The vending machine-sized DART spacecraft reached its target, Asteroid Didymos and its moonlet Dimorphos, and promptly slammed into Dimorphos. But that’s okay. That’s what it was supposed to do.
The Double Asteroid Redirection Test (DART) mission involved a test of a proposed asteroid redirect method. Now Earth-based telescopes will spend the next several months studying the impact’s effect on Dimorphos’ orbit around Didymos. An Italian-built probe that accompanied DART will also snap pictures of the impact site from its current position near the asteroids.
Before the DART impactor collided with its target, it managed to send back a few “close-up” images of Dimorphos, revealing a landscape that looked littered with rocks. The last image was sent back just seconds before it stopped sending signals back to Earth.
DART launched in November 2021 and spent ten months traveling to the asteroid. The European Space Agency plans to launch a follow-up mission in 2024 for a close-up study of the effects of the DART impact.
What Are Didymos and Dimorphos?
Didymos and Dimorphos currently reside about 6.8 million miles from Earth in an orbit that won’t make them dangerous to Earth. Didymos is an asteroid that is about 2,500 feet wide at its widest point. Dimorphos is a smaller, 500-foot asteroid that orbits it.
According to theory, the impact should shave about ten minutes off Dimorphos’ orbit and the change in its orbit is expected to grow over time. Observations of the impact’s effects will help refine techniques for deflecting dangerous asteroids.
What Makes Asteroids Dangerous?
Contrary to popular perception from elementary-school models of the solar system, not all asteroids reside in the asteroid belt between Mars and Jupiter. Some of them have orbits around the sun that cross Earth’s orbit. Eventually, a big one could actually slam into Earth.
Current theory holds that a huge asteroid strike triggered a chain of events that caused the dinosaurs to go extinct and that was not even the last potentially dangerous asteroid to enter Earth’s atmosphere.
On June 30, 1908, an asteroid famously flattened 500,000 acres of forest by exploding in Earth’s atmosphere over Siberia’s Tunguska River in an at-first-mysterious catastrophe that came to be known as the Tunguska Impact. Three people died in the Tunguska Impact and experts say that the event could have been much worse if the asteroid had entered Earth’s atmosphere over a more populated area.
In 2013, a tennis court-sized asteroid exploded twenty miles over Chelyabinsk, Russia. This incident shattered windows and flattened trees over an area of hundreds of square miles. It killed 1,600 people.
Bruce Betts, chief scientist at the Planetary Society, called the Chelyabinsk incident “a wake-up call. People started taking it much more seriously after that, and the idea of planetary defense became much more accepted publicly.”
“Tunguska is the largest cosmic impact witnessed by modern humans,” said David Morrison, a planetary science researcher at NASA’s Ames Research Center. “It also is characteristic of the sort of impact we are likely to have to protect against in the future.”
In the future, a spacecraft could ram into a dangerous asteroid hard enough to change its directory. Unlike in the movie Armageddon, the spacecraft does not have to be crewed. It can be remote-controlled from Earth and hit an asteroid while it is still millions of miles away.
If a spacecraft can be sent to a potentially dangerous asteroid before it has a chance to get close to Earth, it won’t have to be all that big to knock the asteroid off course with a strategic strike. The course change will become increasingly noticeable over time.
NASA’s Planetary Defense Coordination Office currently searches for asteroids that could potentially be dangerous to Earth. It says none of the known asteroids that are more than 450 kilometers across threaten to hit Earth for at least another 100 years. However, it also warns that scientists have only found a fraction of smaller, potentially threatening asteroids like the one that killed so many people in and around Chelyabinsk.