To protect humanity, NASA tries to deflect the path of an asteroid

To protect humanity, NASA is attempting to reverse the trajectory ; an asteroid of

MISE & Agrave; DAY

It’s a Hollywood script, yet very real. NASA took off on the night of Tuesday to Wednesday an unprecedented mission: by projecting a spacecraft at 24,000 km/h against an asteroid, it hopes to change its trajectory and thus help humanity protect itself from a potential collision at the future.

The mission, dubbed DART (dart, in English), took off from California's Vandenberg base aboard a SpaceX Falcon 9 rocket, at 10:21 pm local time on Tuesday .

“Asteroid Dimorphos, we're coming to get you,” NASA tweeted after the launch.

A few hours before takeoff, the weather conditions remained favorable for a launch at the expected time, SpaceX had reported.

This test “will be historic,” said Tom Statler, a NASA scientist participating in the mission, at a press conference. “For the first time, humanity will change the motion of a natural celestial body in space.”

This is only a dress rehearsal, the target asteroid does not represent in no way a threat to Earth. But the target is taken very seriously by the US space agency.

It currently lists just over 27,500 asteroids of all sizes close to Earth and “none of them represents a threat in the next hundred years or so”, reassured Thomas Zurbuchen, director for scientific missions at the NASA.

But experts estimate that they know only 40% of asteroids measuring 140 meters or more – those capable of devastating an entire region – with the majority yet to be discovered. The idea is therefore to develop a technique to protect against it in the event of a future threat.

10 short minutes

The mission ship is smaller than a car, flanked by two long solar panels. It is due to strike next fall, in about ten months, an asteroid the size of a football field (about 160 meters in diameter), which will then be located eleven million kilometers from Earth.

The asteroid is called Dimorphos and is actually a moon, orbiting a larger asteroid, itself named Didymos (780 meters in diameter).

To circle the large asteroid, Dimorphos currently takes 11 hours and 55 minutes. Scientists expect to reduce its orbit, by about 10 minutes.

“It's a very small change but it could be all we need to deflect an asteroid with a collision course with Earth, if we ever had to, provided we discovered this asteroid soon enough, ”explained Tom Statler.

The exact effect that the impact will have is not known at the moment because it depends in particular on the composition of the asteroid.

It is this precise change of trajectory, which will then be measured using telescopes from Earth, which scientists want to determine. The results will be used in calculations to help define, in the future, what mass must be projected against a given type of asteroid to cause sufficient deflection.


Is Dimorphos made of solid or more porous rocks? Scientists know nothing about it, and the asteroid will only appear in images transmitted by the spacecraft just an hour before the collision. Its shape, round or oblong, will only be clear 2 minutes before.

Then the explosion, and radio silence.

The following images will come from a small satellite developed by the Italian Space Agency. It will be released from the main ship ten days before impact.

Three minutes after the collision, it will fly over Dimorphos, in order to observe the effect of the shock and, with a little luck, the crater on the surface.

The orbit of the large asteroid Didymos around the Sun could also be slightly modified, due to the gravitational relationship with its moon. But so little that the change cannot be measured. No chance therefore that the asteroid is placed on a new potentially dangerous path for the blue planet.

The total cost of the mission – the first interplanetary launched by Elon Musk's company for NASA – – is $ 330 million.

Other techniques are being considered to deflect an asteroid. For example, by carrying out a nuclear explosion near one of them, not to destroy it but to ricochet off its path. The gravitational force of a ship, flying close to an asteroid for a long time, could also be used.

But the technique tested here, called kinetic impact, is by far the most mature. Provided it proves itself in this test.

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