Astronomers predict that a SpaceX rocket launched nearly seven years ago will crash into the moon.
The Falcon 9 booster was launched in February 2015 as part of a mission to carry a climate observation satellite 930,000 miles (1.5 million kilometers) from Earth, but it has been flying about space in a chaotic orbit since running out of fuel.
The orbit of the spent second stage is now on course to collide with the Moon, according to sky observers. Such an impact, according to Bill Gray, the creator of the widely used Project Pluto program for tracking near-Earth objects, asteroids, minor planets, and comets, might occur in March.
Gray asked amateur and professional astronomers to make more observations of the stage, which looks to be drifting across space, earlier this month. He projects that the Falcon 9's upper stage will most certainly contact the far side of the Moon on March 4, near the equator, based on new data.
Gray wrote on his blog on Jan. 21 that the space junk "made a close lunar flyby on Jan. 5" but is on track for "a certain impact on Mar. 4."
"This is the first unintentional case [of rocket debris hitting the moon] of which I am aware," Gray wrote.
The now-defunct booster was launched into space as part of SpaceX's inaugural deep-space mission. The Deep Space Climate Observatory, a spacecraft meant to monitor both solar storms and the Earth's climate, was launched to a gravitationally stable Lagrange point between the sun and the Earth. The rocket's second stage ran out of fuel after completing its mission and began tumbling around Earth and the moon in an erratic orbit.
Jonathan McDowell, an astronomer at Harvard University, confirmed the rocket's Mar. 4 collision on Twitter. While the impact was "interesting," he noted, it was "not a big deal."
The long, cylindrical rocket is expected to crash somewhere around the moon's equator on its far side, which means the impact will likely go unnoticed. However, its course is uncertain and could be influenced by a variety of circumstances, including solar radiation pressure, which could lead the rocket to teeter sideways.
A good prediction of where the space litter will land is crucial because it may allow satellites 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.
