Space: what you need to know about the DART mission, whose objective is to deflect an asteroid

The experience is inevitably reminiscent of the movies Armageddon Where Deep Impact, released in 1998. In these feature films, the Earth is threatened by a large asteroid and comet. The collision would be synonymous with cataclysm or even the end of humanity. To avoid the worst, men and women then try to detonate these celestial bodies. This scenario, described as “planetary defense” by NASA, goes from fiction to reality with the mission which takes off, Tuesday, November 23, from California. Its name: DART (“dart” in English). Franceinfo details everything you need to know about this $ 330 million (293 million euros) project which intends to collide with an asteroid to change its orbit.

A kamikaze ship towards an asteroid system

The DART mission will visit a dual system – this is the acronym of “Double Asteroid Redirection Test” – located 11 million kilometers from Earth. It consists of a main asteroid, Didymos, which measures 780 meters in diameter. In orbit of the latter is another smaller asteroid, Dimorphos, which is a moon 160 meters in diameter.

Screenshot of a NASA video presenting the DART mission, the system of the asteroid Didymos and its moon, Dimorphos.  (NASA / YOUTUBE)

The ship, with a wingspan of 19 meters, the equivalent of a large bus, will take off aboard a SpaceX Falcon 9 rocket. It only has a camera necessary for its navigation. Because DART’s mission is kamikaze: it involves hitting Dimorphos, in the fall of 2022, at a speed of 24,000 km / h. In other words, during the last second before the shock, DART will travel 6 km.

Artist's impression of the NASA DART spacecraft.  (NASA / JOHN HOPKINS APL)

The mission that takes off this Tuesday also carries a small observation satellite designed by the Italian space agency. This instrument, called LICIACube (for Light Italian CubeSat for Imaging Asteroids) and composed of two cameras, will separate from the main vessel about ten days before the event to position itself so as to film the crash and quickly transmit the first images to the Earth.

An objective of modifying the orbit of the asteroid

“The Didymos system is the ideal candidate for DART because it poses no threat of real impact to Earth and scientists can measure the change in orbit of Dimorphos with telescopes on the ground”, explains NASA to justify this mission. The objective of the mission is not to destroy the moon-asteroid Dimorphos, but to alter its orbit slightly, without touching Didymos’s orbit (which could make it potentially dangerous for Earth).

The ship “just go give it a little kick”, explained at a press conference Nancy Chabot, from the applied physics laboratory at Johns Hopkins University, which is leading the mission in partnership with NASA.

Dimorphos’ orbit will be reduced by only “about 1%”, specifies Nancy Chabot. Dimorphos currently goes around Didymos in 11 hours and 55 minutes. After the shock, the orbit may be “11 hours and 45 minutes, or something like that”, she detailed.

NASA infographic illustrating the expected result of the impact of the DART spacecraft in the orbit of Dimorphos.  (NASA / JOHNS HOPKINS APL)

A test to prepare humanity for a possible collision

If the probability of a critical impact with an asteroid or a comet is not immediately, the goal of DART is to test now a device of “planetary defense”, for future generations. “We don’t want to find ourselves in a position where an asteroid is heading towards Earth, and where we have to test this technique.” for the first time, detailed at a press conference Lindley Johnson, the Department of Planetary Defense of NASA.

“We are trying to provide a valid plan for the next generations and we want to avoid improvisation.”

Patrick Michel, astrophysicist at the Côte d’Azur Observatory

to franceinfo

Patrick Michel highlights many parameters to be taken into account with this type of risk, mentioning the scientific, technological, political and ethical dimensions. It is in order to “prepare things well”, by integrating all these aspects, that such a mission must be experienced, he insists, calling to avoid any catastrophism. Because the risk of a major collision is “minimal”, assures franceinfo Eric Lagadec, astrophysicist at the Observatory of the Côte d’Azur, specifying that this is not planned in the years to come. There is no “no known object that threatens us for the next century at least”adds Patrick Michel.

In detail, according to NASA data, all asteroids about 10 km in diameter (like the one that caused the dinosaurs to disappear 66 million years ago) in the vicinity of Earth have been identified. . There are four of them. If a celestial body of this size hit our planet, it would cause a major catastrophe. But that only happens every 100 million or 200 million years. About 900 asteroids 1 km in diameter have been identified on the outskirts of the Earth. They cross Earth’s path roughly every 500,000 years, and a collision with one could cause mass extinction.

Regarding asteroids 140 meters in diameter (the size of the moon that DART will hit), specialists estimate their number at 25,000. Only 40% of them are known, and they cross our path. planet approximately every 20,000 years. If a body of this size were to crash into Paris, at least the entire Ile-de-France region would be instantly destroyed, reported Le Figaro. The human toll would be dramatic and the consequences planetary.

The first part of a twin mission to understand asteroids

Originally, the DART ship was not to go alone: ​​it had to take off at the same time as the Hera mission, which must “provide us with the detailed results of the impact, allow us to interpret the first measurements made with terrestrial telescopes and to extrapolate to other scenarios”, details the French Patrick Michel, main instigator of the Hera mission. But ultimately, the Hera mission will not take off until 2024.

“The data from the Hera mission will allow us to transform this large-scale DART impact experience into a well-understood and repeatable technique.”

Naomi Murdoch, planetologist involved in the Hera mission

to franceinfo

These missions “binoculars” are “a fundamental experiment to verify our understanding of the physics of impacts on asteroids, which is at the heart of the deflection technique that we are going to test”, explained Patrick Michel on the website of the European Space Agency.

In addition to the study of impacts, that of asteroids is of great interest to scientists. They hope to better understand the mechanism that led to the formation of Dimorphos. One of the scenarios is that this asteroid is made up of volatile matter coming directly from its big neighbor, Didymos. This would mean that Dimorphos is made of dust, that it is “an aggregate structure and not a compact structure”, remarks Alain Hérique, of the Institute of planetology and astrophysics of Grenoble.

More generally, approaching asteroids can only prove beneficial for the advancement of knowledge. “Asteroids are the building blocks that shaped our solar system, recalls Eric Lagadec. As soon as we can approach them and observe them better, we learn more about its formation and evolution. “

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