Blog

What caused the dinosaurs to go extinct 66 million years ago? Most scientists think an asteroid impact sealed their fate. But others think massive volcanic eruptions in India did the job. Now, scientists from Europe have used chemistry to support the asteroid theory and they can even say where the asteroid came from!

All around the world, rocks that are 66 million years old have an unusual layer called the K-Pg boundary. This thin band of rock marks the end of all the dinosaur fossils. But chemically, there’s something else special about the layer.

This thin, boundary layer contains high levels of elements like iridium, platinum and ruthenium. These elements are rare on Earth’s surface, but they are common in asteroids and can also be brought up by volcanic activity. So where did this layer of rare elements come from?

Chemical clues

To investigate this, European scientists looked more closely at the ruthenium atoms. Some elements come in different isotopes – atoms of the same element that weigh slightly different amounts. The level of one isotope compared to another isotope in a rock can tell scientists where that rock came from. It’s a bit like a chemical fingerprint.

The team of scientists compared the K-Pg boundary’s isotope fingerprint to a range of asteroids and meteorites that hit the Earth, as well as volcanic rocks from India. Using their chemical analysis, they could confidently say the ruthenium atoms in the K-Pg boundary did not come from volcanoes.

But the story doesn’t end there. Asteroids come in different types, based on where they formed and what they’re made of. The isotope fingerprint from the extinction of the dinosaurs matched one type of asteroid really well. This type of asteroid is called carbonaceous, and they formed far out, beyond the asteroid and past the orbit of Jupiter.

Thanks to chemistry, we can imagine an asteroid hurtling in from the outer solar system, slamming into Earth and showering the surface with rare elements.