doing and how their gravity is affecting the object. I have a rough idea of how much sunlight is pushing outward on the object, gently pushing it away from the Sun … However, the actual effects of that sunlight are hard to predict perfectly. It doesn't just push outward; some of it bounces 'sideways.'"
A good prediction of where the space litter will land is important because it could enable satellites currently orbiting the moon, such as NASA's Lunar Reconnaissance Orbiter and India's Chandrayaan-2 spacecraft, to observe the moon’s subsurface contents revealed by the impact crater, or even observe the impact itself.
This isn't the first time a human-made satellite has crashed into the moon. In 2009, NASA's Lunar Crater Observation and Sensing Satellite was fired into the moon's south pole at 5,600 mph (9,000 km/h), unleashing a plume that allowed scientists to detect the key signatures of water ice.
Originally published on Live Science
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Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.