Three motes of dust reveal the secrets of an asteroid – Science et Avenir

The grains are tiny, less than the thickness of a hair, but they contain billions of years of history of the secrets of the asteroid.

Three particles of the Itokawa asteroid showed that this type of space object is much older than thought and much harder.

According to a study published on Monday in the journal Proceedings of the US National Academy of Sciences, this will require a revision of plans to prevent a collision with the Earth.

Three samples were recovered in 2005 from the asteroid when it was about 300 million kilometers from Earth. It took the Japanese space probe Hayabusa five years to return them to the blue planet, along with hundreds of other particles from Itokawa.

Fred Jordan, a professor at the Australian Curtin University College of Earth and Planetary Sciences, has been trying to figure out the age of Itokawa, a type of asteroid said to have a “loose agglomerate”.

It arises as a result of the assembly of fragments of a monolithic asteroid, which was torn apart by a shock wave.

Monolithic asteroids are said to live for several hundred million years and are gradually destroyed by collisions with other asteroids.

A loose cluster asteroid like Itokawa has a completely different structure. With a motley collection of rocks, dust, gravel, and even vacuum held together by the simple act of gravity.

“It’s like a giant pillow in space, and the pillows are good at absorbing shock,” says Prof. Jourdan.

To find out just how bad, the team analyzed the crystal structure of the samples, looking for deformations from the impact that Itokawa had created. Also date them.

The conclusion is that Itokawa was formed after an impact that occurred at least 4.2 billion years ago, which is almost the same age as the Earth (4.5 billion years), but primarily ten times older than similarly sized monolithic asteroids.

The age is so respectable that Fred Jourdan is “convinced” that some of his colleagues “won’t believe him”.

According to the study, the resistance of a space object of this type to collisions is such that there should be much more of them than previously thought.

The consequence of this is the adaptation of methods of protection against collisions with the Earth of such asteroids, the geochemist notes.

The DART asteroid deflection experiment successfully conducted by NASA last year shows that this is possible with an object like Itokawa, the scientist said. But this would require the application of a much greater force to it, for example, a nuclear warhead, so that “the shock wave deflected the asteroid from the course.”

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