For starters, it’s circular in shape, with a pronounced rim. The putative crater is buried under roughly 300 meters of sediments topped by 900 meters of water, and its appearance strongly suggests it was created by a hypervelocity impact, said Nicholson. “There’s a lot of things that suggest it’s an impact.” “It was pure serendipity,” said Nicholson. The team spotted the roughly 8-kilometer-wide structure in seismic reflection imaging data obtained off the coast of West Africa. Uisdean Nicholson, a sedimentary geologist at Heriot-Watt University in Edinburgh, Scotland, and his colleagues discovered the candidate crater while they were poring over observations of seafloor sediments originally collected for oil and gas exploration. The newly discovered Nadir crater appears to have formed right around the same time as that cataclysm. When the air finally cleared, over 75% of all species had gone extinct. And airborne particles-bits of dust, soot, and sulfate aerosols born from the sulfur-rich rocks that existed at the Chicxulub impact site-choked the atmosphere and plunged the entire planet into a sunlight-starved “impact winter” that lasted for years. That event, now known as Chicxulub after the small town that’s grown up nearby in Mexico, launched shock waves, powerful tsunamis, and blasts of superheated air that decimated life in the vicinity. That’s what happened 66 million years ago when a roughly 12-kilometer-wide asteroid slammed into a shallow reef in the Gulf of Mexico. That microscopic debris poses no danger to life on Earth, but its larger brethren are very much cause for concern: A space rock measuring hundreds of meters in size is apt to cause regional destruction, and the arrival of something measuring kilometers in size could spell global havoc. Every day, tons of cosmic dust rain down on our planet.
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