NASA is about to slam a spaceship into an asteroid about the size of the Great Pyramid of Giza in an attempt to alter its course. The project, part of NASA's Planetary Defense remit, aims to test whether the method could be used in the event of an asteroid on a collision course with Earth.
The Double Asteroid Redirection Test (DART) is expected to impact asteroid Dimorphos at 7:14 pm EDT on Monday, September 26, as the object makes its closest approach to Earth. Unlike in most major asteroid movies, the vending machine-sized spacecraft, which launched in November 2021, will autonomously navigate its way to impact, and be entirely Bruce Willis-free.
In order to measure the impact of the $330 million spacecraft, scientists at Johns Hopkins University Applied Physics Laboratory will look closely at how long it takes for moonlet Dimorphos to orbit its parent asteroid Didymos, before and after impact. If the 24,100-kilometers-per-hour (15,000 miles per hour) collision has been successful, the asteroid will complete its orbit in a shorter time period. The Lowell Discovery Telescope in Flagstaff, Arizona has been keeping a close watch on the orbital path of Dimorphos for this very reason.
“The before-and-after nature of this experiment requires exquisite knowledge of the asteroid system before we do anything to it,” astronomer at Lowell Observatory Nick Moskovitz told NASA. “We don’t want to, at the last minute, say, ‘Oh, here’s something we hadn’t thought about or phenomena we hadn’t considered.’ We want to be sure that any change we see is entirely due to what DART did.”
The team needs to be sure that the orbit has been altered by the impact itself, and not other factors such as the Sun heating one side of the asteroid, which can alter the trajectory of the object to such an extent that it's been suggested we could spray-paint an asteroid that was heading our way.
NASA hopes that DART will help it gauge the effectiveness of slamming spacecraft into potentially-hazardous asteroids, and allow them to "assess how best to apply it to future planetary defense scenarios".
If the test is successful, and a planet-killer asteroid (or smaller) is found to be heading towards Earth, there's a chance that one day we could end up Bruce Willis-ing it out of our way.