“Don’t Look Up”: What would happen if a comet really hit Earth?

Many feature films have had fun imagining what could happen to Earth and its inhabitants if a asteroid or a comet came crashing into the Planet. The general public was able to savor the outrageous heroism of Bruce Willis in Armageddon or the disproportionate special effects of a Deep Impact. The film Don’t Look Up, released on Netflix December 24, 2021, starts from a similar postulate: two astronomers, played by Jennifer Lawrence and Leonardo DiCaprio, discover a comet heading towards Earth. Scientists quickly find themselves confronted with media disinterest and government inaction as the Earth prepares to be destroyed. But the film’s script, which takes on an aura of seriousness in its treatment of the cosmic threat, is it credible?

A big story

In Don’t Look Up, doctoral student Kate Dibiasky discovers a comet about 10 kilometers wide, realizing a few hours later that it threatens the Earth, on which it will crash six months later. The comet, designated by scientists as a “planet killer”, reached the Pacific Ocean, causing an unprecedented cataclysm and the almost immediate extinction of animal and plant life.

In space, there are indeed different types of bodies and celestial objects that can be a threat. The Center for the Study of Near-Earth Objects Nasa (Center for Near Earth Objects Studies), in charge of monitoring objects and asteroids gravitating in a perimeter relatively close to the Earth, has identified nearly 27,000 asteroids.

Only 2,000 of them are considered potentially dangerous, and 158 are equal to or greater than one kilometer in diameter. Among these asteroids, some have acquired a great reputation among the followers of apocalyptic theories. Apophis and its 350 meters in diameter and the most imposing Bénou, measuring 500 meters in diameter, come back annually in the end of the world predictions.

Some comets can have sizes similar to the more massive asteroids, only their compositions make it possible to differentiate the two types of celestial objects. However, some comets reach disproportionate dimensions, sometimes much more impressive than comet Dibiasky from Don’t Look Up. C / 2014 A₂₇₁, Where Bernardinelli-Bernstein, imaged for the first time in 2014, could thus have a diameter of nearly 100 kilometers. By way of comparison, the diameter of Bernardinelli-Bernstein would include that of Ile-de-France!

“Planet killers”?

Can we seriously consider that such objects destroy the Planet and all life on its surface? One simulator, created by researchers fromImperial College of London and Purdue University, shows that an object 10 kilometers in diameter crashing at 51 meters per second on Earth would cause considerable material damage. The impact of such a comet in the center of Paris would calcine the majority of soil over the entire French territory, burning in the third degree an observer located more than 700 kilometers away, while in Toulouse, the theoretical maximum force of the blast would be 725 meters per second. At the point of impact, everything would be obliterated in a sector 300 kilometers in diameter, with a earthquake of a magnitude of 10.4 onRichter scale.

David Morrison, astronomer working for theAmes Research Center of NASA, explained in 1999 to the magazine Scientific American that the impact of a massive body of 10 kilometers, with a power of 100 million megatons, could cause a mass extinction. In addition to the violence of the impact and the immediate effects mentioned above, the collision would release a vast mass of dust and matter which would permanently obscure theatmosphere earthly. It was a similar event that accelerated the disappearance of dinosaurs, 66 million years ago.

But, for now, no comet or asteroid threatens Earth directly. NASA and other space agencies keep the planet safe with tools such as the Sentry program. Programs to deflect objects grazing the Earth are under study. In November 2021, NASA launched the Dart mission which will test the deflection capabilities of an asteroid using a probe in September 2022.