It’s a setting worthy of Hollywood, but very real. NASA took off on the night of Tuesday to Wednesday an unprecedented mission: by designing a spacecraft at 24,000 km / h against an asteroid, it hopes to modify its trajectory and thus help humanity to protect itself from a potential collision in the future.
The mission, dubbed DART, lifted off from California’s Vandenberg base aboard a SpaceX Falcon 9 rocket at 10:21 pm local time Tuesday (7:21 am Swiss time Wednesday).
“Asteroid Dimorphos, let’s get it,” NASA tweeted after launch. A few hours before liftoff, weather conditions remained favorable for a launch at the scheduled time, SpaceX reported.
This test “will be historic”, said Tom Statler, a NASA scientist participating in this mission, during a press conference. “For the first time, humanity will change the motion of a natural celestial body in space.”
no imminent threat
This is just a dress rehearsal, the asteroid in question does not pose a threat to Earth in any way. But the goal is taken very seriously by the American space agency.
It currently lists just over 27,500 asteroids of all sizes near Earth and “none of them pose a threat in the next hundred years,” said Thomas Zurbuchen, NASA’s director of science missions.
But experts estimate that they only know about 40% of asteroids measuring 140 meters or more – those capable of laying waste to an entire region – with the majority yet to be discovered. The idea is therefore to develop a technique to protect you in the event of a future threat.
A small orbit change
The mission ship is smaller than a car, flanked by two long solar panels. It should hit next autumn, 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 called Didymos (780 meters in diameter).
To circumnavigate the large asteroid, Dimorphos currently takes 11 hours and 55 minutes. Scientists hope 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 on a collision course with Earth, if need be, as long as we find that asteroid soon,” explained Tom Statler.
The exact effect the impact will have is not known at the moment because it depends in particular on the composition of the asteroid.
A satellite to observe the shock
It is this precise change in trajectory, which will be measured using Earth-based telescopes, that the scientists want to determine. The results will be used for calculations to help define, in the future, what mass should be hurled at a given type of asteroid to cause sufficient deflection.
About the subject:
Is Dimorphos made of solid rocks or more porous? Scientists don’t know, and the asteroid will only appear in images transmitted by the spacecraft an hour before the collision. Its shape, round or oblong, will only become clear 2 minutes beforehand. Then the explosion and the radio silence.
The following images will come from a small satellite developed by the Italian Space Agency. It will be launched by the main ship ten days before impact. Three minutes after the collision, it will fly over Dimorphos, to observe the effect of the shock and, with any luck, the crater on the surface.
Other techniques considered
The orbit of the large asteroid Didymos around the Sun may also be slightly modified, due to the gravitational relationship with its moon. But so little that change cannot be measured. Therefore, there is no chance that the asteroid will be placed on a new, potentially dangerous trajectory 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, carrying out a nuclear explosion near one of them, not to destroy it, but to deflect its trajectory by ricochet. The gravitational pull of a spacecraft, 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. As long as it proves during this test.