Confirmed impact: During an unprecedented test mission on Monday, a NASA spacecraft intentionally crashed into an asteroid to deviate from its trajectory and learn how to protect against a potential future threat. It will take a few days to know if the asteroid’s trajectory has actually changed.
The ship, smaller than a car, sped towards its destination at a speed of over 20,000 km/h, which was reached at the scheduled time (1h14 in Switzerland). NASA teams gathered at Mission Control Center in Maryland, United States, exploded with joy at the moment of the collision.
A few minutes earlier, the asteroid Dimorphos, some 11 million kilometers from Earth, has gradually grown in the spectacular images broadcast live by the ship. We could clearly see the pebbles on its gray surface just before the images stopped at the moment of the explosion.
“We’re entering a new era where we may have the ability to protect ourselves from a dangerous asteroid impact,” said Lori Glaze, director of planetary sciences at NASA.
>> The interview with astrophysicist Raoul Behrend at 7:30 p.m.:
Dimorphos is about 160 meters in diameter and poses no threat to our planet. It is actually the satellite of a larger asteroid, Didymos, which it has orbited in 11 hours and 55 minutes so far. NASA is trying to shorten Dimorphos’ orbit by 10 minutes, that is, bring it closer to Didymos.
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It will be a few days to weeks before scientists can confirm that the asteroid’s trajectory has indeed been altered. They will do so thanks to telescopes on Earth, which will observe the fluctuations in brightness as the small asteroid passes in front of and behind the big one.
If the goal remains modest compared to the catastrophic scenarios of science fiction films like “Armageddon”, this “Planetary Defense” mission is the first to test such a technique. Calledfor “Double Asteroid Redirection Test” (an acronym that also means “arrow” in English), allows NASA to train in case an asteroid threatens to hit Earth one day.
>> A NASA video summarizing this asteroid deflection mission in computer generated imagery:
, for “Asteroid Terrestrial-impact Last Alert System”, a project of NASA and the University of Hawaii, uses four terrestrial telescopes to monitor the sky every night in search of approaching asteroids. The program observed how the DART probe impacted Didymos (centre of image). The flash of impact can be clearly seen, as can the dust being flung into space:
The ship had been ten months since its launch in California. To hit such a small target as Dimorphos, the final phase of flight was fully automated, like a self-guided rocket.
The asteroid Dimorphos has a diameter of 160 meters compared to the Colosseum in Rome. The DART spacecraft collided with this object orbiting the largest asteroid Didymos, 780 meters in diameter, on September 26, 2022, with the aim of changing its orbit. In 2026, ESA’s Hera probe will arrive in the Didymos system to conduct a close study of the deflected asteroid. [Science Office – ESA]Three minutes after impact, a shoebox-sized satellite called , developed by the Italian space agency ASI and released upstream by the spacecraft, was scheduled to fly by about 55 kilometers from the asteroid to capture images of the ejecta. The event should also be observed by the Hubble and James Webb Space Telescopes, which should be able to spot a bright dust cloud, helping estimate the amount of material being ejected.
All of this should make it possible to better understand the composition of Dimorphos, which are representative of a population of fairly common asteroids, and therefore to measure the precise effect that this technique – called kinetic influence – can have on them. The European probescheduled for launch in 2024, Dimorphos will continue to watch closely in 2026 to assess the impact’s consequences and calculate the asteroid’s mass for the first time.
Asteroids have always surprised scientists in the past. In 2020, the American probe Osiris-Rex had sunk into the surface of the asteroid Bennu much more than expected. Likewise, the composition of Dimorphos is currently unknown.
“If the asteroid reacts to the DART impact in a completely unpredictable way, that could actually make us reconsider the extent to which the kinetic impact is a generalizable technique,” warned chief scientist Tom Statler ahead of the mission last week.
Dinosaurs disappeared 66 million years ago after an asteroid about 10 kilometers across collided with Earth. Nearly 30,000 asteroids of all sizes have been cataloged near Earth: they are called “near-Earth cruisers,” meaning their orbits intersect that of our planet.
>> The details of La Matinale:
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