Protecting Earth from an asteroid strike is common in science fiction, but it is also a concern for real scientists.  On September 26, the National Aeronautics and Space Administration (NASA) crashed a spaceship into an asteroid in order to alter its course. The mission, called the Double Asteroid Redirection Test (DART), was the first ever test of Earth’s planetary defenses. Although in the movies, the world is often saved by a nuclear weapon that turns the asteroid into harmless dust, a shattered asteroid is just as dangerous as a whole one. This led NASA to try a different strategy to protect the planet from future threats: altering the asteroid’s orbit.

The target of this mission was a miniature moon named Dimorphos orbiting around a larger asteroid named Didymos. Both are about 6.8 million miles away, a small distance compared to most asteroids, but still giant enough to make the DART mission possible. The ship impacted with the mini-moon at an extremely fast speed, about 14 thousand miles per hour. In theory, this would slow the movement of the asteroid by about one percent. Even this small decrease in velocity would massively change the course of the asteroid over time, implying that NASA should have the ability to redirect anything that could pose a threat to the Earth. The collision went smoothly, but at the time of writing, NASA is still uncertain how much DART affected the asteroid. Detailed observations will be taken to measure any change in the asteroid’s velocity, and the process may take several more weeks.

Dimorphous and Didymos are not threats to the human race. They are not on a path that will put them anywhere near Earth, and they would not be on a dangerous path even if the DART mission had gone wrong. The mission was a strictly scientific one. However, this does not mean that the mission was a waste of time. Brendan Crowley, a physics and astronomy teacher at CA noted, “We’ve been surprised before with big asteroids hitting the earth. And I’m not talking about the dinosaurs. In the past thirty years, there’s been at least a few that caught everybody by surprise.” While the DART mission may not have been as dramatic as science fiction, NASA taking these steps now helps to make sure that any future asteroid encounters have a good ending.