An intense debate surrounding the cosmic rock that killed the dinosaurs has stirred scientists for decades, but a new study has revealed some important—and far-out—data about the impactor’s origin story.

Researchers measured the isotopes of the element ruthenium, not uncommon on asteroids but extremely rare on Earth. So by inspecting the deposits in multiple geological layers that mark the debris from the impact at Chicxulub, they could be sure that the ruthenium studied came “100 percent from this asteroid.”

Scientists believe water may have been brought to Earth by asteroids, likely of the C-type like the one that struck 66 million years ago, even though they are less frequent.