Perhaps the catastrophe that caused the extinction of the dinosaurs was worse than previously thought

Artist's rendering of Chicxulub impact (Immagine Donald E. Davis/NASA/JPL)
Artist’s rendering of Chicxulub impact (Immagine Donald E. Davis/NASA/JPL)

An article published in the magazine “Geophysical Research Letters” describes a research that offers a new estimate of the climate changes caused by the meteorite that about 66 million years ago led to the extinction of dinosaurs and a lot of other species of the time. According to a team of researchers the amount of sulfur released in the atmosphere was greater than the previous estimates with worse consequences. Part of the authors also participated in drills into the crater caused by the meteorite, which results are described in an article published in the magazine “GSA Today”.

Early in 2017 an article published in the journal “Geophysical Research Letters” described a previous study on that mass extinction and provided some estimates of the impact of that giant meteorite. Now another team of researchers updated those estimates by reviewing through computer simulations the mechanisms that allow an impact to have global effects with the release of gases that have an impact on the climate.

In spring 2016, a team of geologists of the International Ocean Discovery Program and International Continental Scientific Drilling Program (IODP-ICDP) Expedition 364 conducted an expedition to drill off today’s Mexico coast in the crater called Chicxulub generated by the meteorite. Various drills, indicated with various acronyms in the bottom image, occurred in the crater’s peak ring, formed following the rebound of the rocks after the collision that followed the impact, and in other areas of the crater.

The drills confirmed that the peak ring consists of granite, lifted from the depths as a result of the impact. The analyzes of the samples taken allowed to collect new data on the impact of that meteorite which allowed researchers to make new estimates of the amount of sulfur and carbon dioxide that were projected into the atmosphere. The estimates include a second phase of that catastrophe, with a further gas release when the ejected materials were vaporized.

According to the new estimates, about 325 gigatons of sulfur and 425 gigatons of carbon dioxide were ejected into the atmosphere. The amount of sulfur is much higher than that estimated in the previous research. Using the old estimates, the researchers calculated that this impact caused an average global temperature drop up to 26° Celsius for about three years.

The new research didn’t offer any new calculations of that type but sulfur gas must have blocked a considerable percentage of sunlight so a greater amount in the atmosphere means that the cooling was greater. The new simulations also took into account the gases projected at low-speed into the atmosphere that didn’t remain there and didn’t affect the climate.

Despite the devastation, the research into the Chicxulub crater shows fossil traces dating back to the period soon following the impact in the limestone rock. Those traces indicate that about 30,000 years after that event life in that area had already recovered. In essence, new information gathered and more sophisticated simulations are giving us a more complete picture of a key moment in the history of life on Earth.

Scheme of Chicxulub crater (Image courtesy Kring et al)
Scheme of Chicxulub crater (Image courtesy Kring et al)

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