NASA readies DART planetary defense mission to deflect asteroid trajectory

In less than a year, a NASA spacecraft will deliberately crash into an asteroid to deflect its trajectory. Described as a “planetary defense”, this mission should prepare humanity in the event of an impact threat.

The setting is reminiscent of the movie “Armageddon”, In which Bruce Willis and Ben Affleck save the planet from a huge asteroid hurtling toward Earth.

But the US space agency is conducting a very real experiment in this case. Although no large asteroid is known to be on a collision course so far, the idea is to prepare for that possibility.

“We don’t want to be in a position where an asteroid is heading towards Earth; we must try this technique, ”Lindley Johnson of NASA’s Department of Planetary Defense told a news conference Thursday.

The mission, dubbed DART (Double Asteroid Redirection Test), will take off from California aboard a SpaceX Falcon 9 rocket on November 23 at 10:20 p.m. local time.

Ten months later, the spacecraft will hit its target, which will be 11 million kilometers from Earth. In fact, it is the closest you will get to the blue planet.

A little success

Actually, it is a double objective. The main one is the large asteroid Didymos, 780 meters in diameter, that is, twice the height of the Eiffel Tower. In its orbit is a moon, Dimorphos, 160 meters in diameter and taller than the Statue of Liberty.

It is on this moon that the spacecraft will land, about a hundred times smaller than it, projected at a speed of 24,000 km / h. The impact will throw out tons and tons of material.

But “it’s not going to destroy the asteroid, it will just give it a little jolt,” said Nancy Chabot of the Johns Hopkins University Applied Physics Laboratory, which runs the mission in collaboration with NASA.

As a result, the orbit of the smallest asteroid around the largest will be reduced by only “about 1%,” he explained.

From observations made by telescopes on Earth for decades, Dimorphos is known to currently orbit Didymos in exactly 11 hours and 55 minutes.

Using the same telescopes, this period will be measured again after the collision. In that case, it might be “11 hours and 45 minutes, or something like that,” the researcher said.

But how much exactly? Scientists don’t know, and that’s what they want to find out.

There are many factors that come into play, such as the angle of impact, the appearance of the asteroid’s surface, its composition, and its exact mass, all of which are currently unknown.

In this way, “if one day an asteroid is discovered on a collision course with Earth (…) we will have an idea of ​​the force we will need so that that asteroid does not touch Earth,” explained Andy Cheng, from Johns University. Hopkins.

The orbit around the sun of Didymos, the large asteroid, will also change slightly, due to the gravitational relationship with its moon, Cheng said. But this change will be “too small to measure.”

Toolbox

A small satellite will also travel. It will uncouple from the main ship ten days before impact and use its propulsion system to slightly deviate its own trajectory.

Three minutes after the collision, it will fly over Dimorphos, to observe the effect of the impact, and possibly the crater on the surface.

The total cost of the mission is $ 330 million. If the experiment is successful, “we think this technique could be part of a toolbox, which we are beginning to fill, to deflect an asteroid,” explained Lindley Johnson.

For example, he cited methods that could use the gravitational force of a spacecraft flying near an asteroid for a long period of time, or the use of lasers.

But he said the key was to first identify potential threats. “The strategy is to find these objects not just years, but decades before any danger of collision with Earth,” he said.

Currently about 27,000 asteroids are known near the blue planet.

Bennu, which measures 500 meters in diameter, is one of two asteroids identified in our Solar System that pose a greater risk to Earth, according to NASA.

But between now and 2300, the probability of a collision is only 0.057%. (I)