Asteroid That Killed The Dinosaurs Was A Carbon-Rich Rock

RACHEL FELTMAN: This is Science Friday. I’m Rachel Feltman. Around 66 million years ago, an asteroid slammed into the Earth, spewed dust and rock everywhere, plummeted the planet into cold darkness, and ended the age of dinosaurs. It might be the most famous natural disaster in our planet’s history, but scientists still have plenty of questions about it like, What was the asteroid made of? and where did it come from? A new study in the journal Science offers up some long-awaited answers. Lead author Dr. Mario Fischer-Godde is a geochemist at the University of Cologne in Germany. Welcome to Science Friday.

MARIO FISCHER-GODDE: Yeah, hi there. Many thanks for having me.

RACHEL FELTMAN: So let’s get into it. Were you able to figure out what the asteroid was made of?

MARIO FISCHER-GODDE: Yes, we definitely found an answer to this because we could show with our new study that it was a carbonaceous-type asteroid. That’s asteroids that formed further out in the solar system, initially beyond the orbit of Jupiter, and they contain higher amounts of water, carbon and nitrogen compared to S-type asteroids, which are silicious-type asteroids that are composed out of silicate and metal, and they formed more in the inner solar system.

And our new data show that the Chicxulub impactor was a carbonaceous-type asteroid.

RACHEL FELTMAN: So the Chicxulub impactor that killed the dinos was basically like a flaming, carbon-rich ball of rock, right?

MARIO FISCHER-GODDE: Yeah, when it entered the Earth’s atmosphere, of course, it was already starting to flame up, and when it smashed into the crustal rocks, then everything got vaporized at second, yeah.

RACHEL FELTMAN: So is this composition pretty typical, or did this asteroid stand out?

MARIO FISCHER-GODDE: Of course, the Chicxulub impact, as you mentioned, is one of the most famous impacts. We wanted to compare this asteroid impact to other impacts on Earth. And what our study also shows that within the last 500 million years, this Chicxulub impact is really a rare case of a C-type asteroid hitting the Earth because all other impact structures that we investigated, they clearly match the compositions of S-type asteroids. So this is a really unique event so far.

RACHEL FELTMAN: Wow. So the dinosaurs got taken out by a pretty rare kind of impact. That’s unlucky for them but maybe kind of lucky for us. Mario, I’m assuming we didn’t actually have chunks of the dino-killing asteroid in question at hand to study, so how did you even figure this out?

MARIO FISCHER-GODDE: Yes, when the asteroid impacted on Earth, we had a huge impact plume that developed, and the particles, dust particles, were dispersed into the atmosphere, and they could distribute all around the globe, basically. And then the particles were deposited into sedimentary layers that formed exactly 66 million years ago, and these sediment layers, they can be sampled.

I was not the rock-hunting guy in this study. Some of my colleagues did that, actually. They did a great job, and they provided me with samples.

RACHEL FELTMAN: Very cool. So do we know where in the solar system this asteroid came from?

MARIO FISCHER-GODDE: These C-type asteroids are interpreted to have formed beyond the orbit of Jupiter, and this is because they contain a lot of volatile elements, and these volatile elements could not condense closer to the sun because the temperatures in the inner solar system were too hot to allow for the condensation of, let’s say, water or something like that. And that’s why water and other volatile elements were incorporated only in asteroids that formed beyond what we call the snow line, and they are the volatile elements could be incorporated in this C-type asteroid material.

RACHEL FELTMAN: So I know that when we talk about space objects that are from this long ago, there’s always the hope that they can tell us something about the early days of our solar system and even how it came to be. Can this asteroid teach us any of those lessons?

MARIO FISCHER-GODDE: In principle, it could. However, we have asteroid samples in form of small fragments arrive on Earth as meteorites. And this material, of course, we can study in our laboratories, and from this material, we know that this C-type asteroid material is very volatile rich. Especially it can contain up to 20% of water. And the basic idea is that the Earth primarily formed from silicious-type asteroid material, but in order to explain our water abundance on Earth, at some stage during the accretion of the Earth, we would have needed such C-type asteroid material incorporated to our planet in order to explain the water on Earth.

By studying these asteroids, we can learn about the principal building blocks of our planets.

RACHEL FELTMAN: What other big questions do you have about asteroids, and what research is next for you?

MARIO FISCHER-GODDE: So during the last 500 million years in Earth’s history, there were several major mass-extinction events, and some of them are also thought to have been caused by an asteroid impact. And one of our future research tasks will be to eventually find traces of such impact events that could have also led to major mass-extinction events in earlier days of the Earth.

Another topic we will investigate at the University of Cologne is, for instance, we have a look at the moon. We see a heavily cratered surface, and the lunar surface is 4.4 billion years old. So it provides a collection of asteroid material that impacted onto the moon some billion years ago, and the same material would have also hit the Earth at that time. So we can also learn, by studying these ancient lunar impact rocks, we can learn about what asteroid type was hitting the Earth in its very early days and if this material could have delivered water to Earth.

RACHEL FELTMAN: Mario, thanks so much for joining me.

MARIO FISCHER-GODDE: Yeah, many thanks for having me.

RACHEL FELTMAN: Dr. Mario Fischer-Godde is a geochemist at the University of Cologne in Germany.

Copyright © 2024 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of Science Friday’s programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies/