The mass extinction of the dinosaurs, approximately 66 million years ago, may have been caused by the ejection of soot into the atmosphere following the Chicxulub asteroid impact, according to a paper published in Scientific Reports.

It has been suggested that the Chicxulub asteroid impact was responsible for the extinction of the dinosaurs by causing the formation of condensed sulphuric acid aerosols in the stratosphere. The aerosols produced acid rain and reflected sunlight causing global darkness, which led to a reduction in photosynthesis and near freezing conditions. However, under this scenario crocodilians would have been made extinct as well. Experiments have also concluded that condensed sulphuric acid aerosols cannot form and persist over long periods following asteroid impacts.

Kunio Kaiho and colleagues examined sediments from the boundary of the Cretaceous and Paleogene periods (approximately 66 million years ago) from Haiti and Spain. By analysing the hydrocarbons found in these samples, the authors suggest that the asteroid impact into an oil rich area of Mexico launched a cloud of smoke into the atmosphere, which spread globally. Based on the hydrocarbons found in their samples and climate models, they suggest that a soot ejection of approximately 1,500 teragrams would have been sufficient to cause the mass extinction of dinosaurs, while allowing animals such as crocodilians to survive.

The authors argue that soot in the atmosphere produced colder climates at mid-high latitudes leading to the extinction of most species in these regions. However, droughts accompanied by mild cooling at lower latitudes would have led to the extinction of the dinosaurs but allowed crocodilians to survive.