In less than a year, a NASA spacecraft will deliberately crash into the surface of an asteroid.
The target; To make him deviate from his course. This mission, which is characterized as a “planetary defense” mission, is expected to allow humanity to be prepared for the threat of an asteroid impact in the future.
The script is reminiscent of that of the movie “Armageddon”, in which Bruce Willis and Ben Affleck save the planet from a huge asteroid heading towards Earth.
But the US space agency is conducting a very real experiment here. Although no known large asteroid is currently in collision, the point is to prepare for this eventuality.
“We do not want to be in the position where an asteroid will be headed towards Earth and we will have to try this technique then,” Lindley Johnson of NASA’s Planetary Defense Department told a news conference on Thursday.
The mission, dubbed DART (double arrow in the Asteroid Double Asteroid Redirection Test), will take off from California with a SpaceX Falcon 9 rocket at 22:20 (local time) on November 23rd.
Ten months later, the spacecraft will hit its target, which will then be eleven million kilometers from Earth – that is, the moment it is the shortest distance from Earth.
– “A little blow” –
In fact, the goal is twofold: first a large asteroid, Gemini, which is 780 meters in diameter, ie twice the height of the Eiffel Tower.
And in orbit around him, a moon, Dimorphos, 160 meters in diameter – taller than the Statue of Liberty.
Exactly on this moon is that the boat, which is about a hundred times smaller than this one, will finish its race, at a speed of 24,000 km / h.
The impact will launch tons of material into space.
But “it will not destroy the asteroid, it will just give it a small blow,” said Nancy Chabot of Johns Hopkins University’s Applied Physics Laboratory, which is leading the mission in partnership with NASA.
So the orbit of the small asteroid around the big one will only decrease by “about 1%”, he explains.
Thanks to the observations made for decades with the telescopes on Earth, we know that Dimorphos is currently making a complete rotation around Gemini in exactly 11 hours and 55 minutes.
With the help of these same telescopes, this period will be measured again after the collision. It will then probably be “11 hours and 45 minutes or something,” says the researcher.
How exactly? Scientists do not know and this is exactly what they want to discover. Numerous factors enter the equation, including the angle of impact, the surface appearance of the asteroid, its composition or even its exact mass, elements unknown until now.
In this way, “if one day an asteroid is discovered in the course of a collision with the Earth, (…) we will have an idea of ​​the power we will need so that this asteroid does not reach the Earth,” he explained. Andy Cheng of Johns Hopkins University.
The orbit of Gemini, the large asteroid, around the Sun will also be slightly modified due to its gravitational relationship with its moon, Cheng said. But this change will be “too small to measure. It is therefore a very safe experiment, “he explained.
– Toolbox –
A small satellite will also make this trip. He will be released from the main boat ten days before the collision and will use his own propulsion system to deviate slightly from its course.
Three minutes after the collision, it will fly over Dimorphos to observe its effect and possibly the crater on the surface.
The total cost of the shipment is $ 330 million.
If this test is successful, “we believe that this technique could be part of a toolbox that we are beginning to fill so that we can make an asteroid deviate from its course,” explained Lindley Johnson. He mentioned, for example, methods by which the gravitational force of a flying spacecraft could be used near an asteroid over a long period of time, or even the use of a laser.
But he reminded that the key is to identify potential threats first. “The strategy is to find these objects not just years, but decades before any risk of collision with Earth,” he said.
About 27,000 asteroids near the blue planet are currently known.
The Bennu asteroid, 500 meters in diameter, is one of two asteroids found in our solar system that pose the greatest threat to Earth, according to NASA.
But from now until the year 2300, the risk of collision is only 0.057%.
.
