Some 65 million years ago, the strongest impact of asteroids over a billion years could have sown life throughout the solar system, even if it ravaged life. on earth. Projected debris escaped the gravitational force of the Earth by forming irregular orbits around the sun, eventually making its way to the planets and moons of the solar system. Mars was finally covered with debris and, according to a study carried out in 2013 in the newspaper astrobiology, the 14 km wide object projected tens of thousands of pounds of rubble that would have landed on Titan, the moon of Saturn, and Europa and Callisto, which revolve around Jupiter – all satellites that, according to scientists , are home to promising habitats for life. Mathematical models indicate that at least some of these debris still carried live microbes.
"If some evening, about sixty-six million years ago, you were somewhere in North America and looking at the sky, you would soon have discovered what seemed like a star," writes Douglas Preston in The Day the Dinosaurs. Both dead. "If you had been watching for an hour or two, the star would have seemed to get brighter and brighter, although it had barely moved. That's because it was not a star, but an asteroid and it was heading straight for the Earth at about 45,000 kilometers an hour. Sixty hours later, the asteroid was hit. "
"The day the earth rained glass" – Relation to extinction
The air at the front was compressed and violently heated as the object dug a hole in the atmosphere, generating a supersonic shock wave and vaporizing on impact, mingling with the vaporized terrestrial rock. forming a fiery plume collapse into a pillar of incandescent dust. The asteroid struck a shallow sea where today lies the Yucatán Peninsula, ending the Cretaceous at the dawn of the Paleogene, thus creating the pathway for the emergence of the # 39; human species.
"The asteroid itself was so big that even at the moment of impact, the summit could have exceeded even more than one kilometer at the cruise altitude of one. 747 ", writes Peter Brannen in Ends of the World. "In his almost instantaneous descent, he compressed the air below him so violently that he briefly became several times hotter than the surface of the sun", hitting the Earth with enough force to bring back a mountain in space at the exit speed.
A few years ago, Preston reports, scientists at Los Alamos National Laboratory used what was at the time one of the most powerful computers in the world, the so-called Q Machine, to model the effects of the impact, creating a slow motion second video in fake color of the event:
"Less than two minutes after hitting the Earth, the asteroid, which was at least six miles wide, had dug a crater to a depth of about 18 miles and thrown 25,000 billion tons of debris into the atmosphere. . Imagine the splash of a pebble falling into the water of a pond, but on a planetary scale. When the Earth's crust rebounded, a peak above Mt. Everest has briefly risen. The energy released exceeded that of one billion bombs from Hiroshima, but the explosion was nothing like a nuclear explosion, with its characteristic mushroom cloud. Instead, the first eruption formed a "cock tail," a gigantic stream of molten material, which left the atmosphere, part of which faded into North America. Much of the matter was several times warmer than the surface of the sun and burned all within a thousand kilometers. In addition, an inverted cone of liquefied and overheated rock rose, extending outward in the form of innumerable pieces of red-hot glass, called tektites, and overlying the surface. 39, Western Hemisphere.
The problem of three meters
Scientists are still debating many details derived from computer models, field studies on the debris layer, knowledge about extinction rates, fossils and microfossils, and many other clues, Preston writes. , sinister. Dust and soot resulting from impact and fires prevented all sunlight from reaching the surface of the planet for months. Photosynthesis has virtually ceased, killing most of the plant life, extinguishing phytoplankton in the oceans and causing the drop of oxygen in the atmosphere. After the end of the fires, the Earth sank in a period of cold, even freezing. The two essential food chains of the Earth, at sea and on land, have collapsed. About 75% of all species have disappeared. More than 99.9999% of all living organisms on Earth are dead and the carbon cycle has stopped. "
The earth itself has become toxic because of the impact, vaporizing layers of limestone and releasing powerful greenhouse gases into the atmosphere: one trillion tons of carbon dioxide, ten billion tons of methane and one billion tons of carbon monoxide. The impact also vaporized anhydrite rock, inflating 10,000 billion tons of sulfur compounds. by combining with water to form sulfuric acid, which then fell in the form of an acid rain.
