Dinosaurs May Have Been Incinerated By Heat Trapped By Dust From Asteroid Strike

Science News reports on a new study that suggests that after the Chicxulub asteroid struck the Earth, creating a 200-km wide crater, the land dwelling dinosaurs not killed immediately from the impact would have been incinerated by heat trapped under the dust kicked up into the atmosphere. 

    When the asteroid hit, it vaporized the surrounding rock, creating the 200-kilometer-wide Chicxulub crater underneath the Gulf of Mexico. Some of the vapor cooled in the atmosphere and condensed into droplets of molten rock. The rest became a cloud of fine dust.

    What happened next has been a long-standing question, says planetary scientist Brandon Johnson of Purdue University in Lafayette, Indiana. Using deposits of asteroid material from North Dakota, Johnson and his collaborators simulated what would have happened as this dust spread around the globe.

    The results painted a frightening picture. Molten rock would have rained down with the force of a bullet, generating a lot of heat. Instead of escaping into space, that heat would have been trapped by the dust cloud and radiated back to Earth’s surface. The air would have warmed rapidly, turning the sky red, while any creature that couldn’t take shelter received 17 times the lethal dose of thermal radiation for humans. About an hour later, the radiation would have dissipated, and the dust cloud would have blocked out the sun. The only light would have been from global wildfires spontaneously ignited by the heat.    

And, per this article from the Guardian, the Chicxulub asteroid may not have been a one-off:

    Detailed scans of an underwater crater off the coast of Guinea in West Africa suggest that it was created when another large asteroid smashed into the planet around the same time at the end of the Cretaceous period.

    The violent impact between 65m and 67m years ago produced a crater more than five miles across, the scans reveal, with scientists estimating that the asteroid measured a quarter of a mile wide and struck Earth at nearly 45,000mph.

    Though smaller than the asteroid that sparked the mass extinction, it was still large enough to leave scars on the face of the planet. “The new images paint a picture of the catastrophic event,” said Dr Uisdean Nicholson, a marine geologist at Heriot-Watt University in Edinburgh, who first discovered the Nadir crater in 2022. At the time, the details of the impact were unclear. 

[snip] 

    The researchers cannot pinpoint when the asteroid struck Earth, but the discovery of the crater and its approximate age have prompted speculation that it may have belonged to a cluster of impacts at the end of the Cretaceous period. The asteroid linked to the extinction of the dinosaurs was far larger than the rock that produced the Nadir crater. It left a crater 100 miles wide in what is now Chicxulub on the Yucatan peninsula in Mexico.