26, the spacecraft intentionally crashed into the asteroid's small moon, Dimorphos. DART launched in November 2021 and arrived at near-Earth asteroid Didymos in September 2022. This technique works particularly well if used far in advance, since small nudges can add up to big changes later on.ĭART, NASA's Double Asteroid Redirection Test, was the first space mission to test this or any other asteroid deflection technique. The concept is simple: Slam one or more spacecraft into the asteroid at high speed to change its orbit and move Earth out of the crosshairs. Somewhere in between is the kinetic impactor technique. NASA believes the best way to deploy such weapons would be at a distance, to impart force without blowing the asteroid to smithereens, which could further imperil Earth.What should we do if we find a dangerous asteroid on course to hit Earth? There are a number of possible deflection techniques, ranging from extreme (a nuclear blast) to benign (a heavy spacecraft uses gravity to nudge the asteroid off-course). Should an approaching object be detected early, a spaceship could be sent to fly alongside it for long enough to divert its path by using the ship’s gravitational pull, creating a so-called gravity tractor.Īnother option would be launching nuclear explosives to redirect or destroy an asteroid. Kinetic impact with a spaceship is just one way to defend the planet, albeit the only method possible with current technology. The geological record shows, for example, that a 9.6km (6 mile) wide asteroid struck Earth 66m years ago, plunging the world into a long winter that led to the mass extinction of the dinosaurs along with 75 percent of all species.Īn asteroid the size of Dimorphos, by contrast, would only cause a regional impact, such as devastating a city. But wait long enough, and it will happen. Very few of the billions of asteroids and comets in our solar system are considered potentially hazardous to our planet, and none is expected to hit in the next 100 years or so. Its egg-like shape and craggy, boulder-dotted surface finally came into clear view in the last few moments as DART raced towards it at roughly 23,500km/h (14,500 mph). Never actually photographed before, Dimorphos appeared as a speck of light about an hour before impact. But if it is “fluffy” and significant mass is pushed at high velocity in the opposite direction to impact, there will be an additional boost. If an asteroid is more solid, the momentum imparted by a spaceship will be limited. ‘Rubbish pile’Īhead of the test, NASA scientists said the results of the experiment would reveal whether the asteroid is a solid rock, or more like a “rubbish pile” of boulders bound by mutual gravity. The binary asteroid system, which was about 11m km (6.8m miles) from Earth at impact, is visible only as a single dot from the ground. Thanks to its temporary new tail, Dimorphos, which is 160 metres (530-foot) in diameter or roughly the size of a big Egyptian pyramid, has turned into a man-made comet.īut quantifying just how well the test worked required an analysis of light patterns from ground telescopes, which took a few weeks to become apparent. ![]() “I grew up watching Armageddon and Deep Impact and all that, and it is amazing to see this stuff become a reality,” Cendes said. The pictures were collected by Earth and space telescopes as well as a satellite that had travelled to the zone with DART. DART’s success as a proof-of-concept has made a reality of science fiction.Īstronomers rejoiced in stunning images of matter spreading out thousands of kilometres in the wake of the impact.
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