An artist's impression of a large Asteroid impacting at Chicxulub on the Mexican coastline, which caused the end-Cretaceous mass extinction, 66 million years ago.

Scientists may have finally found where the object that wiped out the dinosaurs came from.

The mass extinction event that occurred 66 million years ago – the most recent on Earth – came about when a rare kind of asteroid collided with Earth, researchers say.

In that incident, about 60 per cent of the Earth’s species including all of its non-avian dinosaurs were wiped out. Researchers believe that it led to a horrific period in the planet’s history, during which its planets were lit on fire, the Earth was covered in ash and the climate would have turned deadly.

And it all began in the distant outer solar system, beyond Jupiter. There, a C-type asteroid formed that would give rise to what scientists call the Chicxulub impactor, which crashed into Earth and left the vast crater after which it is named.

Scientists say the discovery should help solve long arguments about the history of the Earth, as well as the objects that have collided with it from elsewhere in space.

They came to those conclusions after looking at samples taken from around the same period in which the mass extinction event happened, between the Cretaceous and Paleogene eras. They also looked at samples from five other asteroid impacts taken in the last 541 million years, as well as ancient remnants from impacts billions of years ago.

Layers of the Earth from around the same period tend to be rich in platinum group elements, or PGEs, such as iridium, ruthenium, osmium, rhodium, platinum, and palladium. Those elements are generally rare on Earth, but common in meteorites, though they appear to have spread widely during the collision because they are found right across the Earth.

Researchers looked for the Ru isotope signatures in their samples, which would be a remnant of PGEs. And they found that those taken around the time of the extinction were largely uniform and seemed indicative of carbonaceous chondrites, an unusual kind of meteorite.

That in turn suggests that the Chicxulub impactor formed in the distant solar system and was not a comet, the researchers say.

What’s more, the ancient samples also included some hints of a similar composition. That suggests that as the Earth was forming, it was hit by other objects from the outer solar system.

The other more recent samples appeared to indicate that those collisions had been with S-type, or salicaceous, asteroids, which form in the inner solar system.

A study reporting the findings, ‘Ruthenium isotopes show the Chicxulub impactor was a carbonaceous-type asteroid’, is published in the journal Science.

The Independent