The Asteroid That Killed the Dinosaurs Hit a "Sweet Spot" for Mass Extinction
A new modeling study suggests that the infamous Chicxulub impactor triggered the end-Cretaceous mass extinction not just because it was large, but because it hit the wrong part of the planet.
A 2017 study suggests that only about 13% of Earth's surface contained the right kind of rock to generate the catastrophic climate effects that ended the dinosaur era.
The "Perfect Storm" Scenario
The study, led by Kunio Kaiho and Naga Oshima (2017), proposes that the extinction was driven by massive amounts of soot. This soot was generated when the asteroid struck shallow tropical seabed rich in hydrocarbons. The resulting stratospheric soot blocked sunlight, causing a severe "impact winter."
The model indicates that this impact would have caused global cooling of 8–11°C and a sharp reduction in rainfall.
The paper argues that an asteroid of the same size hitting most other parts of the planet—where hydrocarbon-rich rock was scarce—would not have triggered a mass extinction.
The Established Context
While the asteroid impact at Chicxulub is a well-established event (first proposed by Luis and Walter Alvarez in 1980, with the crater later identified), the soot mechanism is just one of several proposed drivers of the extinction.
- Some research emphasizes sulphate aerosols or silicate dust as the primary kill mechanism.
- A 2020 study by Gareth Collins et al. suggested the asteroid struck at a steep angle (~60°), which may have increased the amount of climate-altering ejecta.
- The role of the Deccan Traps volcanic eruptions in the extinction remains a heavily debated factor.
Important Limitations
While compelling, the study carries significant caveats:
- Model Dependency: The 13% figure is a model output based on reconstructed late Cretaceous geology, not a direct measurement.
- Scientific Debate: The soot-driven cooling hypothesis is not universally accepted; other cooling mechanisms are actively studied and modeled.
- Counterfactual: The argument is inherently counterfactual and cannot be directly tested by experiment.