Mark A. Garlic
An artist’s impression of the impact of the asteroid that created the Chicxulub crater off the coast of what is now Mexico. Within weeks or months after the strike, the dust had blocked out the sun, halting photosynthesis.
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The age of the dinosaurs ended 66 million years ago when a city-sized asteroid crashed into a shallow sea off the coast of what is now Mexico.
But how the mass extinction of about 75% of Earth’s species occurred in the years following the catastrophic impact remains unclear.
Previous research has suggested that sulfur released during the impact, which left the 112-mile-wide (180-kilometer) Chicxulub crater, and soot from wildfires caused a global winter and lower temperatures.
However, A A new study published Monday in the journal Nature Geoscience suggests that fine dust made from crushed rocks thrown into Earth’s atmosphere following the impact likely played a larger role. This dust obscured the sun to such an extent that plants were unable to carry out photosynthesis, a biological process critical to life, for about two years afterward.
“The cessation of photosynthesis for approximately two years after the impact caused severe challenges (for life),” said lead study author and planetary scientist Jim Burke Senel, a postdoctoral researcher at the Royal Observatory of Belgium. “The food web collapsed, setting off a chain reaction of extinction.”
A pink-brown layer in sediment from a site in North Dakota contains material ejected from Chicxulub crater that was used as part of a climate modeling study.
To arrive at their findings, the scientists developed a new computer model to simulate the global climate after the asteroid strike. The model relied on published information about the Earth’s climate at the time, in addition to new data from sediment samples taken from the Earth. Tanis fossil site in North Dakota Which captured the 20-year period following the strike.
The Tanis fossil site provides a unique record of what was perhaps the most important event in the history of life on our planet. Fossilized fish found at the site revealed that the asteroid had struck Off Mexico’s Yucatan Peninsula in spring. Other excavations Found there showing how the disastrous day unfolded In unprecedented detail.
The sample taken from the site, which was analyzed for the new study, contained silicate dust particles that had been propelled into the atmosphere in an ejecta plume before returning to Earth.
The team determined that this fine dust could have remained in the atmosphere for up to 15 years after the asteroid impact. The researchers indicated that the global climate may have decreased by up to 15 degrees Celsius.
Their research represents the first time these dust particles have been studied in detail.
“It has long been assumed that the main killing mechanism was extreme cold after the Chicxulub impact, but of course the cessation of photosynthesis after the impact is the mechanism itself,” Senel said.
“Within a few weeks or months (of the impact), the planet experienced a global cessation of photosynthesis, which lasted for approximately two years during which photosynthesis completely disappeared,” Senel added. “Then it starts to go back into recovery after those two years. …And within three to four years, it reaches full recovery.”
A Helos laser diffraction grain size analyzer was used to measure the properties of dust present in sediment samples.
The model revealed that the cessation of photosynthesis — the process in which plants use sunlight, water and carbon dioxide to produce energy and oxygen — is directly linked to fine dust emitted into the atmosphere that blocks the sun, Senel said.
Paleontologist Alfio Alessandro Chiarenza said the study helped uncover some of the mysteries surrounding the mass extinction event.
“The main takeaway from this paper is that it provides more precise constraints on the composition, properties and duration of the fine dust component emitted from the impact site, which contributed to the global darkness during the impact winter,” said Chiarenza, a postdoctoral researcher. Research fellow at the University of Vigo in Spain. He did not participate in the study.
“This new information enables us to investigate the processes and duration more precisely, and shed light on the mechanisms behind the blockage of solar radiation, which leads to the cessation of photosynthesis and a significant drop in temperatures below habitable conditions for example for non-avian dinosaurs.” . Chiarenza added.
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