"We saw that the boulders weren't scattered randomly in space," Farnham said. "Instead, they were clustered in two pretty distinct groups, with an absence of material elsewhere, which means that something unknown is at work here."

The largest debris cluster, containing about 70% of the measured objects, was ejected toward the south at high velocities and shallow angles to the surface. The team believes that the ejected boulders likely came from specific sources, perhaps from larger boulders on Dimorphos that were shattered by DART's solar panels just before the main body of the spacecraft hit the surface.

"DART's solar panels likely hit two big boulders, called Atabaque and Bodhran, on the asteroid," explained the paper's second author, Jessica Sunshine, a professor of astronomy and geology at UMD. "Evidence suggests that the southern cluster of ejected material is probably made up of fragments from Atabaque, a 3.3-meter-radius boulder."