The Dimorphos asteroid
Last week, this column covered headlines about troubles being experienced by NASA with the International Space Station. This week, I want to describe a “recent” success: the DART (Double Asteroid Redirection Test) mission.
Over the past few decades, astronomers have identified at least 2,200 asteroids (wider than 460 feet) orbiting around the Sun and coming within 5 million miles of Earth’s orbit.
Recognizing the hazardous potential these large rocks present to earthlings and wanting to test the feasibility of redirecting one if it did threaten the Earth, in November 2021, NASA launched a rocket containing a mini-fridge-sized space probe, a reconnaissance camera unit, and one of Carl Sagan’s space kites for carrying the probe and camera hurtling towards Dimorphos, a 525-foot wide asteroid (“moonlet”) orbiting Didymos, a half-mile wide asteroid circumnavigating the Sun every 2.11 years.
Almost a year later, in September 2022, shortly after dropping off the camera to document the probe’s impact, the probe hit Dimorphos solidly while traveling at 4 miles a second (roughly 15,000 mph). As a result, 1% of the asteroid’s mass sprayed into space and quickly formed a long tail visible by telescopes on Earth and in space. Yes, you can see a movie of what the Hubble telescope captured at science.nasa.gov/missions/hubble/hubble-captures-movie-of-dart-asteroid-impact-debris).
More importantly, the test shortened Dimorphos’ orbit around Didymos by 32 minutes, more than five times as much as NASA claimed would validate the technique’s ability to alter an asteroid’s trajectory.
Thanks, NASA. For only $324 million, our world can now sleep a little more soundly.