[ad_1]
Asteroid dust located in the Chicxulub crater has been interpreted as the definitive proof that a cataclysm of this nature wiped out the dinosaurs 66 million years ago.
Death by asteroid rather than a series of volcanic eruptions or some other global calamity has been the leading hypothesis since the 1980s, when scientists found asteroid dust in the geological layer that marks the extinction of the dinosaurs. This discovery painted an apocalyptic picture of vaporized asteroid dust and impact rocks surrounding the planet, blocking the sun and causing massive death through a dark and sustained global winter, before settling to the ground.
In the 1990s, the connection was strengthened with the discovery of the 200-kilometer-wide Chicxulub impact crater beneath the Gulf of Mexico that is the same age as the rock layer. A new study clears the doubts, according to its authors, by finding asteroid dust with a similar chemical footprint inside that crater at the precise geological location that marks the moment of extinction.
“The circle is now finally complete”Steven Goderis, professor of geochemistry at Vrije Universiteit Brussel, who led the study published in Science Advances, said in a statement.
The study is the latest in a 2016 International Ocean Discovery Program mission co-led by the University of Texas at Austin that collected nearly 1,000 meters of rock core from the crater buried under the seafloor. Investigating this mission has helped fill the gaps in impact, aftermath, and recovery of life.
The telltale sign of asteroid dust is the element iridium, which is rare in the Earth’s crust, but is present at high levels in certain types of asteroids. An iridium spike in the geological layer found all over the world is how the asteroid hypothesis was born. In the new study, the researchers found a similar peak in a section of rock removed from the crater. In the crater, the layer of sediment deposited in the days or years after the impact is so thick that scientists were able to accurately date the dust as little as two decades after the impact.
“We are now at the level of agreement that geologically it does not happen without causation,” said co-author Sean Gulick, a research professor at the UT Jackson School of Geosciences who co-led the 2016 expedition with Joanna Morgan of Imperial College London. Eliminate any doubt that the iridium anomaly [en la capa geológica] it is not related to the Chicxulub crater ”.
The dust is all that remains of the 10-kilometer-wide asteroid that crashed into the planet millions of years ago, causing the extinction of 75% of life on Earth, including all non-avian dinosaurs.
The researchers estimate that the dust raised by the impact circulated in the atmosphere for no more than a couple of decades, which, Gulick says, helps estimate how long the extinction took.
“If you’re really going to set a clock to extinction 66 million years ago, you could easily argue that it all happened in a couple of decades, which is basically the time it takes for everything to starve to death.”, He said.
The highest concentrations of iridium were found within a 5-centimeter section of rock core recovered from the top of the crater’s peak ring, a point of high elevation in the crater that was formed when rocks rebounded and then collapsed by the force of impact.
Iridium analysis was carried out in laboratories in Austria, Belgium, Japan, and the United States. “We combined the results from four independent labs around the world to make sure we got it right,” Goderis said.
In addition to iridium, the crater section showed elevated levels of other elements associated with the asteroid material. The concentration and composition of these “asteroid elements” resembled measurements taken from the geological layer at 52 sites around the world.
The core section and the geologic layer also have terrestrial elements in common, including sulfur compounds. A 2019 study found that sulfur-containing rocks are largely missing from the rest of the core despite being present in large volumes in the surrounding limestone. This indicates that the impact blew the original sulfur into the atmosphere, where it may have made a bad situation worse by exacerbating global cooling and seeding acid rain.
[ad_2]
