- A massive asteroid hit Mexico today 66 million years ago. The impact contributed to the extinction of dinosaurs and 75% of life on Earth at that time.
- The collision of asteroids caused a great tsunami, forest fires and the release of billions of tons of sulfur, which sank into the sun and caused the planet to cool, killing many terrestrial species.
- A new study reveals that marine species have not been spared: Acid rain and fallout have acidified the world's oceans in a "flash". This caused marine ecosystems to collapse.
- Visit Business Insider's homepage for more stories.
About 66 million years ago, an asteroid over 6 miles wide hit modern-day Mexico. The strike sparked fires that stretched hundreds of miles, triggered a mile-high tsunami and released billions of tons of sulfur into the atmosphere.
Within a minute of striking Earth, the Chicxulub asteroid drilled a hole nearly 1
Read more: For the first time, a timeline reveals what happened minutes and hours after the asteroid crash that killed dinosaurs
While scientists knew catastrophic events after the impact of the asteroid, it caused the mass extinction of 75% of Earth's life (including dinosaurs), the mechanism by which ocean species died less secure. Now, a study in the journal Proceedings of the National Academy of Sciences finds that acid rain barrage after impact is likely the killer.
After the crash of the asteroid, the study authors wrote, the oceans undergo rapid and intense acidification. This destroyed the marine food webs and caused mass extinction.
"It's lightning acidification and has transformed ecosystems for millions of years," Noah Planavsky, one of the study's authors, told the New York Times.
Small Fossil Shells Reveal What Happened After the Impact
To unravel the mystery of what happened after the fatal asteroid catastrophe, scientists examine rocks that were deposited during or after the impact or looking for the fossils of creatures that died when Chicxulub struck.
In this case, the study's lead author, Michael Henehan, discovers exposed clay layers in the Geulhemmerberg Cave in the Netherlands. The clay contains rocks dating from the time before the impact and from the moment after the crash. The rocks in each layer hold fossilized shells of microscopic plankton called foraminifera.
Henehan and his team were able to investigate the levels of chemical isotopes in these shells that provide clues for the death of plankton.
The Henahan team finds that the proportion of boron isotopes – a measurement that can serve as a proxy for ocean acidity – suggests that there is an increase in sea acidification 100 to 1000 years after exposure to the Chicxulub asteroid He told The Guardian that the walls of the fossilized shells also look "much thinner and badly calcified after impact."
In general, these clues suggest that the ocean pH has fallen by 0.25 units on the pH scale within the millennium since the asteroid collapses, (The scale starts from 0 for fully acidic and reaches 14 for completely alkaline; usually the ocean is alkaline.)
Although the millennium may seem like a long time, it means that the surface of the ocean is acidified on a "lightning" geological scale, according to the study's authors. This acidification has destroyed many plankton species, causing a global collapse of marine food chains and the latter Aloth mass extinction of ocean life.
"We are showing that ocean acidification can accelerate an ecological collapse," Henan added. "We had the idea before, but we didn't have the empirical evidence."
Acidification of the ocean today can cause such a severe collapse
According to the study's authors, this finding has implications for our understanding of the present state of our seas.
The oceans absorb 30% of the carbon dioxide emissions that humans emit. This causes chemical reactions in the water that acidifies the sea. Ocean pH has already dropped by 0.1 units – a 30% increase in acidity – since the start of the Industrial Revolution.
The drop in pH that occurred 66 million years ago was only 2.5 times less than the decrease we have seen in the last 250 years. According to the Smithsonian Institute, the pH of the ocean is expected to drop another 0.3 to 0.4 pH units by the end of the century.
"If 0.25 was enough to precipitate mass extinction, we have to worry," Henehan said.
Acidification of the ocean is faster than at any point in the last 300 million years, according to a 2012 study by Planavsky told the New York Times that this rate could be comparable to the lightning acidification that followed the asteroid killing dinosaurs.
Mass extinction like this "is at the extreme of what we might get in the next 100 years," he said.