The DART probe will hit the asteroid Dimorphos in the evening

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The DART probe will hit the Dimorphos asteroid in the evening

Artist's rendering of the DART probe and the asteroid Dimorphos

In an exercise to deflect a possible threat to Earth, NASA will fire the DART probe against the asteroid Dimorphos at 19 hours, 14 minutes and 23 seconds (EDT).

This kamikaze mission, the goal of which is to deviate the trajectory of a celestial object, is a test of planetary defense which should make it possible to better protect humanity.

The mission DART (dart, in English, and an acronym for Double Asteroid Redirection Test) took off from California's Vandenberg base aboard a SpaceX Falcon 9 rocket last November.

After ten months of travel, the 570 kilo ship must hit the small asteroid 160 meters in diameter at a speed of more than 20,000 km/h.

This asteroid does not represent a real danger for the Earth since its orbit around the Sun passes only 7 million kilometers from the Earth at its closest. Besides, NASA's goal is not to destroy it, but to push it slightly.

Dimorphos is in orbit around a larger asteroid, Didymos (780 meters in diameter), which it circles in 11 hours and 55 minutes. The goal is to reduce the orbit of Dimorphos around Didymos by about ten minutes.

This change can be measured by telescopes from Earth, observing the variation in brightness as the small asteroid passes in front of the large one.

The goal may seem modest, but this demonstration is crucial for the future. It is a question of better understanding how Dimorphos will react, which represents a population of fairly common asteroids, but whose exact composition is not known. The effect of the impact will largely depend on its porosity, i.e. whether it is more or less compact.

To hit such a small target, the ship will steer autonomously for the last four hours, like a self-guided missile. His camera will take the very first images of the asteroid at the last moment at a rate of one frame per second.

These images will reach Earth with a delay of only about 45 seconds.

“It will start with a small point of light, until it fills the whole frame.

—Nancy Chabot, Johns Hopkins University Applied Physics Laboratory (APL)

These images will continue to arrive, until #x27;they're not coming anymore, Ms. Chabot added, referring to the time of the explosion.

Three minutes later, a shoebox-sized satellite called LICIACube, released by the craft a few days ago, will pass about 55 km from the asteroid to take images of the ejecta. They will be sent back to Earth in the following weeks and months.

The event will also be observed by the Hubble and James Webb space telescopes, which should be able to detect a cloud of dust shiny.

Then the European HERA probe, which is due to take off in 2024, will closely observe Dimorphos in 2026 to assess the consequences of the impact and calculate, for the first time, the mass of the asteroid.

Very few of the known asteroids are considered potentially dangerous, and none are for the next 100 years.

But I guarantee that if you wait long enough, there will be an object, said NASA chief scientist Thomas Zurbuchen.

Nearly 30,000 asteroids of all sizes have been cataloged in the vicinity of Earth (they are called near-Earth objects, meaning that their orbit crosses that of our planet). About 3,000 new ones are found each year.

Those a kilometer or more have nearly all been spotted, scientists say. But they estimate they only know about 40% of asteroids that are 140 meters and larger – those capable of devastating an entire region.

If DART misses its target, the ship should have enough fuel for another attempt in two years.

And if the mission succeeds, it will be a first step towards a real defense capability, according to Nancy Chabot. Earth has been hit by asteroids for billions of years, and it will happen again. As humans, let's make sure we live in a civilization where we can avoid it.

With information from Agence France-Presse

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