The threat an asteroid poses to Earth has already been discussed in Hollywood movies like Armageddon. Far from fiction, astronomers are currently unaware of any threatened asteroids. However, the US space agency NASA wants to be prepared. “We are now entering a new era of humanity where we may have the opportunity to protect ourselves from an asteroid impact,” NASA Administrator Laurie Glaese says after the successful mission.
In images sent back to Earth by the probe’s camera, the asteroid Demorphos became visible only as a bright spot about an hour before the collision, then grew in size and finally appeared with surface detail and shading – until the camera was destroyed on impact and that image displayed a red error.
There was relief at NASA’s Control Center. The probe, which flew at 6.6 kilometers per second, had been on autopilot for the past few minutes and it was not entirely clear if it would actually hit the asteroid.
A distraction instead of destruction
NASA’s $325 million Double Asteroid Redirection Test (DART) mission has put the “safety of Earth’s future” on the line for NASA. This is the first time that a risky project has been avoided through direct experience, said Thomas Zurbuchen, NASA’s director of science. The Dart probe was launched last November with a “Falcon 9” missile from California, USA.
The collision at 23,000 kilometers per hour should slightly alter the trajectory of the asteroid’s moon Demorphos around Didymos. Mission team leader Nancy Chabot said it was about deflecting an asteroid, not destroying it. Subsequent investigations will now show if the collision actually changes the course of about 12 hours.
There was no risk in the experiment. Demorphos, about 160 meters in diameter, and the larger 780-meter asteroid Didymos, which orbits Demorphos, were at least about 11 million kilometers from Earth. Had the spacecraft missed the asteroid’s moon, the spacecraft would have had enough fuel for a second attempt in two years.
The DART mission was accompanied by ground-based telescopes, including the James Webb Telescope, as well as cameras on the site. The spacecraft’s camera system sent images of the Dimorphos back to Earth until the impact. Then, a toaster-sized satellite, which was detached from the DART spacecraft a few weeks ago, must fly through the impact site and provide close-up images. However, it will be a few weeks and months before the images hit Earth. Only then will it be certain whether the orbit has actually changed.
27,000 asteroids near Earth
In 2024, the European Space Agency (ESA) will send the Hera probe on a two-year journey to study the impact site and the surface of the Dimorphos in more detail. Over the next 100 years, scientists do not see any asteroid threatening the Earth. If you wait too long, Zurbuchen said, there will be a body. Scientists have identified about 27,000 asteroids near Earth, about 10,000 of which are more than 140 meters in diameter.
An asteroid collision has already occurred. 66 million years ago, the Chicxulub asteroid, which was about 10 kilometers in diameter, struck what is now Mexico, causing a permanent winter and linked to the extinction of the dinosaurs.