Although there are still some dissenters, the scientific consensus is the dinosaurs died as the direct result of an asteroid hitting our planet.
Exactly how would that event have unfolded? I’ve recently found an article on The New Yorker website that discusses the sequence of events in great detail. And according to the best scientific information, we almost lost our planet that day.
Thanks to some sophisticated modeling by scientists at Los Alamos National Laboratory a few years ago, scientists have a good idea of what must have happened. To quote —
“Within two minutes of slamming into Earth, the asteroid, which was at least six miles wide, had gouged a crater about eighteen miles deep and lofted twenty-five trillion metric tons of debris into the atmosphere…. When Earth’s crust rebounded, a peak higher than Mt. Everest briefly rose up. The energy released was more than that of a billion Hiroshima bombs, but the blast looked nothing like a nuclear explosion…. Instead, the initial blowout formed a “rooster tail,” a gigantic jet of molten material, which exited the atmosphere, some of it fanning out over North America. Much of the material was several times hotter than the surface of the sun, and it set fire to everything within a thousand miles. In addition, an inverted cone of liquefied, superheated rock rose, spread outward as countless red-hot blobs of glass, called tektites, and blanketed the Western Hemisphere.”
One result I hadn’t considered was the effect the asteroid strike had on the rest of the solar system —
“Some of the ejecta escaped Earth’s gravitational pull and went into irregular orbits around the sun. Over millions of years, bits of it found their way to other planets and moons in the solar system. Mars was eventually strewn with the debris—just as pieces of Mars, knocked aloft by ancient asteroid impacts, have been found on Earth. A 2013 study in the journal Astrobiology estimated that tens of thousands of pounds of impact rubble may have landed on Titan, a moon of Saturn, and on Europa and Callisto, which orbit Jupiter—three satellites that scientists believe may have promising habitats for life. Mathematical models indicate that at least some of this vagabond debris still harbored living microbes. The asteroid may have sown life throughout the solar system, even as it ravaged life on Earth.”
Ravaged is a good description. There were wide-spread forest fires and giant tsunamis. So much dust and soot was in the atmosphere that sunlight couldn’t reach Earth, leading to an end of photosynthesis and a period of cold, perhaps extreme cold. The impact vaporized limestone, releasing an estimated trillion tons of carbon dioxide, plus huge quantities of methane, carbon monoxide, and sulfur compounds, some of which combined with water to form sulfuric acid.
In other words, Earth itself became toxic; an estimated seventy-five per cent of all species went extinct and more than 99.9999 per cent of all living organisms died. Earth came very close to being a dead planet.
If after this grim scenario, you’re still curious about the scientific legwork that is validating this sequence of events, this fascinating and extensive article is “The Day the Dinosaurs Died” by Douglas Preston at https://www.newyorker.com/magazine/2019/04/08/the-day-the-dinosaurs-died?