(Tokyo) The grains are tiny, smaller than the thickness of a hair, but they hold billions of years of history of an asteroid’s secrets.
Posted at 3:09pm
Sara HUSSEIN Agence France-Presse
The three particles from the asteroid Itokawa showed that this type of space object is much older than previously thought and much harder.
That would involve revising plans to avoid a collision with Earth, according to a study published Monday in the journal Proceedings of the US National Academy of Sciences.
The three samples were recovered from the asteroid in 2005 when it was about 300 million kilometers from Earth. It took the Japanese Hayabusa spacecraft five years to return them from Itokawa to the blue planet, along with hundreds of other particles.
Fred Jourdan, a professor in the College of Earth and Planetary Sciences at Australia’s Curtin University, was trying to figure out the age of Itokawa, a type of asteroid said to have a “loose cluster”.
It results from piecing together the fragments of a monolith asteroid that has been pulverized by a shock.
Monolithic asteroids are said to have lifetimes of a few hundred million years and are gradually eroded by collisions with other asteroids.
The loosely clustered asteroid, like Itokawa, has a very different structure. Featuring a motley collection of rocks, dust, gravel and even vacuum held together by a simple effect of gravity.
‘It’s like a giant pillow in space, and pillows absorb shock well,’ notes Professor Jourdan.
To find out how much, the team analyzed the crystal structure of the samples, looking for deformations from the impact Itokawa generated. And dated her too.
The conclusion is that Itokawa formed after a collision at least 4.2 billion years ago, almost as old as Earth (4.5 billion years) but importantly ten times older than the ages of similar-sized monolithic asteroids.
An age so venerable that Fred Jourdan is “convinced” some of his peers “won’t believe it.”
The resilience of this type of space object to collision is so great that, according to the study, there should be many more of them than previously thought.
With the consequence of adapting the methods of protecting against a collision of the Earth by this type of asteroid, the geochemist notes.
According to the scientist, the DART experiment to deflect an asteroid, which was successfully carried out by NASA last year, shows that this is possible with an object like Itokawa. But a much greater force would have to be applied to it, for example with a nuclear warhead, so that “the shock wave deflects the asteroid from its orbit”.