Space dust from 4.2 billion-year-old asteroid could be key to preventing catastrophic collision with Earth

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Scientists suggest that tiny specks of dust from a “giant space cushion” almost as old as the solar system could provide new clues to avoid catastrophic asteroid collisions with Earth.

Three tiny dust particles – smaller than the diameter of a hair – collected from the 500-meter-high asteroid known as Itokawa show that some of these space rocks are much older and harder than previously thought.

The peanut-shaped Itokawa is classified as a potentially hazardous asteroid that could come dangerously close to Earth and cause significant damage if it collided.

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A study published in the Proceedings of the National Academy of Sciences found that Itokawa formed more than 4.2 billion years ago, making it 10 times older than solid asteroids of similar size. For comparison, the solar system is 4.57 billion years old.

Itokawa is a debris asteroid that is formed when solid asteroids collide and the resulting fragments assemble into new structures. They are composed of rock, dust, pebbles and void, and are held together by the gravitational pull of their various constituents.

Solid asteroids are thought to have lifetimes of several hundred million years and are gradually destroyed by constant collisions.

“This long asteroid survival time is attributed to the shock-absorbing nature of the debris and suggests that debris piles are difficult to destroy once they have formed,” the study authors wrote.

“We were really surprised,” said Prof. Fred Jourdan of Curtin University’s School of Earth and Planetary Sciences, first author of the study. “It’s really, really old and I’m sure some of my colleagues won’t even believe it.”

“It’s like a giant space cushion, and the cushions are good at absorbing shocks,” Jourdan told AFP.

Debris-pile asteroids are so resilient to the constant impacts they come in contact with that there are likely to be many more of them than previously assumed. That could mean we need new ways to deal with such asteroids on a collision course with Earth, Jourdan said.

NASA’s recent Dart test showed that asteroids like Itokawa could be swerved off course, but it would likely take several years of implementation.

An asteroid just weeks away from colliding with Earth would require a different approach, and Jourdan says a nuclear blast may be needed if the asteroid is detected too late to bounce off a direct impact.

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“It’s not like Armageddon,” he says, referring to the 1998 science-fiction film. “The shock wave should push the asteroid out of the way [without destroying it]”.

Drawing far-reaching conclusions from such tiny dust particles, however, is an analysis of each particle at the atomic level.

The team analyzed the crystal structures in the samples, looking for deformations caused by the impact that created Itokawa. They dated the samples by measuring the decay of potassium into argon.

“We can bring out such great stories [something] very, very small because these machines measure and count atoms,” Jourdan said. “Every seed has a story to tell.”

The three Itokawa dust samples were originally collected by the Japanese Space Agency’s Hayabusa 1 probe in 2005.

The samples were returned to Earth five years later. Since then, scientists have been analyzing them along with hundreds of other Itokawa particles for clues.

– From AFP

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