In the comments to yesterday’s post about climate change, a lot of people mentioned this article that appeared in The New Yorker and caused a big sensation.
I had already read the article and found it to be absorbing. It helps that the author of the piece is a novelist, because not only did the article zip right along, but it read almost like a short story, a very dramatic one. The picture it created of the aftereffects of the asteroid hit that is presumed to have ended the dominance of the dinosaurs as a group and paved the way for mammals to rise was both fascinating and terrifying:
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. Picture the splash of a pebble falling into pond water, but on a planetary scale. 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, with its signature mushroom cloud. 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.
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…
There’s much much more, but you get the idea.
The description of the discoverer of the fossil find that supposedly documents this event is fascinating as well. He appears to be monomaniacal about bones and how they fit together; obsessed with them from around the age of four, helped along by a great-uncle who was a renowned orthopedist.
“We have the whole KT event preserved in these sediments,” DePalma said. “With this deposit, we can chart what happened the day the Cretaceous died.” No paleontological site remotely like it had ever been found, and, if DePalma’s hypothesis proves correct, the scientific value of the site will be immense. When Walter Alvarez visited the dig last summer, he was astounded. “It is truly a magnificent site,” he wrote to me, adding that it’s “surely one of the best sites ever found for telling just what happened on the day of the impact.”
As I read the article, though, one thing that struck me was this question: hasn’t earth a lot of impact craters from fairly large asteroids? Did they cause similar extinctions? Was this the largest asteroid ever? The extent of the cataclysm described in the article is based on computer modelings, but how accurate are those modelings?
The following was in the article as well:
Scientists still debate many of the details, which are derived from the computer models, and from field studies of the debris layer, knowledge of extinction rates, fossils and microfossils, and many other clues. But the over-all view is consistently grim. The dust and soot from the impact and the conflagrations prevented all sunlight from reaching the planet’s surface for months. Photosynthesis all but stopped, killing most of the plant life, extinguishing the phytoplankton in the oceans, and causing the amount of oxygen in the atmosphere to plummet. After the fires died down, Earth plunged into a period of cold, perhaps even a deep freeze. Earth’s two essential food chains, in the sea and on land, collapsed. About seventy-five per cent of all species went extinct. More than 99.9999 per cent of all living organisms on Earth died, and the carbon cycle came to a halt.
Earth itself became toxic. When the asteroid struck, it vaporized layers of limestone, releasing into the atmosphere a trillion tons of carbon dioxide, ten billion tons of methane, and a billion tons of carbon monoxide; all three are powerful greenhouse gases. The impact also vaporized anhydrite rock, which blasted ten trillion tons of sulfur compounds aloft. The sulfur combined with water to form sulfuric acid, which then fell as an acid rain that may have been potent enough to strip the leaves from any surviving plants and to leach the nutrients from the soil.
So how did the mammals survive? What did they eat, for example? I’d like to know a lot more about that.
Would a similar-sized impact always and inevitably have a similarly horrific result? Haven’t many asteroids hit earth, and were some of them almost as big? I found this article that goes into the question a bit, enough for me to conclude that we aren’t entirely sure how big the Chicxulub crater (the impact described in the New Yorker article) actually is, although it’s certainly very very big. But I noticed that about five million years prior to Chicxulub, there had been another large impact (called the Kara crater) that doesn’t seem associated with any mass extinction (at least, I couldn’t find any discussion of it in a brief perusal). If not, then why?
I certainly don’t know. But I found an article from 2017 that raises some interesting points:
Of all the places in the world an asteroid could have walloped ancient Earth, the Yucatán Peninsula was possibly the worst…
According to the paper, this mass extinction happened because the space rock slammed into an oily tinderbox, blasting enough soot into the atmosphere to cause extreme global cooling…
The impact chilled the planet by a global average of 14 to 18 degrees Fahrenheit, with a drop of 18 to 29 degrees over land, the study finds.
Only 13 percent of Earth’s surface is made up of rocks that could have burned off that much soot, the team argues this week in Scientific Reports. That means if the asteroid had landed almost anywhere else, the nonavian dinosaurs may not have died out after all.
“This is a fascinating paper that … argues that even given the large size of the impactor, the mass extinction itself was of low probability,” says Paul Chodas, manager of the Center for Near Earth Object Studies at NASA’s Jet Propulsion Laboratory.
The possibility of a catastrophic asteroid impact is the meat-and-potatoes of many science fiction stories and films. Often they feature humankind attempting to head the asteroid off at the pass, and in real life we do have some rudimentary efforts to move in that direction:
In 2016 a NASA scientist warned that the Earth is unprepared for such an event. In April 2018, the B612 Foundation reported “It’s 100 per cent certain we’ll be hit [by a devastating asteroid], but we’re not 100 per cent sure when.” Also in 2018, physicist Stephen Hawking, in his final book Brief Answers to the Big Questions, considered an asteroid collision to be the biggest threat to the planet.[4][5][6] In March 2019, scientists reported that asteroids may be much more difficult to destroy than thought earlier. In addition, an asteroid may reassemble itself due to gravity after being disrupted.
If you’re interested in some of the contemplated approaches, see this. Suffice to say that our skills in this direction are in their infancy.
[NOTE: Here’s a database of known impact events.]