Previous studies have posited that the mass extinction that wiped the dinosaurs off the face of the Earth was caused by the release of large volumes of sulfur from rocks within the Chicxulub impact crater 66 million years ago. A new study questions this scenario. Using groundbreaking empirical measurements of sulfur within the related Cretaceous-Paleogene (K-Pg) boundary layer, the international team has demonstrated that the role of sulfur during the extinction has been overestimated.