A NASA spacecraft hit an asteroid in order to deflect it, a first – rts.ch

Confirmed impact: During an unprecedented test mission, a NASA spacecraft deliberately crashed on an asteroid on Monday in order to deviate its trajectory and learn how to protect itself from a potential future threat. It will be necessary to wait a few days to know if the trajectory of the asteroid has indeed been altered.

The ship, smaller than a car, rushed at a speed of more than 20,000 km/h on its target, reached at the scheduled time (1h14 in Switzerland). The NASA teams, gathered at the mission control center in Maryland, in the United States, exploded with joy at the moment of the collision.

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A few minutes before, the asteroid Dimorphos, located about 11 million kilometers from Earth, has gradually grown on the spectacular images broadcast live by the ship. We could clearly distinguish the pebbles on its gray surface, just before the images stop at the moment of the explosion.

“We are embarking on a new era, where we potentially have the ability to protect ourselves from a dangerous asteroid impact,” said Lori Glaze, director of planetary sciences at NASA.

>> The details of 12:45 p.m.:

A NASA probe has succeeded in colliding with an asteroid… 7 million km from the earth… objective to modify its trajectory / 12:45 / 1 min. / today at 12:45

“Planetary Defense”

Dimorphos is about 160 meters in diameter and poses no danger to our planet. It is actually the satellite of a larger asteroid, Didymos, which it has so far circumnavigated in 11 hours and 55 minutes. NASA is looking to reduce Dimorphos’ orbit by 10 minutes, that is, to bring it closer to Didymos.

>> Read also: A kamikaze ship will hit an asteroid to deflect its trajectory

It will take a few days to a few weeks before scientists can confirm that the trajectory of the asteroid has indeed been altered. They will do this thanks to telescopes on Earth, which will observe the variation in brightness as the small asteroid passes in front and behind the large one.

If the goal remains modest compared to the disaster scenarios of science fiction films like “Armageddon”, this “planetary defense” mission is the first to test such a technique. Named DARTfor “Double Asteroid Redirection Test” (an acronym which also means “dart” in English), it allows NASA to train in case an asteroid one day threatens to hit the Earth.

>> A NASA video summarizing this asteroid deflection mission in computer-generated images:

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ATLAS, for “Asteroid Terrestrial-impact Last Alert System”, a NASA and University of Hawaii project monitors the skies every night in search of approaching asteroids, thanks to four terrestrial telescopes. The program observed the DART probe crashing into Didymos (center of image). The flash of the impact is clearly visible, as well as the dust ejected into space:

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Closely scrutinized

The ship had traveled for ten months since its takeoff in California. To hit a target as small as Dimorphos, the last phase of flight was fully automated, like a self-guided missile.

The Dimorphos asteroid 160 meters in diameter compared to the Colosseum in Rome. The DART spacecraft collided with this object on September 26, 2022, which is in orbit around the largest asteroid Didymos, 780 meters in diameter, with the aim of changing its orbit. In 2026, ESA’s Hera probe will arrive in the Didymos system to carry out a close study of the deviated asteroid. [Science Office – ESA]Three minutes after impact, a shoebox-sized satellite – called LICIACube, developed by ASI, the Italian space agency – and released by the spacecraft upstream, was to pass about 55 kilometers from the asteroid to capture images of the ejecta. The event was also to be observed by the Hubble and James Webb space telescopes, which should be able to detect a bright cloud of dust and thus help to assess the amount of material ejected.

All this should make it possible to better understand the composition of Dimorphos, representative of a population of fairly common asteroids, and therefore to measure the exact effect that this technique – called kinetic impact – can have on them. The European probe Herawhich is due to take off 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.

Unknowns

Asteroids have held surprises for scientists in the past. In 2020, the American probe Osiris-Rex had sunk much more than expected into the surface of the asteroid Bennu. Likewise, the composition of Dimorphos is currently not known.

>> Lire: Bennu, the asteroid with a 0.057% chance of hitting Earth et The Osiris-Rex probe made contact with the asteroid Bennu

“If the asteroid responds to the DART impact in a completely unforeseen way, it could actually lead us to reconsider the extent to which kinetic impact is a generalizable technique,” chief scientist Tom Statler warned last week. of the mission.

66 million years ago, the dinosaurs disappeared after the collision of an asteroid about 10 kilometers large with the Earth. Nearly 30,000 asteroids of all sizes have been cataloged in the vicinity of the Earth: they are called “near-Earth cruisers”, that is to say that their orbit crosses that of our planet.

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