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NASA DART test hit its asteroid target — but that’s just the beginning

Published: Friday, September 30, 2022 - 12:04pm
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On Monday, NASA’s Double Asteroid Redirection Test (DART) spacecraft struck Dimorphos, a small asteroid circling a larger one, Didymos, 7 million miles away.

“We’ve been working on this for years, and to see it really come to fruition and to have it be so phenomenally on track with our predictions was absolutely fantastic,” said Cristina Thomas, a planetary scientist at Northern Arizona University who leads the mission's observation team.

If the test collision slowed Dimorphos, it would bolster the hope that such an impact could defend the Earth from dangerous asteroids or comets.

What’s more, studying how DART’s impact altered the surface of the 530-foot-wide moonlet and analyzing the material kicked up on impact will offer valuable clues to the rubble-pile’s composition.

DART’s final look at the asteroid moonlet Dimorphos before impact. NASA/Johns Hopkins APL

“There’s a lot about the physical properties of asteroids that is currently still under investigation, and it’s really, really interesting because the physics that we see when we visit these bodies is very different than the physics on our planet, largely because of gravity and the way it's held together,” said Thomas.

Recent missions to orbit and sample asteroids have only increased that mystery. The OSIRIS-Rex mission found that the asteroid Bennu, rather than clumping together cohesively as expected, was as loosely packed as a dust bunny and held together largely by electrostatic charge — essentially, static cling.

“The canister that was designed to pick up material from the surface actually sank in farther than they were expecting,” said Thomas.

But before ground-based telescopes can reveal more about Dimorphos, they must literally wait for the dust to settle.

“We know that the impactor should have shortened that orbital period. The big question right now is, by how much?” said Thomas.

If all went to plan, the 14,000-mile-per-hour impact will have shortened Dimorphos’s orbit around Didymos by 1%, or around 10 minutes of orbital time.

The Lowell Discovery Telescope, located near the northern Arizona community of Happy Jack, will play a key role in making those observations.

“We're hoping that, in a couple of days, the activity from the ejecta will have gone down to a level that will allow us to get back on the sky with our telescopes and really start to study the orbital period in great detail,” said Thomas.