Sulphur-rich vapour resulting from the Chicxulub asteroid impact 65 million years ago in the Yucatan Peninsula, Mexico, could have rapidly acidified the oceans, reports a study published online in Nature Geoscience. The findings could explain the extinctions of near-surface marine species and the preferential survival of deep-ocean dwellers at the time.
Sohsuke Ohno and colleagues conducted impact experiments into anhydrite, a sulphur-rich rock that is found at the site of the Chicxulub impact, and analysed the composition of the resulting vapour cloud. They found that at impact velocities similar to those expected when an asteroid hits the Earth, the sulphur in the anhydrite would have been vapourized to sulphur trioxide, which reacts quickly with atmospheric water vapour to form sulphuric acid aerosols. The authors suggest that the sulphuric acid aerosol particles would have stuck to heavier particles of debris that were ejected from the impact site. As a result, the sulphuric acid aerosols would have been deposited on the surface within just a few days, much faster than previously suggested. This rapid delivery of sulphuric acid to the Earth’s surface would have caused severe acidification of the surface oceans and would have had deleterious effects on marine life.