NASA / Johns Hopkins APL
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News from the NOS•today, 19:32
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At 1:14 this evening, a high-speed US space probe will collide with a space rock. And that is precisely the point. NASA is studying whether such a maneuver could change the course of an asteroid that threatens to hit Earth.
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Just to reassure you: there is no danger, this is a test. The target is Dimorphos, a 160-meter-wide asteroid that orbits its older sister Didymos at around 750 meters. Together they revolve around the sun in 770 days. They are approaching Earth this year within 10.6 million kilometers. Space rocks are not on a collision course with Earth, nor can a collision accidentally push them towards us.
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It is the first time that it has been tested whether the Earth can be defended in this way. DART, which stands for Double Asteroid Redirection Test, was launched in November 2021 for it.
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Here’s how the trip to Dimorphos went:
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The threat from space doesn’t seem very big at the moment. Of all the asteroids that orbit the Sun near Earth, none larger than 140 meters will hit in the next century.
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But NASA also estimates that we still don’t know half of all asteroids. Furthermore, even the smallest boulders can cause enormous destruction. And in the long run, it is almost inevitable that one day another dangerous boulder will strike. This is why it is wise to test which defense works.
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Scientists have already devised various defense methods. Many people will see the film Armageddon thought, in which a boulder is detonated with an atomic bomb.
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DART makes the transition from action film to reality, albeit in a slightly less spectacular way: the asteroid gets a “push”. By changing the course in good time, a rock misses the land at a considerable distance.
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Extremely high speed
However, hitting the target isn’t that easy. “You try to hit something small that moves with something that moves even at high speed,” says Michel van Pelt. This engineer from the European Space Agency ESA will bite the nail follow the live tonight.
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DART is so far away that it takes 1.5 minutes to get instructions. Since the spacecraft flies at more than 24,000 kilometers per hour, this means that DART is already more than 500 kilometers away. And that while the target is so small that the DART camera can distinguish the rock from the larger Didymos rock it orbits an hour before impact.
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NASA made a schematic representation of the mission’s purpose:
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NASA / Johns Hopkins APL
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For the past four hours, DART then flies entirely on autopilot. A special tool uses information from, among other things, camera images and the position of stars in the sky.
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‘Missing is the end of the mission’
“If they miss the asteroid, the mission is immediately over. So it’s completely failed. You can’t do a U-turn,” says Van Pelt. We will probably know soon if it will be a success. DART has a built-in camera that takes photos up to 5 seconds before impact. The antennas on Earth remain in contact until the last.
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Three minutes after the collision, an Italian mini-satellite flies away to heal the damage. LICIAcube disconnected for this on September 11th. Telescopes from Earth monitor changes in Dimorphos’ orbit.
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It is not clear what effect the collision will have. It depends on the composition of the asteroid. You might get a hard bang on hard. DART then creates a deep crater and a lot of material is thrown into space.
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But asteroids are often not massive but very porous. DART would then disappear deep into space rock without much effect. “If we knew what was going to happen, we shouldn’t do it,” says van Pelt. It is precisely the knowledge gained that should help improve existing computer models.
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The next mission takes damage
With the HERA mission, ESA will investigate the collision even more thoroughly in the coming years. This spacecraft will travel to Didymos and Dimorphos in 2024 and will take a much more detailed look at what happened and measure how the orbit has changed.
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Furthermore, if a deep crater is created, HERA can even see the interior of the asteroid, about which little is known. This will require some patience: HERA is expected to arrive at its destination in December 2026.
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