Crashing into an asteroid... for science!
Credit: NASA, Johns Hopkins Applied Physics Lab
It’s a popular science fiction trope: an asteroid on a collision course with Earth threatens to drive humanity to extinction. At the last minute, a hero flies into space, stops the asteroid, and saves all life on Earth–sometimes sacrificing their own life in the process. Stories like these make for great movies, but they might not be as far from reality as they seem. Every day, Earth is bombarded with asteroids. Mostly, these asteroids are tiny and burn up in the atmosphere, creating brilliant shooting stars in the night sky. But what if a bigger asteroid – MUCH bigger – were going to hit our planet? Would we actually be able to stop it?
Meet DART, the real-life hero that could be humanity’s ticket out of an asteroid Armageddon. DART, short for the Double Asteroid Redirection Test, is a NASA satellite on a mission to test whether we have the technology to defend our planet against asteroid attackers. Unlike the movies, DART won’t try to destroy the asteroid with lasers or nuclear explosions. Instead, the satellite is a “kinetic impactor,” meaning it will attempt to deflect the asteroid by crashing into it at over 14,000 miles per hour. This collision will only move the asteroid slightly, but a careful nudge at the right time will change the asteroid’s path forever. If done correctly, this technique could turn a direct hit into a million-mile miss.
DART will test this asteroid deflection technique on a near-Earth asteroid named Didymos. For comparison, Didymos is much smaller than the asteroid that killed the dinosaurs, but still large enough that it would cause serious damage if it ever hit Earth. Fortunately, astronomers are certain that Didymos will never cross paths with Earth, even after a course-correction from DART, which makes it the perfect target for this demonstration. Just like Earth, Didymos has a smaller asteroid that orbits it like a moon. DART will crash into this “moon,” changing its speed slightly. Because Didymos is pulled by its mini-moon’s gravity, this push on the asteroid-moon will also pull Didymos off-course. Even a minor adjustment in the asteroid’s direction will quickly snowball into a much larger deflection. In the years following the collision, astronomers will monitor Didymos and study its change in trajectory to get a better sense of what it takes to deflect an asteroid.
Through this mission, DART will teach us the best way to keep Earth safe from dangerous asteroids and demonstrate that we are able to defend our planet if necessary. One day, the science fiction stories about looming asteroid apocalypse could become a reality. If day ever comes, humanity will be ready to defend itself thanks in part to DART’s sacrifice.
Andrew Shumway is an astrobiologist and planetary scientist who is fascinated by the role of water on Mars. His experiments simulate the cold, dry conditions of Mars’ surface to study how water forms in extreme environments.