NASA has deflected the asteroid Dimorphos with the impact of the “Dart” probe. The US space agency has thus proven: In this way, the collision of a celestial body with the earth can be prevented.
Two independent observation series confirmed it on Tuesday evening. With the impact of 570 kilograms heavy dart probe the orbit of the asteroid Dimorphos was actually changed. The 160 meter large celestial body orbited its much larger companion Didymos (780 meters) before the collision in 11 hours and 55 minutes. However, after the dart hit at 6.1 kilometers per second (22,000 km/h) on the night of September 26/27, the trajectory changed – by 32 minutes. Dimorphos now orbits Didymos in eleven hours and 23 minutes.
Both the observations with telescopes and radar measurements have confirmed the historical result: for the first time in human history we have successfully changed the orbit of a celestial body. And it’s a real-time test if an asteroid is on a collision course with Earth. With catastrophic consequences.
The deflection is in the high range of estimates for the mission. One reason for this is the enormous amount of material ejected. The effect of the impact was amplified by the recoil during ejection, the scientists said at a press conference held by the US space agency Nasa on Tuesday evening. And how powerful the impact was can be seen in the images from the Hubble and James Webb space telescopes. But above all in the recordings of the Italian satellite “LiciaCube”. Measuring only 20 by 30 by 30 centimeters, the companion of the Dart probe had been undocked 15 days before the collision in order to observe the impact up close.
There are still many unanswered questions that should be clarified by further observations and analyses: What is the mass of the ejected material and how big are the particles? At what speed were they ejected? How did the orbit of Dimorphos change in detail? And what is the exact mass of the two celestial bodies? Even more data will be collected when the European Space Agency Esa will use the Hera probe to study Dimorphos and Didymos up close in 2027.
But the successful test showed that you can deflect an asteroid. To protect the earth, said Nasa boss Bill Nelson at the press conference. The next step will now be to record all potential threats and to identify a danger at an early stage. After all, only 40 percent of the near-Earth asteroids the size of Dimorphos are known. And the sooner you deflect an asteroid in an emergency, the smaller the change in orbit must be. The Dart mission would provide data on how efficient the technology is. The probe itself, for example, was only 1.2 by 1.3 by 1.3 meters without instruments and still had a big effect. And that will refine the models. After all, not all of these celestial bodies are the same. Some are loose piles of rubble, some are made out of large shards of rock, and some are actually solid “rocks”. Thanks to Dart and five years from Hera, there will be better predictions of how these different types will behave in a collision.