WASHINGTON: It was, to put it mildly, a bad day on Earth when an asteroid smacked Mexico’s Yucatan Peninsula 66 million years ago, causing a global calamity that erased three-quarters of the world’s species and ended the age of dinosaurs.
The immediate effects included wildfires, quakes, a massive shockwave in the air and huge standing waves in the seas. But the coup de grâce for many species may have been the climate catastrophe that unfolded in the following years as the skies were darkened by clouds of debris and temperatures plunged.
Researchers on Monday (Oct 30) revealed the potent role that dust from pulverised rock ejected into the atmosphere from the impact site may have played in driving extinctions, choking the atmosphere and blocking plants from harnessing sunlight for life-sustaining energy in a process called photosynthesis.
The total amount of dust, they calculated, was about 2,000 gigatonnes – exceeding 11 times the weight of Mt Everest.
The researchers ran palaeoclimate simulations based on sediment unearthed at a North Dakota palaeontological site called Tanis that preserved evidence of the post-impact conditions, including the prodigious dust fallout.
The simulations showed this fine-grained dust could have blocked photosynthesis for up to two years by rendering the atmosphere opaque to sunlight and remained in the atmosphere for 15 years, said planetary scientist Cem Berk Senel of the Royal Observatory of Belgium and Vrije Universiteit Brussel, lead author of the study published in the journal Nature Geoscience.
While prior research highlighted two other factors – sulphur released after the impact and soot from the wildfires – this study indicated dust played a larger role than previously known.
The dust – silicate particles measuring about 0.8-8.0 micrometres – that formed a global cloud layer were spawned from the granite and gneiss rock pulverized in the violent impact that gouged the Yucatan’s Chicxulub crater, 180km wide and 20km deep.
In the aftermath, Earth experienced a drop in surface temperatures of about 15 degrees Celsius.
“It was cold and dark for years,” Vrije Universiteit Brussel planetary scientist and study co-author Philippe Claeys said.