How three dust particles reveal the secrets of an asteroid
Samples from Itokawa returned to Earth in 2010 after being collected by the Hayabusa probe.
The grains are tiny. No, really tiny. Smaller than the diameter of a hair. But they hold billions of years of history that reveal some of the secrets of asteroids.
The three tiny particles from an asteroid called Itokawa show that some of these space rocks are much older than previously thought and are much tougher.
And that could mean we need bolder ways to prevent catastrophic collisions with Earth, according to research published Tuesday.
The three samples were collected in 2005 on the peanut-shaped Itokawa, some 300 million kilometers from Earth.
It took the Japanese spacecraft Hayabusa five years to bring them back to Earth, along with hundreds of other particles from Itokawa, and scientists have been analyzing them ever since for clues.
Fred Jourdan, a professor at Curtin University’s School of Earth and Planetary Sciences, wanted to see what the spots could reveal about the age of rubble-pile asteroids like Itokawa.
These form when solid asteroids collide and the resulting fragments come together to form new structures.
Solid asteroids are believed to have a lifespan of hundreds of millions of years and are gradually crushed by constant collisions.
But rubble-pile asteroids have a very different structure, made up of rocks, dust, pebbles and a vacuum, and held together by the gravitational pull of their various components.
“It’s like a giant space cushion, and cushions are good at absorbing shock,” Jourdan said.
To find out just how much, the team analyzed the crystal structures of the samples, looking for deformations caused by the impact that created Itokawa.
She also dated the samples by measuring the decay of potassium into argon.
The methods suggest Itokawa was formed by an asteroid collision at least 4.2 billion years ago, ten times older than expected for solid asteroids of similar size.
“We were really surprised,” Jourdan said.
“I mean it’s really, really old, and I’m sure some of my colleagues won’t even believe it.”
Rubble-pile asteroids are so resilient to the constant shocks they experience that they are likely far more abundant than previously thought, concludes the research published in the journal Proceedings of the National Academy of Sciences.
According to Jourdan, that could mean we need to find new ways to tackle those asteroids that are at risk of colliding with Earth.
NASA’s recent DART test showed that asteroids like Itokawa can be diverted from their path, but this would likely require a delay of several years.
An asteroid weeks away from colliding with Earth would require a different approach, and Jourdan believes a nuclear explosion might be necessary.
This is not an “Armageddon” type explosion, he hastens to add, in reference to the 1998 sci-fi film.
“The shock wave should push the asteroid off course.”
It’s a far-reaching conclusion to draw from such small specks of dust, but each particle is analyzed at the atomic level.
“We can get big stories like that out of (something) very, very small, because these machines, what they do is measure and count atoms,” Jourdan said. .
“Each bean has its own story to tell”.