NASA DART Asteroid Impact Won’t Cause Dimorphos to Hit Earth, But Here’s What Happens If It Does

NASA’s DART spacecraft did not push the target asteroid toward Earth, but there may be other similarly sized space rocks in the path of impact with our planet – which is why the DART mission is so important.

DART crashed into the 525-foot-wide (160 meters) asteroid moon Dimorphos as planned on Monday evening (September 26), successfully demonstrating a planetary defense “kinetic strike” strategy. The dramatic collision has sparked a lot of speculation online that NASA may have inadvertently sent a harmless space rock to Earth.

Such assumptions are, of course, unfounded. Members of the mission team have calculated, and they say, that DART’s deadly dive cannot significantly change the orbit of Dimorphos and Didymus – a larger asteroid in a binary system – around the Sun. The only orbit that DART will noticeably change is the 2,560-foot (780 m) wide orbit of the Dimorphos satellite around Didymos. In fact, according to scientists, the binary nature of the Didymos system serves as a kind of protective brake against unwanted orbital changes.

“We’re moving the little guy, but the big guy is like an anchor. It’s holding it back,” Andy Cheng, chief planetary defense scientist at Johns Hopkins University’s Applied Physics Laboratory (APL) in Laurel, Md., which manages the DART mission for NASA, said at a press conference on Monday (September 26). “The orbit of the entire system around the Sun varies so little that it is difficult to measure.”

On the subject: Asteroid apocalypse: how big does a space rock need to be to end human civilization?

No threat at all

The Didymos system, while technically classified as potentially dangerous, is actually of little concern to planetary defense experts.

“The nearest distance [of the Didymos binary asteroid system] to Earth’s orbit is still on the scale of a few million miles. It’s not even a threat,” said Tom Statler, a NASA planetary scientist, at the same press conference.

Astronomers model the orbits of asteroids for centuries to come. But these orbits are shifting — for example, due to the gravitational pull of the giant planets of the solar system, such as Jupiter and Saturn. These shifts are very slow, but it is possible that one day an asteroid that is not currently a concern will become a threat.

More significant is the risk associated with asteroids that we do not yet know about. NASA and its partners estimate that only about 40% of asteroids larger than 460 feet (140 m) wide are currently known – roughly the size of Dimorphos. While no known asteroid poses a threat to Earth for the foreseeable future, space agencies around the world want to make sure they know how to prevent such a space rock from sneaking up on us. Hence the DART mission.

An artist's rendering of the DART probe's impact on the asteroid Dimorphos.

An artist’s rendering of the DART probe’s impact on the asteroid Dimorphos. (Image credit: ESA–

How much damage would an asteroid the size of Dimorphos cause if it hit Earth?

A space rock the size of Dimorphos would not have been the starting point for non-avian dinosaurs, which became extinct after colliding with an asteroid about 6 miles (10 kilometers) in diameter. However, a rock the size of Dimorphos could have caused significant destruction at the point where it collapsed.

“If a [an asteroid as big as Dimorphos] would have fallen on the City of London, windows would have been shattered all over the south east of England, and damage in [the Greater London] It will be very extreme,” Gareth Collins, professor of planetary science at Imperial College London, told airflow.”

An impact from such an asteroid would create a crater over 1 mile (1.6 km) wide and over 1,200 feet (370 m) deep, which would destroy buildings tens of miles from the epicenter. The rock is likely to explode close to the ground, Collins said, before its remnants fall to the planet’s surface and cause intense heat that will melt the ground and start fires in the area closest to the explosion site.

“If an asteroid hits the ocean, it will create very large tsunami waves,” said Collins, who created the online tool with his colleagues. (will open in a new tab)this allows researchers (and members of the public) to study asteroid collisions of various sizes. “But if this happened deep in the ocean, the waves would dissipate into waves with a fairly low amplitude before reaching the coast,” he added.

However, if such a rock were to fall into the ocean close to the shore, the impact would be devastating. And so, while the likelihood of an asteroid hitting a major city is pretty low, the planet’s defenders want to have the technology ready to repel it just in case.

How can DART help us defend against other space rocks?

There are many asteroids of various sizes, masses and compositions, and a future planetary defense mission will only have one chance to set things right. So a replica of the DART mission is not suitable for every threat striker, but the mission data will be invaluable for any future diversion campaign.

The DART experiment comes with a massive data collection effort. Hundreds of ground and space telescopes are studying the impact at this very moment, as well as a small cubesat called LICIACube that traveled to the Didymos system using DART but was launched two weeks ago to take pictures of the impact and its aftermath.

And in 2024, the European Space Agency will launch the Hera mission, which will take additional measurements of Didymos and Dimorphos, including X-rays of the interior of rocks, to learn as much as possible about asteroids and the mechanics of DART. influence. By using this data in sophisticated computer models, scientists and engineers will be able to accurately calculate the behavior of other asteroids and perhaps one day design a true deflection mission with the best chance of success.

Follow Tereza Pultarova on Twitter @TerezaPultarova. Follow us on Twitter @Spacedotcom and on Facebook.

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