Asteroids made of “debris” can be very, very hard to destroy, astronomers say
While it’s a common premise in science fiction, the prospect of a large asteroid hitting Earth isn’t fiction at all, but rather a guarantee. Asteroids with extinction events occur periodically, just like the tides or the full moon; just ask the dinosaurs. This is why the National Aeronautics and Space Administration (NASA) spent so much time and money on the Double Asteroid Redirection Test (DART) missionwho successfully tested our ability to create a asteroid of hitting 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 Australia’s Curtin University, debris asteroids are more durable (and more common) than previously thought, potentially changing the way scientists think about possible planetary defenses. Mess asteroids are a particular type of asteroid that, true to their name, consists of smaller debris the size of boulders and rocks that have fused together under the influence of gravity. These types of asteroids are notoriously diffuse compared to bedrock.
But if you thought that these pieces of rubble were weak and easy to break due to their composition, you would be wrong.
In the study, Jourdan and his colleagues looked at the origin, composition and durability of rubble asteroids thanks to the Japan Space Agency’s (JAXA) Hayabusa 1 probe return mission.
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As you may recall, in 2005 JAXA collected samples from an asteroid called Itokawa – and despite numerous misadventures to return them 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 whether the returned particles from Itokawa had previously impacted 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.
“Asteroids are usually thought of as a large piece of solid rock, but not all of them are like that — some are called rubble piles because they are rocks, boulders and pebbles that have clumped together, but there are a lot of empty spaces between those rocks and that makes extra empty space they’re shock absorbing,” Jourdan told Salon via email. “Mess asteroids like Itokawa are like a giant space cushion.”
Jourdan further explained that pillows are soft because they contain a lot of air.
“So it’s good to absorb shock, right?” said Jourdan. “The same goes for debris-packed asteroids. They’re just good at absorbing shock.”
This new discovery could be why the team of researchers found that Itokawa is so old – an estimated 4.2 billion years old, which is almost as old as our own solar system.
“We were surprised,” Jourdan said of the asteroid’s age. “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 — yet Itokawa survived for more than 4.2 billion years; much longer than we thought. would.”
However, Jourdan said the main implication of his research is that rubble asteroids are “resistant to bombardment.” While that may sound like we Earthlings are doomed in terms of planetary defense, he said we can “use that to our advantage.”
“So what we’re suggesting in our study is that we should explore the possibility of detonating 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 and eject a small asteroid called Dimorphos. Although the mission was a resounding success, Jourdan said: “The problem is that it is necessary to detect the asteroids very early, as the pressure will be very small.”
“So if the asteroid starts to get pushed by kinetic impact, say three years before it collides with Earth, no big deal; 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’re suggesting in our study is that we should investigate the possibility of detonating 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 DART.”
Jourdan said the fact that mess asteroids are so durable means the purpose of the blast wouldn’t be to destroy them, but just to shift their orbit so they wouldn’t hit Earth.
“Exploding an asteroid is really not the way to go, because all the debris would rain down and cause similar devastation,” he said.
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