Last September, NASA’s Double Asteroid Redirection Test (DART) spacecraft crashed into an asteroid, deliberately altering the trajectory of rocks through space in the first test of planetary defenses. Now scientists have disassembled the crash and its aftermath, and learned just how successful humanity’s punch in space really was.
A dart the size of a golf cart collided with an asteroid the size of a pyramid called Demorphos. The impact shrunk the asteroid’s orbit around another cosmic rock — Demorphos now completes its orbit 33 minutes faster than it did before the impact. NatureThis means that if a dangerous asteroid is detected heading towards Earth, a mission that hits it can likely be steered away from the planet.
DART’s success has been reported before.Currently 5 studies Nature Describes the final moments of the crash and its effect on the asteroid. One group combined data on the spacecraft’s trajectory with photographs of the asteroid’s surface just before impact. As DART hurtled toward Dimorphos at more than 6 kilometers per second, the first part to hit was one of its solar panels, which slammed into a 6.5-meter-wide rock. A few microseconds later, the spacecraft’s body hit the rock face next to the rock, shattering her $330 million DART into pieces.
The impact ejected at least 1 million kilograms of rock from Demorphos’ 4.3 billion kilogram mass. The debris formed a tail that stretched for tens of thousands of kilometers behind the asteroid. Over the course of several weeks, various telescopes monitored the tail as it migrated and evolved under the pressure of the sun’s rays. The Hubble Space Telescope detected her second tail, which disappeared 18 days after the collision.
Dimorphos is 151 meters wide and orbits the larger asteroid Didymos. NASA’s goal was to find changes by astronomers altering Dimorphus’ orbit to monitor the pair’s brightness over time using ground-based telescopes. Neither asteroid is and will never be a threat to Earth.
Images taken by DART as it passed by Dimorphos on September 26 show that the asteroid looks like a rocky egg. It looks like a loose pile of debris barely held on by gravity — its surface would probably shatter spectacularly when a DART hits it.
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Carolyn Ernst, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, says the more detailed findings will help researchers understand why the impact was so successful in pushing the asteroid away. says it helps.
One factor is that the spacecraft hit about 25 meters from the asteroid’s center, where the force of impact was maximum. Another is that a large amount of the asteroid’s debris flew outwards due to the impact. The recoil from this force pushed the asteroid further out of its previous orbit. The researchers estimate that this debris blast caused the Dimorphos-added momentum to be nearly four times greater than the momentum imparted by DART.
Although NASA has only demonstrated the technique on one asteroid, the researchers say the results could be broadly applicable to future disasters. “This means we can quickly design a mission to deflect an asteroid if there is a threat, and we know that this is very likely to be effective,” he said of his SETI Institute in Mountain View, Calif. says Franck Marchis. He is also Chief Scientific Officer of telescope manufacturer He Unistellar in Marseille.
“Thirty years ago, if you had asked me, ‘Are you sure we won’t be wiped out by a giant killer asteroid for a week starting next Tuesday?’ I would have had to say no.” adds Tom Statler, a DART program scientist at NASA headquarters in Washington, DC. Now that astronomers have surveyed the skies and identified nearly every dangerous asteroid, and DART has been shown to work, he asked, “When something new is found, what should we do about it?” I understand,” he says.
Researchers continue to explore the DART data to learn more about the physics, chemistry and geology of both Dimorphus and Didymo. This work is being done with the help of a network of amateur astronomers co-led by Marquis. Network members observed the asteroid with telescopes before, during, and after impact. They found that the rock appeared noticeably reddish shortly after the spacecraft hit it.
The subsequent color change to blue was observed at NASA’s infrared ray in Hawaii, as reported by Christina Thomas, a planetary scientist at Northern Arizona University in Flagstaff, at the American Geophysical Union’s December meeting. Discovered by a telescope facility. “We think this is likely a lot of material being dumped from Dimorphus,” she says. A few hours later, the asteroid briefly appeared blue.
Scientists will be able to take a closer look at the aftermath of the collision in late 2026, when a European Space Agency spacecraft named Hera arrives at Demorphos. Researchers want to know what the impact crater left by the DART smash looks like. In the meantime, detailed scientific observations will continue for several weeks until Didymus and Dimorphus move away from Earth and are no longer visible to most telescopes, then move behind the Sun.
“It’s really exciting to still see the evolution of what’s going on,” says Thomas.
This article is reproduced with permission and was first published on March 1, 2023.
