The author is an astronomer, science communicator and professor of science education at UQAM.
Earlier this week, NASA announced the first results of the DART experiment (Double Asteroid Redirect Test), which consisted of hitting an asteroid with the help of a space probe in order to check whether it was possible to deviate its trajectory significantly. According to the most recent observations of the asteroid Dimorphos, which was the target of the experiment, the collision succeeded in modifying its trajectory well beyond the expectations of those responsible for the mission, which bodes well for the future.
What the DART mission achieved is the equivalent in billiards of hitting a moving colored ball with the cue ball, except here the balls were moving tens of thousands of miles away. hour and were more than eleven million kilometers from Earth at the time of impact! This is a real feat that dramatically demonstrates that humanity now has the means to protect itself if an asteroid or a comet (small, let’s be real) hurtles towards Earth and we become aware of it enough in advance.
The solar system is a dangerous place where a multitude of objects of all sizes, asteroids, comets and meteoroids, revolve around the Sun in more or less stable orbits, at the mercy of the slightest disturbance which could launch them towards the Earth. Fortunately, a battery of automated telescopes scans the sky night after night to detect them and calculate their future positions.
So far, more than 20,000 of these objects have been detected in orbits that occasionally cross that of the Earth; of these near-Earth stars, none currently constitute a threat, imminent or more distant in time, but we are not immune to a fortuitous discovery or even an asteroid or a comet hurtling towards us in the direction of the Sun, which would blind us, or whose trajectory would be modified to our detriment.
Either way, prevention is better than cure. Since the formation of the solar system 4.5 billion years ago, the Earth has experienced its share of devastating collisions. If it weren’t for the erosion that is slowly erasing the traces of this bombardment, the surface of our planet would resemble that of the Moon. There are still traces of the most recent collisions on Earth, such as the Manicouagan reservoir, formed 214 million years ago, and the Pingualuit crater, located in the far north of Quebec and barely 1.4 million years.
In the 1980s, geologists identified a large, 65 million year old impact crater off the Yucatan Peninsula, believed to be associated with the demise of the dinosaurs. According to the most probable scenario, an asteroid or a comet measuring ten kilometers in diameter (the size of Mount Everest, in short) would have descended on Earth off the coast of what is now Mexico, puncturing the Earth’s crust. and causing planet-wide chain earthquakes, tsunamis and volcanic eruptions.
The sky would have filled with soot that would have blocked sunlight from entering the atmosphere, stopping photosynthesis for decades or centuries, if not longer. It is the lack of food due to the collapse of the food chain and the general drop in temperatures that would have decimated more than 75% of the species living on Earth at that time, including the dinosaurs.
We owe our presence on Earth 65 million years later to small mammals, our ancestors, who at the time constituted a fairly marginal class of animals, but who survived this great catastrophe and who, once the dust settled (literally!), quickly occupied the many ecological niches left vacant by the large saurians. Unlike the dinosaurs, who were unable to develop technologies to guard against cosmic impacts, we now have a credible preventive measure, should this type of disaster occur again. Provided you survive the many other threats that currently weigh on humanity…