About 66 million years ago, our beautiful planet suffered a veritable cataclysm that took dinosaur life with it. With a diameter of more than 10 kilometers, this asteroid left a slim chance of survival for living creatures, leading to the extinction of 75% of them. The only survivor of this apocalyptic event: the Earth. Solid as a rock, this blue planet!
But then, is she immune to the Armageddon of asteroids? What would be the span of the rock capable of ending its existence? According to Space.com, the answer is obvious: to destroy the Earth, you would undoubtedly need a celestial body as imposing as… the Earth.
It would seem that our planet has not gone very far during its existence. “An object larger than Mars hit our planet, without destroying it, and created the Moon”, says Brian Toon, professor of atmospheric and oceanic sciences at the University of Colorado at Boulder. He is a fervent defender of the giant impact hypothesis, the scientific theory according to which the Moon was the result of the collision between the planet Theia and the Earth 4.468 billion years ago, during which part of Theia’s core and mantle would have fused with that of Earth.
Human life hangs by a thread of 140 meters
If our planet is much more robust than we think, it is not the same for humans. As the extinction of the non-avian dinosaurs shows, it takes much less than a rebellious celestial body to seriously disrupt life on Earth. “A collision with a rock at least a kilometer wide would likely trigger the end of civilization” by generating global climatic catastrophes, tells the Scientific American journal Gerrit L. Verschuur, an astrophysicist at Rhodes College in Memphis.
“The dust from the impact and the smoke from the fires [produits par la collision] would girdle the Earth, plunging it into a winter of impact [phénomène caractérisé par une baisse significative de température globale de la Terre due à la collision avec un corps extraterrestre, ndlr]. Thus, the sky would be obscured by the harmful gases and the plants could no longer carry out photosynthesis. The end of plant and animal life follows. Only very small animals would have a chance of surviving.”continues the astrophysicist.
For NASA, any space rock measuring at least 140 meters in diameter and orbiting within 7.4 million kilometers of our planet is a danger. Such a collision could wipe out an entire city and, moreover, devastate the surrounding lands. It is therefore understandable that the federal agency takes the thousands of potential impactors very seriously.
But if an asteroid were to unexpectedly change course and take Earth as its target, the success of the DART mission, led by NASA, reassures us: an assault by a spacecraft can be a viable means of planetary defense.
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