Confirmed impact: A NASA spacecraft purposely crashed into an asteroid to deviate from its trajectory on Monday during an unprecedented test mission designed to allow humanity to learn how to protect itself from a potential future threat.
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The ship, smaller than a car, sped towards its destination at a speed of more than 20,000 km/h, reaching it at the scheduled time (23:14 GMT). Nasa teams gathered at the Mission Control Center in Maryland, USA, 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.
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.
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 is modest compared to the catastrophic scenarios of sci-fi movies like Armageddon, this Planetary Defense mission dubbed Dart is the first to try such a technique. This allows NASA to train if one day an asteroid threatens to hit Earth.
Scrutinized closely
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.
Three minutes after impact, a shoebox-sized satellite called LICIACube, released upstream from the spacecraft, was scheduled to fly by about 55 km 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 help to better understand the composition of Dimorphos, which are representative of a population of fairly common asteroids, and therefore measure the precise effect this technique – the so-called kinetic impact – can have on them.
The European probe Hera, which is scheduled to launch in 2024, will also observe Dimorphos closely in 2026 in order to assess the consequences of the impact and to calculate the asteroid’s mass for the first time.
unknown
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 Dart’s impact in a completely unpredictable way, it could actually make us reconsider the extent to which 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 NEOs, meaning their orbits intersect that of our planet).
Today none of these known asteroids threaten our planet for the next 100 years. Except that not all of them are listed yet.
Almost all of the animals have been sighted from a kilometer or more, according to the scientists. But they estimate they only know about 40% of asteroids 140 meters or larger in size – the ones that can devastate an entire region.
“Our most important task is to find the missing,” said NASA planetary defense officer Lindley Johnson. The earlier they are discovered, the more time the experts have to fight back.
The Dart mission is a crucial first step in this direction, according to Mr. Johnson: “This is a very exciting time (…) for the history of space and even for the history of mankind.”