Although it is a common premise in science fiction, the possibility of a large asteroid crashing into Earth is not fiction at all, but rather a guarantee. Asteroids in extinction events occur periodically, just like tides or a full moon; just ask the dinosaurs That’s why the National Aeronautics and Space Administration (NASA) spent so much time and money on the Double Asteroid Redirection Test. (DART) missionwhich successfully tested our ability to deflect a asteroid to hit the Earth. That mission was a success and (apparently) suggests that asteroids are not as dangerous as one might think.
But what if the asteroid in question was nearly indestructible?
According to new research published in the Proceedings of the National Academy of Sciences (PNAS), led by planetary scientist Fred Jourdan of Curtin University in Australia, debris pile asteroids are more durable (and common) than previously thought, possibly changing the way scientists think on possible planetary defense measures. Rubble-pile asteroids are a particular type of asteroid that, true to their name, consist of smaller pieces of debris the size of boulders and rocks that have coalesced under the influence of gravity. These types of asteroids are notoriously diffuse compared to solid rock.
However, if you thought that these rubble piles were, by virtue of their composition, weak and easily broken, you would be wrong.
In the study, Jourdan and his colleagues analyzed the origin, composition and durability of rubble-pile asteroids thanks to the sample return mission of the Hayabusa 1 probe of the Japanese Space Agency (JAXA).
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As you may recall, JAXA collected samples from an asteroid called Itokawa in 2005, and despite numerous setbacks in bringing them back to Earth, they succeeded in 2010. More than a decade later, using a technique called backscattered electron diffraction, Jourdan and his team were able to determine if the particles returned from Itokawa had previously been impacted in space. Through this process of scanning the surface of the particles, the researchers concluded that these asteroids are nearly indestructible, thanks to a unique “cushion”-like feature.
“Usually, asteroids are thought of as being one big chunk of solid rock, but not all are like that: some are called rubble piles because they’re clumped rocks, boulders, and pebbles, but there are lots of empty spaces between those rocks and that extra void space makes them shock absorbent,” Jourdan told Salon via email. “Rubble-pile asteroids like Itokawa are like a giant space cushion.”
Jourdan further explained that the cushions are soft because they have a lot of trapped air.
“So it’s good to absorb the shock, right?” Jordan said. “The same goes for rubble-pile asteroids, they’re good at absorbing impact.”
This new discovery could be the reason why the team of researchers discovered that Itokawa is so old: it is estimated to be 4.2 billion years old, which is about the same age as our own solar system.
“We were surprised,” Jourdan said of the age of the asteroid. “Most models predict that an asteroid with a size of a few hundred meters to a few kilometers should survive environmental bombardment in the asteroid belt for a few hundred million years; however, Itokawa survived more than 4.2 billion. of years, much longer than we thought. it would.”
However, Jourdan said the most important implication of his research is that Rubble Pile asteroids are “resilient to bombardment.” While that may seem like we Earthlings are doomed in terms of planetary defense, he said we can “use it to our advantage.”
“So what we suggest in our study is that we should explore the possibility of setting off a nuclear device very close to the asteroid.”
when it came to the DART mission 2022, NASA sent a 1,320-pound spacecraft to crash into a small asteroid called Dimorphos and knock it out of orbit. While the mission was a resounding success, Jourdan said, “The problem is that it requires detecting the asteroids early on, as the momentum will be very small.”
“So if the asteroid starts to get pushed around by a kinetic impact, say three years before it hits Earth, there’s no problem; DART-like devices can do it,” Jourdan said. “But what if we don’t have enough time? What if we suddenly find out that an asteroid will hit Earth in 3 months? What do we do?”
This is where Jourdan’s new research comes into play.
“So what we suggest in our study is that we should explore the possibility of setting off a nuclear device very close to the asteroid,” Jourdan said. “Why? Because the shock wave would be much more energetic than small kinetic impactors like DARTs.”
Jourdan said that the fact that rubble-pile asteroids are so durable means that the goal of the explosion would not be to destroy them, but simply to push their trajectory away from hitting Earth.
“An asteroid explosion really isn’t the way to go, as all the debris would rain down and cause similar devastation,” he said.
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