Tiny specks of dust from a “giant space pad” almost as old as the solar system could provide new clues about how to avoid a catastrophic asteroid collision with Earth, research suggests.
Three tiny dust grains — smaller than the diameter of a human hair — collected from a 500-meter-long asteroid called Itokawa suggest some of these space rocks are much older and harder than previously thought many.
The peanut-shaped Itokawa is classified as a potentially hazardous asteroid that could veer dangerously toward Earth and cause major damage on impact.
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 the same size. By comparison, the solar system is 4.57 billion years old.
Itokawa is a rubblepile asteroid that forms when solid asteroids collide and the resulting fragments assemble into new structures. They consist of rocks, dust, pebbles, and a void held together by the gravitational pull of their various constituents.
Solid asteroids are thought to have a lifespan of hundreds of millions of years and are gradually crushed in constant collisions.
“The asteroid’s long survival time is attributed to the shock-absorbing properties of the rubble pile material, suggesting that the rubble pile is difficult to destroy once formed,” the study’s authors wrote.
“We were really surprised,” said the study’s lead author, Professor Fred Jourdan from Curtin University’s School of Earth and Planetary Sciences. “It’s really, really old, and I’m sure some of my colleagues wouldn’t even believe it.”
“It’s like a giant space cushion, and the cushion absorbs the impact really well,” Jordan told AFP.
Rubblepile asteroids are so resilient to the constant impacts they face that they may be much more numerous than previously assumed. That could mean we need new ways to deal with such asteroids colliding with Earth, Jourdan said.
NASA’s recent Dart tests show that asteroids like Itokawa can be pushed out of orbit, but that could take years to prepare.
Asteroids that are just weeks away from colliding with Earth will require a different approach, and Jourdan believes a nuclear explosion may be required if the asteroid is discovered too late for a direct impact deflection.
“It’s not ‘end of the world’ style,” he said, referring to the 1998 sci-fi flick. “The shock wave should have pushed the asteroid away [without destroying it]”
The conclusions drawn from such tiny dust particles are profound, but each particle is analyzed at the atomic level.
The team analyzed the crystal structures in the samples, looking for deformations caused by the impact that caused Itokawa. They dated the samples by measuring the decay of potassium to argon.
“We can get big stories like this out of [something] Very, very small, because those machines, what they’re doing, are measuring and counting atoms,” Jourdan said. “Every grain of grain has its own story to tell. “
The three Itokawa dust samples were originally collected in 2005 by Japan’s space agency’s Hayabusa-1 probe.
Five years later, the samples were returned to Earth. Since then, scientists have been analyzing them, and hundreds of other particles from Itokawa, for clues.