NASA is going to crash a spaceship on an asteroid in order to deviate its trajectory.
While no known large asteroids are currently on a collision course and threaten Earth, it is a matter of preparing for this eventuality.
"We do not want to find ourselves in a position where an asteroid is heading towards Earth, and where we should test this technique" for the first time, explained Thursday at a press conference Lindley Johnson, of the Department of Planetary Defense from NASA.
The mission, dubbed DART (dart in English and acronym for Double Asteroid Redirection Test), will take off from California aboard a SpaceX Falcon 9 rocket on November 23 at 10:20 p.m. local time. Ten months later, the spacecraft will hit its target, then located eleven million kilometers from Earth, when its distance will be closest to the blue planet.
In reality, the target is twofold: first a large asteroid, Didymos, which measures 780 m in diameter, or twice the height of the Eiffel Tower.
And, in orbit around it, a moon, Dimorphos, 160 m in diameter - taller than the Statue of Liberty.
It is on this moon that the ship, about a hundred times smaller than it, will come to finish its race, projected at a speed of 24,000 km / h.
The impact will project tons and tons of matter, but "it's not going to destroy the asteroid, it's just going to give it a little kick," said Nancy Chabot, of the applied physics laboratory at Johns Hopkins University, which leads the mission in partnership with NASA.
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Thus, the orbit of the small asteroid around the big one will be reduced by only "about 1%", she explained. Thanks to the observations made by telescopes on Earth for decades, we know that Dimorphos currently circles Didymos in exactly 11 hours and 55 minutes. Using these same telescopes, this period will be measured again after the collision. It will then be maybe “11 hours and 45 minutes, or something like that,” the researcher said. How much exactly? Scientists don't know it, and that's exactly what they want to find out. Many factors come into play, including the angle of impact, the appearance of the asteroid's surface, its composition or even its exact mass, unknown until now.
The total cost of the mission is $ 330 million.
If the test is successful, "we think this technique can be part of a toolbox, which we are starting to fill, so as to deflect an asteroid," said Lindley Johnson.
For example, he cited methods that could use the gravitational force of a flying vessel close to an asteroid for a long time, or the use of lasers.
About 27,000 asteroids near the blue planet are known at present.
Asteroid Bennu, which measures 500 m in diameter, is one of two identified asteroids in our solar system posing the most risk to Earth, according to NASA.
But by 2300, the risk of a collision is only 0.057%.