https://www.nature.com/articles/d41586-023-00601-4
One factor is that the spacecraft hit a spot around 25 metres from the asteroid’s centre, maximizing the force of its impact. Another is that large amounts of the asteroid’s rubble flew outwards from the impact. The recoil from this force pushed the asteroid further off its previous trajectory. Researchers estimate that this spray of rubble meant Dimorphos’ added momentum was almost four times that imparted by DART4.
Although NASA has demonstrated this technique on only one asteroid, the results could be broadly applicable to future hazards, researchers say. “It means that we can quickly design a mission to deflect an asteroid if there is a threat, and we know that this has a very high chance of being effective,” says Franck Marchis, from the SETI Institute in Mountain View, California who is also chief scientific officer at the telescope manufacturer Unistellar in Marseille.
“If you had asked me 30 years ago, ‘Can we be confident we won’t be wiped out by a giant killer asteroid a week from next Tuesday?’ I would have had to say no,” adds Tom Statler, DART’s programme scientist at NASA headquarters in Washington DC. Now that astronomers have surveyed the skies to identify nearly all the dangerous asteroids — and now that DART has been shown to work —“we will know what to do about it when something new is found”, he says.