Update: The NASA spacecraft DART intentionally slammed into the asteroid Dimorphos at 14,000mph on Monday. It could be weeks, however, before NASA knows how much the impact changed the path of the asteroid, the AP reports. Telescopes on Earth and in space were pointed at the spot in anticipation; Dart's radio signal ceased on impact. NASA Administrator Bill Nelson said earlier Monday that though the event might seem like something out of Hollywood, it's not. "We've all seen it on movies like Armageddon, but the real-life stakes are high," he said in a prerecorded video. Our story from Saturday follows:
NASA is about to clobber a small, harmless asteroid millions of miles away, all in the name of practicing how to save the world. A spacecraft named DART will zero in on the asteroid Monday, intent on slamming it head-on at 14,000mph, per the AP. The impact should be just enough to nudge the asteroid into a slightly tighter orbit around its companion space rock—demonstrating that if a killer asteroid ever heads our way, we'd stand a fighting chance of diverting it. Cameras and telescopes will watch the crash, but it will take months to find out if the impact actually changed the orbit. The $325 million planetary defense test began with DART's launch last fall.
The asteroid with the bull's-eye on it is Dimorphos, about 7 million miles from Earth. It's actually the puny sidekick of a 2,500-foot asteroid named Didymos, Greek for "twin." Discovered in 1996, Didymos is spinning so fast that scientists believe it flung off material that eventually formed a moonlet. Dimorphos—roughly 525 feet across—orbits its parent body at a distance of less than a mile. "This really is about asteroid deflection, not disruption," said Nancy Chabot, a planetary scientist and mission team leader at Johns Hopkins University, which is managing the effort. "This isn't going to blow up the asteroid." Rather, the impact will dig out a crater tens of yards in size and hurl some 2 million pounds of rocks and dirt into space.
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Although the intended nudge should change the moonlet's position only slightly, that will add up to a major shift over time, according to Chabot. "So if you were going to do this for planetary defense, you would do it five, 10, 15, 20 years in advance in order for this technique to work," she said. Even if DART misses, the experiment still will provide valuable insight, said NASA program executive Andrea Riley. "This is why we test. We want to do it now rather than when there's an actual need." (More asteroid stories.)
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