When the NASA DART mission slammed into a small asteroid, we knew with great precision how much the spacecraft weighed and how fast it traveled. If you combine that with our estimates of the motion and mass of its target asteroid, Dimorphos, then you could easily do the math and estimate how much momentum would be lost by the asteroid and what that would mean for its orbit. That bit of math would suggest that Dimorphos’ orbit should end up roughly seven minutes shorter.
Instead, the orbit was shortened by a half hour—over four times that number.
Today’s issue of Nature contains five articles that collectively reconstruct the impact and its aftermath to explain how DART’s collision had an outsized effect. And, in the process, the articles indicate that impactors like DART could be a viable means of protecting the planet from small asteroids.