NASA said Tuesday it had successfully deflected an asteroid in a historic test of humanity’s ability to stop an incoming space object from destroying life on Earth. The refrigerator-sized Double Asteroid Redirection Test (DART) impactor intentionally slammed into the lunar asteroid Dimorphos on Sept. 26, pushing it into a smaller, faster orbit around its big brother Didymos, NASA chief Bill Nelson said. “DART shortened the orbit from 11 hours 55 minutes to 11 hours 23 minutes,” he said. Dimorphos’ orbital period acceleration of 32 minutes exceeded NASA’s own expectation of 10 minutes. “We showed the world that NASA is serious about being the defender of this planet,” Nelson added.
A pair of asteroids orbit our Sun every 2.1 years and pose no threat to our planet. But they are ideal for studying the “kinetic impact” method of planetary defense in case a truly approaching object is ever detected. DART’s success as a proof of concept made science fiction a reality – especially in movies like “Armageddon” and “Don’t Look Up.” Astronomers were delighted by the stunning images of matter spread thousands of miles in the wake of the impact – images collected by ground-based and space-based telescopes, as well as a mini-satellite that traveled to the zone using DART.
Pseudocomet
Dimorphos, which is 530 feet (160 meters) in diameter, or roughly the size of the Great Pyramid of Egypt, has been transformed into an artificial comet thanks to its temporary new tail. But quantifying how well the test worked required analyzing light patterns from ground-based telescopes, which took several weeks to show. The binary asteroid system, which was about 6.8 million miles (11 million kilometers) from Earth when it impacted, is only visible from Earth as a single dot.
Ahead of the test, NASA scientists said the results of the experiment would reveal whether the asteroid is a solid rock or rather a “junk pile” of boulders bound together by gravity. If the asteroid is more solid, the momentum carried by the spacecraft will be limited. But if it is “fluffy” and significant mass is pushed at high speed in the opposite direction to the impact, additional reinforcement will occur.
Dimorphos, which had never been actually photographed before, appeared as a bright spot about an hour before impact. Its ovoid shape and rocky, boulder-strewn surface finally emerged in the last few moments as DART hurtled toward it at roughly 14,000 miles per hour.
Mass extinction
Very few of the billions of asteroids and comets in our solar system are considered potentially dangerous to our planet, and none are expected in the next hundred years or so. But wait long enough and it will. For example, the geological record shows that 66 million years ago, a six-mile-wide asteroid hit Earth and plunged the world into a long winter that led to the mass extinction of the dinosaurs along with 75 percent of all species.
An asteroid the size of Dimorphos, on the other hand, would only cause a regional impact such as devastation to a city. Kinetic impact by spaceship is only one way to defend the planet, albeit the only way possible with current technology. If an approaching object were detected in time, a spacecraft could be sent to fly alongside it long enough to deflect its trajectory using the ship’s gravitational force, creating a so-called gravity tractor.
Another option would be to launch nuclear explosives to redirect or destroy the asteroid. NASA believes the best way to deploy such weapons would be from a distance, delivering the force without blowing the asteroid to pieces, which could further threaten Earth.
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