NASA Probe Ready To Slam Into An Asteroid This Month

On Sept. 26, the Double Asteroid Redirection Test (DART) mission will slam headfirst into a small asteroid in the name of planetary defense. “[S]cientists hope that should a dangerous asteroid threaten the planet in the future, a mission like DART could avert the disaster,” reports Space.com. From the report: The theory goes that if scientists ever detected an asteroid on a collision course with Earth, an impactor probe could realign the orbit of the space rock, ensuring that it crossed Earth’s path when our planet was a safe distance away. But scientists don’t want to be working only from theory if the situation arises. That’s where DART’s dramatic destruction comes into play. The spacecraft will slam into a small asteroid called Dimorphos, which like clockwork orbits a larger near-Earth asteroid called Didymos every 11 hours and 55 minutes. (Neither asteroid poses any threat to Earth, and DART won’t change that.) The DART impact should adjust the orbit of Dimorphos, cutting its circuit by perhaps 10 minutes.

Scientists on Earth will be spending weeks after the impact measuring the actual change in the moonlet’s orbit to compare with their predictions. The work will refine scientists’ understanding of how asteroids respond to impactors and help to tune any future missions to the necessary amount of orbital change. “This isn’t just a one-off event,” Nancy Chabot, the DART coordination lead at the Johns Hopkins University’s Applied Physics Laboratory in Maryland, which runs the mission, said during the news conference. “We want to know what happened to Dimorphos, but more important, we want to understand what that means for potentially applying this technique in the future.”

While the stakes are low compared to any scenario that would motivate a real asteroid-deflecting mission, the difficulty is the same. “This is incredibly challenging,” Evan Smith, the deputy mission system engineer, said during the news conference, noting that the spacecraft will only be able to see Dimorphos itself about an hour and a half before impact. “This is a par-one course, so we’re going in for the hit this time.” And if something doesn’t go according to plan? Mission personnel are pretty confident that, as long as the spacecraft hits its target, there should be something to see. “If DART collides with Dimorphos and then you don’t see any orbital period change, this would be exceptionally surprising,” Chabot said. “Just the amount of momentum that DART is bringing in on its own from the weight of the spacecraft slamming into Dimorphos is enough to shift its orbit in a measurable way.”