Dinosaur-killing asteroid had a distant origin

The asteroid that doomed the dinosaurs came to Earth from a faraway neighborhood, researchers say. In a study published in the journal ScienceResearchers say analysis of isotopes has confirmed that the asteroid, which struck a site called Chicxulub 66 million years ago, was a carbon-rich asteroid that formed in the outer solar system beyond Jupiter. Carbonaceous, or C-type, asteroids strike Earth less often than rocky, silicate-rich S-type asteroids. Researchers discovered signs of S-type asteroids in five other large impacts over the past 500 million years. They say the finding rules out theories that the asteroid was actually a comet.

• A rare metalMario Fischer-Gödde, an isotope geochemist at the University of Cologne, and his team measured isotopes of ruthenium, a metal that is very rare in the Earth's crust. Nature Reports. Based on the distribution of isotopes, they were able to determine whether an asteroid formed in the inner or outer part of the solar system.