It’s a cataclysm that has caused a lot of ink to flow among researchers, a real scientific saga. It wasn’t just an asteroid that killed the dinosaurs 66 million years ago. We are talking again this week about asteroids, with Mathilde Fontez, editor-in-chief of the scientific magazine Epsiloon. We followed last week NASA’s test, which sent a probe to deflect an asteroid into space, to test our ability to protect ourselves from dangerous impacts.
franceinfo: 66 million years ago, it was not one but two asteroids that caused the extinction of the dinosaurs.
Mathilde Fontez: Yes, it’s a long-term scientific quest, this disappearance of the dinosaurs. Disappearance of dinosaurs and 70% of species that were present on Earth! This is what gave space to one group in particular to develop: mammals and humans. Maybe we wouldn’t be here if the dinosaurs hadn’t gone extinct.
And to explain this brutal extinction, researchers have long thought of two options, volcanism or an asteroid fall. And then a huge 180 kilometer crater was discovered in Mexico, the Chicxulub crater, in the 80s, proof that a 10 kilometer asteroid hit the Earth.
But that’s not the end of the story…
Indeed, the story rebounds today, because researchers have discovered another crater, which dates from exactly the same time. You had to find it, it is located in the ocean, off Guinea, in West Africa, 900 meters deep. And it is buried under a layer of 300 meters of sediment.
It was the study of the reflections of seismic waves in the layers of the Earth that made it possible to reveal this. It’s 8.5 kilometers in diameter, and it has all the characteristics of an asteroid impact crater: a raised rim; a terraced crater floor; a central uprising. In short, there is no doubt, it is the result of a shock with a body from space, at least 400 meters in diameter.
So it was two asteroids that caused the extinction of the dinosaurs?
Yes. In any case, this Nadir crater – that’s what the researchers called it – and the Chicxulub crater seem to be linked. Or it’s a double asteroid that suddenly headed for Earth. Or it’s a very large asteroid that split up and rained down on Earth. Because there are also other craters that seem to date from the same time that have been found – in Ukraine, in Poland. Their date is not certain, it does not allow to conclude. But she seems to stick. And there are also impacts on the Moon.
That asteroid shower hit the moon?
It is a possibility, yes. It is the analysis of the Moon samples brought back by the Chinese mission Chang’e-5, in 2020, which shows it: it has made it possible to refine the dating of the lunar craters. And to show that there is a whole group whose age revolves around the famous 66 million years.
So it was a huge cataclysm that took place at that time?
Yes, and one can imagine it. The simulations carried out by the researchers from the dimensions of the Nadir crater give an overview: an energy released of 5000 megatons of TNT; a 5 kilometer fireball immediately after impact; a blast of air at almost 500 km/h; a planetary earthquake of magnitude 7; a curtain of dust 2 kilometers high. Just this shock, much smaller than that of Chicxulub, had a planetary impact…