One of the mysteries of paleontology is the "three-meter problem": in a century and a half of diligent research, almost no remains of dinosaurs were found in the three-meter layers, about three meters under the KT . border that marks the dividing line between the Cretaceous and the Tertiary. (The Tertiary has been redefined as the Paleogene) a depth representing several thousand years. As a result, reports Preston, many paleontologists have claimed that the dinosaurs were about to disappear long before the asteroid hit, possibly due to volcanic eruptions and climate change. Other scientists have argued that the three-meter problem only reflected the difficulty of finding fossils. Sooner or later, they said, a scientist will discover dinosaurs much closer to the time of destruction.
The answers to our questions about one of the most significant events in the history of life on the planet are buried in the KT limit. If we consider the Earth as a living organism, as many biologists do, Preston writes, we can say that she was hit by a bullet and almost died. Deciphering what happened on the day of destruction is crucial not only to solving the three-meter problem, but also to explaining our own genesis as a species.
Enter a Robert DePalma: In March 2019, The Galaxy published the message "The day the earth had rained glass" – Statement of extinction describing the horror of the impact. The beginning of the end began with violent shocks that raised giant waves in the waters of an inland sea of North Dakota. Then, tiny glass beads began to fall like a bird's eye from the sky. The rain of glass was so strong that it may have set fire to much of the earth's vegetation. According to paleontologist Robert DePalma, the fish was struggling to breathe when the pearls clogged their gills, about the field of death established soon after the impact of the asteroid that eventually led to the Extinction of all terrestrial dinosaurs at the end of the Cretaceous period. the so-called KT limit, which has exterminated 75% of life.
"This is the first large-body assemblage of mass death associated with the K-T boundary," said DePalma, paleontology curator at the Palm Beach Museum of Natural History. "In no other section of the KT boundary on Earth, you will find such a collection including a large number of species representing different ages of organisms and different stages of life, all of which are dead at the same time, the same day."
The discovery of DePalma was in the Hell Creek geological formation, which was found in parts of North Dakota, South Dakota, Montana and Wyoming, among the world's most famous dinosaur beds. At the time of impact, the Hell Creek landscape consisted of subtropical and wet lowlands and subtropical floodplains along the shores of an inland sea. The land was full of life and conditions were excellent for fossilization, with seasonal floods and winding rivers that quickly buried plants and dead animals.
DePalma christened the Tanis site, named after the ancient city of Egypt, which appeared in the 1981 film "The Lost Ark Adventurers" as the resting place of the arch of the alliance. In the real Tanis, archaeologists have found an inscription in three writing systems that, like the Rosetta Stone, was crucial for the translation of the ancient Egyptian.
A cosmic impact powerful enough to annihilate all life on the surface of the Earth would put large quantities of rocks in orbit around the sun. Steinn Sigurðsson, a professor in the astronomy and astrophysics department at Penn State University, said Steinn Sigurðsson, "which is particularly reassuring," said Steinn Sigurðsson. Sigurðsson said last month at the Breakthrough Talk conference at the University of California at Berkeley.
"Space Refugees" – An impact on the extinction of dinosaurs: an ejecta would revive life
"If you have a sterilizing impact – if you have a killer beyond the dinosaurs, something that will fry the entire planet," there is a significant likelihood that biota will be ejected and come back to the planet, hopefully gently , quickly enough, to reseed quickly. planet. "The existence of such" spatial refuges "is supported by computer simulations Sigurðsson and his colleagues who followed the trajectories of rocks projected out of the Earth and other rocky planets orbiting the Earth. Sun.
During the hundred million years of their existence, before the asteroid struck, mammals rushed under dinosaurs' feet. "But when the dinosaurs disappeared, he released them," DePalma said. In the near future, mammals experienced an explosion of adaptive radiation observed by Preston, evolving into a dazzling variety of forms, ranging from tiny bats to gigantic titanotheres, horses to whales, fearsome creodonts to big-brained primates with skilled hands. it could see through time.
"We can trace our origins to this event," said DePalma. "To be really on this site, to see it, to be connected to this day, is a special thing. It's the last day of the Cretaceous. The next day, when you go to bed, it's the Paleocene, it's the age of mammals, it's our age.
The Daily Galaxy via the New Yorker, University of California – Berkeley, Peter Brannen.com
In text image, The day the dinosaurs died, thanks to BBC Bancroft