Study Links Dinosaur Extinction to Carbon-Rich Asteroid

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Facts

• Researchers from Germany's University of Cologne have found evidence that the rock that hit Earth 66M years ago, causing the extinction of the dinosaurs, was a carbon-rich 'C-type' asteroid that formed beyond Jupiter's orbit around the same time as the Solar System.^[1][2]
• By analyzing the remains of the crater where the asteroid hit Earth in what is now Mexico, called the Chicxulub impact, the scientists discovered the isotope ruthenium, which is commonly found in asteroids but not in the Earth's crust.^[2]
• They compared debris from the Chicxulub impact that they found in Italy, Spain, and Denmark to rocks from eight other impact sites that were made over the last 3.5B years.^[1][3][4]
• Ruthenium is found in celestial rocks called carbonaceous chondrites, which link back to the beginning of the Solar System about 4.6B years ago. They're also rich in carbon, water, and other volatile molecules that can vaporize, meaning they likely formed far away from the Sun in the outer Solar System.^[4]
• The evidence of ruthenium goes against a previous theory that it was a comet — broken up by the Sun's gravitational pull — that hit the Chicxulub impact site.^[3]
• The carbon levels of carbonaceous chondrites show they were likely what caused the cloud of dust that blocked out the Sun and killed the dinosaurs. However, lead study author Mario Fischer-Gödde said it would be helpful to collect samples of comets to completely rule them out.^[4]

Sources: ^[1]Guardian, ^[2]New York Times, ^[3]Nature and ^[4]Science.

Narratives

• Narrative A, as provided by Ars Technica. The comet theory was understandable given the prevalence of carbonaceous chondrites in long-period comets, but the discovery of ruthenium proves it was more likely to have been an outer Solar System asteroid. The rocks from the impact site were from C-type asteroids, while most of the others were S-type, which are from the inner Solar System.
• Narrative B, as provided by Big Think. While scientists appear to have finally found the cause of the dinosaur's abrupt extinction, the species was likely on its way out — albeit at a slower rate — without the help of a celestial attack. At the time, the Earth was cooling, thus turning widespread tropical climates into a less vegetative climate. Dinosaurs, like most species throughout Earth's history, were slowly losing their food source.