To protect humanity, NASA will divert the trajectory of an asteroid as a test

Steph Deschamps / November 24, 2021

It is a scenario worthy of Hollywood, and yet very real. NASA is preparing to launch a new mission on Tuesday night: by launching a spacecraft at 24,000 km/h against an asteroid, it hopes to modify its trajectory and thus help humanity protect itself from a potential collision in the future. 
This test will be historic, Tom Statler, a Nasa scientist involved in the mission, said at a news conference. For the first time, humanity will change the motion of a natural celestial body in space.
This is only a dress rehearsal, as the target asteroid is not a threat to Earth. But the objective 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, reassured Thomas Zurbuchen, director for science missions at NASA
The mission, dubbed DART, will lift off from California's Vandenberg Air Force Base aboard a SpaceX Falcon 9 rocket at 10:21 p.m. local time Tuesday .
Hours before liftoff, weather conditions remained favorable for a launch on schedule, SpaceX tweeted.
The spacecraft is smaller than a car, flanked by two long solar panels. It is scheduled to strike an asteroid the size of a soccer field (about 160 meters in diameter) next fall, in about ten months, which will then be located eleven million kilometers from Earth
The asteroid is called Dimorphos and is in fact a moon, in orbit around a larger asteroid, 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 on a collision course with Earth, if we ever have to do that, provided we discover that asteroid soon enough, Tom Statler explained.
The exact effect of the impact is not known for the moment because it depends on the composition of the asteroid.
It is this precise change in trajectory, which will then be measured with telescopes from Earth, that the scientists want to determine. The results will be used in calculations to help define, in the future, what mass must be thrown against a given type of asteroid to cause sufficient deflection.
Is Dimorphos made of solid rock or more porous? Scientists do not know, and the asteroid will appear on the images transmitted by the spacecraft only one hour before the collision. Its shape, round or oblong, will be clear only 2 minutes before.
The following images will come from a small satellite developed by the Italian Space Agency. It will be released by the main spacecraft ten days before the impact.
Three minutes after the collision, it will fly over Dimorphos, 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, because of the gravitational relationship with its moon. But so little that the change will not be measurable. No chance that the asteroid is placed on a new trajectory potentially dangerous for the blue planet.
The total cost of the mission the first interplanetary mission launched by Elon Musk's company for Nasa is $330 million.
Other techniques are envisaged to deflect an asteroid. For example, by carrying out a nuclear explosion near one of them, not to destroy it but to deflect its trajectory by ricochet. The gravitational force of a ship, flying close to an asteroid during a long period, could also be used.
But the technique tested here, known as kinetic impact, is by far the most mature. Provided that it proves itself during this test.
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