We will have to wait a few days to find out if the asteroid really deviated from its initial orbit.
The pictures are amazing. A NASA vehicle deliberately crashed into an asteroid on Monday to divert its path, during an unprecedented test mission that should allow humanity to learn how to protect itself from of a potential future threat.
The ship, smaller than a car, rushed at a speed of more than 20,000 km / h to its target, reaching the scheduled time (23:14 GMT). The Nasa teams, gathered at the mission control center in Maryland, United States, erupted in joy at the moment of the collision.
A few minutes before, the asteroid Dimorphos, located about 11 million kilometers from Earth, gradually grew in spectacular images broadcast live by the ship. We can clearly distinguish the pebbles on its gray surface, before the images stop at the moment of the explosion.
“We are entering a new era, where we have the possibility to protect ourselves from the dangerous impact of the asteroid,” said Lori Glaze, director of planetary sciences at NASA.
Dimorphos is about 160 meters in diameter and poses no danger to our planet. It is actually a satellite of a larger asteroid, Didymos, that it is far circumnavigated in 11 hours and 55 minutes. NASA aims to reduce the orbit of Dimorphos by 10 minutes, that is, bring it closer to Didymos.
It will take a few days to a few weeks before scientists can confirm that the asteroid’s path has indeed changed. They will do this thanks to telescopes on Earth, which will observe the difference in light as the small asteroid passes in front of and behind the large one.
If the goal remains moderate compared to the disaster scenarios of science fiction films such as ARMAGEDDON, this “planetary defense” mission, named Dart (dart, in English), was the first to test such a technique. This allows NASA to train in case an asteroid threatens to hit Earth one day.
“I think the Earthlings can sleep well, I do,” said Elena Adams, a mission engineer.
The ship has been traveling for ten months since it set sail in California. To hit a target as small as Dimorphos, the final flight phase is fully automatic, like a self-guided missile.
Three minutes after the impact, a shoebox-like satellite, called LICIACube and released by the spacecraft over the river, is expected to pass about 55 km from the asteroid to take images of the ejecta.
The event should also be observed by the Hubble and James Webb space telescopes, which should detect a bright cloud of dust and thus help evaluate the amount of material ejected.
All of this should make it possible to better understand the composition of Dimorphos, representative of a population of relatively common asteroids, and therefore to measure the exact effect that this technique can have – called the kinetic effect – on them.
The European Hera probe, which will fly in 2024, will also closely observe Dimorphos in 2026 to assess the consequences of the impact and calculate, for the first time, the mass of the asteroid.
There is currently no danger
Asteroids have held surprises for scientists in the past. In 2020, the American probe Osiris-Rex sank further than expected on the surface of the asteroid Bennu. Likewise, the composition of Dimorphos is currently unknown.
“If the asteroid responds to the Dart impact in an unexpected way, it may lead us to reconsider the extent to which the kinetic impact is a generalizable technique,” warns principal scientist Tom Statler last week.
66 million years ago, the dinosaurs probably disappeared after an asteroid about 10 kilometers wide collided with the Earth.
Nearly 30,000 asteroids of all sizes are listed around the Earth (they are called near-Earth objects, that is, their orbit crosses our planet). Today, none of these known asteroids threaten our planet in the next 100 years. Except they are not all listed yet.
Those of a kilometer or more were almost all found, according to scientists. But they estimate that only about 40% of the asteroids they know measure 140 meters or more — ones capable of destroying entire regions.