NASA to deviate asteroid in 'planetary defence' mission

NASA to deviate asteroid in 'planetary defence' mission
Illustration of DART craft approaching asteroids. © NASA/Johns Hopkins

In less than a year, a spacecraft deployed by NASA will crash into an asteroid to deviate it from its course.

The operation, termed a “planetary defence” mission, is aimed at enabling humanity to be prepared in the event of a threat of impact. No large asteroids are on a collision course, but the exercise is aimed at preparing for such an eventuality, Belga News Agency reports.

“We don’t want to find ourselves in a position where an asteroid is heading towards Earth and we have to test this technique for the first time,” Lindley Johnson of NASA’s planetary defence department said on Thursday.

The mission, known as a Double Asteroid Redirection Test (DART), will take off from California on a Space X Falcon 9 rocket on 23 November. It will hit its target, which will then be located 11 million kilometres from Earth, 10 months later.

The target is twofold: first a large asteroid, Didymos, measuring 780 metres in diameter, and a moon in orbit around it, Dimorphos, 160 metres in diameter. It is on this moon that the ship, about a hundred times smaller than it, will finish its race, projected at a speed of 24,000 km/h.

The impact will project tons and tons of material, but “that’s not going to destroy the asteroid. It’s just going to give it a little kick,” said Nancy Chabot, from the applied physics lab at Johns Hopkins University, which is leading the mission in partnership with NASA. Thus, the orbit of the small asteroid around the big one will be reduced by only “about 1%,” she explained.

In this way, “if one day an asteroid is discovered on a collision course with Earth […] we will have an idea of how much force we will need to make this asteroid miss Earth,” Andy Cheng of Johns Hopkins University, said.

The orbit around the Sun of Didymos, the large asteroid, will be slightly modified, due to the gravitational relationship with its moon, he added. But this change is “too small to be measured, so it’s a very safe experience.”

About 27,000 asteroids near the blue planet are known at present. Asteroid Bennu, which measures 500 metres in diameter, is one of two identified asteroids in our solar system posing the most risk to Earth, according to NASA. But by 2300, the risk of a collision is only 0.057%.

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