Global ocean acidification caused by acid rain occurred just days after a massive asteroid slammed into the Earth 66 million years ago, new research suggests.
The rapid acidification could explain why surface-dwelling organisms such as ammonites and carbon-secreting plankton were wiped out, while some deep ocean dwellers as well as freshwater species such as crocodiles survived one of the largest mass extinction events in history.
Most scientists believe the Cretaceous-Palaeogene mass extinction event, which wiped out 75 per cent of all life on Earth including the non-avian dinosaurs, was triggered by the impact of a 10-kilometre wide asteroid off Mexico's Yucatan Peninsula.
However, questions about why most species were wiped out while some others survived have remained an area of intense debate among scientists.
The impact, which created the 180-kilometre wide Chicxulub crater, covers an area of seabed that contains anhydrite, a sulphur-rich rock.
While it had been hypothesized that acid rain could have caused the extinction patterns, previous work suggested that sulphur dioxide would have stayed in the atmosphere for months - much too long to cause rapid acidification.