\n Media contact:<\/strong> Brittany Steff, bsteff@purdue.edu<\/a> <\/p>\n <\/div>\n Note to journalists:<\/p>\n \n A video link<\/a> is available to media who have an Associated Press subscription, or on Google Drive<\/a>. Photos are available here<\/a>. <\/p>\n <\/div>\n <\/div>\n <\/div>\n<\/div>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" WEST LAFAYETTE, Ind. \u2014 Sixty-six million years ago, an asteroid about the size of Mount Everest smacked into Earth near where the Yucatan Peninsula is today. That impact created the Chicxulub crater and may have knocked out about three-quarters of<\/p>\n","protected":false},"author":25,"featured_media":22559,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[7],"tags":[],"department":[],"source":[29],"purdue_today_topic":[],"coauthors":[77],"class_list":["post-22560","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research-excellence","source-purdue-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/posts\/22560","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/users\/25"}],"replies":[{"embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/comments?post=22560"}],"version-history":[{"count":6,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/posts\/22560\/revisions"}],"predecessor-version":[{"id":22583,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/posts\/22560\/revisions\/22583"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/media\/22559"}],"wp:attachment":[{"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/media?parent=22560"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/categories?post=22560"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/tags?post=22560"},{"taxonomy":"department","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/department?post=22560"},{"taxonomy":"source","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/source?post=22560"},{"taxonomy":"purdue_today_topic","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/purdue_today_topic?post=22560"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.purdue.edu\/newsroom\/wp-json\/wp\/v2\/coauthors?post=22560"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
Brandon Johnson<\/a>, the study\u2019s lead author, is an expert in craters and impacts<\/a>. He studies how planetary bodies impact \u2014 literally \u2014 other planetary bodies, including the Chicxulub impact<\/a> that many scientists believe triggered the extinction of the dinosaurs along with much of the planet\u2019s other life.<\/p>\n\n\n\n A professor in the Department of Earth, Atmospheric, and Planetary Sciences<\/a> at Purdue, Johnson studies the physics of planetary collisions to pin down exactly what happened and how: a forensic crash investigator 66 million years after the fact.<\/p>\n\n\n\n \u201cThat much kinetic energy has to go somewhere and eventually it is converted to heat,\u201d he said. \u201cWith the dust cloud trapping thermal radiation, it was like the surface and everything on it was being charbroiled. And that\u2019s what killed the dinosaurs and all the other animals. It\u2019s not the blast wave from the impact or the fireball \u2014 those don\u2019t go very far. It\u2019s the global ejection of this vapor plume material that makes this a global extinction event. Without the dust cloud, it would have been bad. It would have killed a lot of creatures. But it wouldn\u2019t have been a planetary catastrophe.\u201d<\/p>\n\n\n\n In previous research with Jay Melosh, Johnson\u2019s advisor and former collaborator at Purdue, Johnson discovered<\/a> that when the Chicxulub asteroid hit, it vaporized over 1,000 cubic kilometers of material \u2014 largely rock and dirt, though also whatever animals and plants were in the way.<\/p>\n\n\n\n All that material expanded in a plume above the atmosphere. As the vapor rose into the air, it cooled and then condensed, just as water vapor does. But instead of condensing into raindrops, the impact vapor condensed into droplets of rock, dubbed spherules. The spherules are relatively large as tiny specks go \u2014 about 250 micrometers in diameter, or about half the size of a grain of sugar.<\/p>\n\n\n\n As the spherules fell back to Earth, the resistance of the surrounding air heated them up and turned them into miniature versions of the asteroid impact itself. That additional heat added to what was generated in the initial impact.<\/p>\n\n\n\n Paleontologists have uncovered spherules from all over the world, including from the gills of paddlefish at a site in North Dakota who likely died on the day the asteroid hit. Previous research had found that the spherules were made up of material of terrestrial origin \u2014 nothing from the asteroid itself. That material, it turns out, did not precipitate into spherules but instead became a cloud of fine dust that ballooned across the entire planet. That asteroid dust later insulated the planet like a smothering blanket that wouldn\u2019t allow heat to escape.<\/p>\n\n\n\n The dust cloud changed the impact from merely tragic to apocalyptic.<\/p>\n\n\n\n \u201cWith this fine dust cloud capping the atmosphere, the heat radiation can\u2019t escape to space,\u201d Johnson said. \u201cSo the only place that radiation can go is back down to the earth. Without fine dust, this still wouldn\u2019t have been a good day for dinosaurs. It would have killed some off, but it probably wasn\u2019t enough to start many wildfires. With the fine dust, the Cretaceous animals received 17 times the dose of thermal radiation that is 100% lethal to humans. It was enough to ignite grass, pine needles, lichen and maybe even directly ignite wood.\u201d<\/p>\n\n\n\n With the blanketing clouds and boiling heat, Johnson\u2019s description sounds like the surface of Venus. But the comparison, he says, is not quite apt.<\/p>\n\n\n\n \u201cIt probably looked more like hell than like Venus,\u201d he said. \u201cThe clouds would have blocked daylight so to any animal, like humans, that don\u2019t see far into the infrared, the surface would have probably looked dark. You would only have been able to see a reddish glow from the wildfires. But there really wouldn\u2019t be anything alive to do the seeing anyway, except for any animal that was able to burrow or swim or shelter in some way, to find a way to survive. It would have been terrible.\u201d<\/p>\n\n\n\n To analyze how well the dust cloud would have insulated the planet, the team brought in Alexandria Johnson<\/a>, an expert on clouds.<\/p>\n\n\n\nThe sky is falling<\/h2>\n\n\n\n
![\"Two](\"https:\/\/www.purdue.edu\/newsroom\/wp-content\/uploads\/2026\/07\/johnsons-portrait.jpg\" "\\"\\"")
Ashes to ashes, dust to dust<\/h2>\n\n\n\n