NASA is testing whether, in an emergency, it could deflect an asteroid from its course towards Earth and is targeting an astronomical object called Dimorphos. The experiment works so far. Whether it was a success across the board will only be known later.
For the first time, the US space agency NASA has intentionally let a spacecraft fly into an asteroid in order to change its trajectory. NASA’s Dart smashed into the asteroid moon Dimorphos overnight at more than 20,000 kilometers per hour, live images showed. “Impact confirmed for world’s first planetary defense test mission,” NASA announced. With the mission, she wants to test whether and how she can protect Earth from approaching celestial bodies.
The probe for the spectacular “Double Asteroid Redirection Test” experiment, or Dart for short, was launched in California in November 2021. On Tuesday morning, at 1:14 a.m. CEST, it hit the asteroid moon Dimorphos, which orbits the asteroid Didymos eleven million kilometers from Earth.
At the control center in Laurel, Maryland, engineers and scientists erupted in cheers when the transmission ended after the collision. “We’re entering a new era – one where we might be able to protect ourselves from something like a dangerous asteroid impact,” said NASA’s chief of planetary science, Lori Glaze.
Dimorphos, which is about the size of an Egyptian pyramid at 160 meters in diameter, was first seen as a flare on NASA’s live images about an hour before the collision. In the last few minutes before impact with the probe, which was about the size of a car, even its rocky surface could be seen.
NASA wants to use the experiment to test whether it is possible to change the course of an asteroid. The orbit of Dimorphos is to be slightly changed as a result of the impact: the orbital period of just under twelve hours is to be shortened by up to ten minutes. To steer a dangerous asteroid past Earth would require only minimal course changes with early intervention.
The extent to which the asteroid was successfully diverted from its orbit will only be known in a few weeks or months. Telescopes on Earth and satellites in space will observe Dimorphos and measure whether it orbits Didymos slightly faster than before after the experiment. If so, the orbit has been successfully modified.
The probe itself was destroyed in the collision with Dimorphos. A few minutes after the impact, however, a small satellite, which undocked from the spacecraft a few weeks ago, should fly past the collision site and provide close-up pictures of it. However, it will take weeks and months for these images to reach Earth. Telescopes on Earth and in space, including the extremely powerful James Webb telescope, will also observe the experiment.
For an even more detailed investigation, the European Space Agency (ESA) wants to send out its probe Hera in 2024, which should reach the asteroid two years later. The mission, in which the German Aerospace Center (DLR) is significantly involved, is to analyze the nature of Dimorphos and the effects of the impact.
Of the billions of asteroids and comets in our solar system, very few are classified as potentially dangerous to Earth. No impact is expected for the next 100 years. But “I guarantee you, if you wait long enough, there will be an object,” said NASA chief scientist Thomas Zurbuchen.
This is also taught by space history: about 66 million years ago, the Chicxulub asteroid, which is about ten kilometers in size, hit what is now Mexico. It ensured a long winter and is associated with the extinction of the dinosaurs and three quarters of all other species at that time. The impact of an asteroid the size of Dimorphos would only have regional effects. But it would have more force than any atomic bomb and could destroy an entire city.
