Chicxulub Asteroid Sparked Global Firestorm, Study Finds
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- Brandon Johnson at Purdue University and colleagues analyzed geological observations and lab impact simulations, finding the Chicxulub strike vaporized about 5x more material than previously estimated — over 1,000 cubic kilometres of rock in roughly one second.
- The vapor plume expanded tens of thousands of kilometres above Earth's atmosphere, condensing into 1.6 trillion tonnes of dust that blanketed the planet and trapped heat.
- Heavier glassy, metallic spherules re-entered the atmosphere over subsequent hours, creating an approximately hour-long pulse of thermal radiation intense enough to ignite grass, pine needles, and potentially trees, according to the study.
- Cretaceous animals received 17 times the thermal radiation dose that is 100% lethal to humans — enough, Johnson says, to kill off even thick-skinned dinosaurs.
- Craig O'Neill at Queensland University of Technology says the dust layer was essentially opaque to infrared and visible light, trapping heat and baking Earth's surface for about 30 minutes — 'history's largest barbecue.'
- Marine extinctions of mosasaurs and ammonites are better explained by the nuclear-winter effects of sunlight blocked from photosynthesising organisms than by the thermal pulse, O'Neill notes, suggesting mass extinctions were a 'cascading system of failures' rather than a single cause.
- The study was published in the Journal of Geophysical Research Biogeosciences.
Why it matters: It reframes the dinosaur extinction as a cascade, not a single 'murder weapon': a global thermal pulse from re-entering spherules baked land-dwelling animals within an hour, while subsequent dust-induced darkness starved marine photosynthesis-based ecosystems — meaning the kill sequence had at least two distinct, geographically differentiated phases rather than one unified mechanism.
