3 grains of asteroid dust store its secrets

 Despite their small size, and being smaller than the thickness of a hair, three grains of dust carry a history that extends billions of years to an asteroid, and store many of its secrets. The three particles from the Itokawa asteroid revealed that this type of space object is much older than previously thought, and is much more solid.

This entails a review of plans in place to avoid a collision with the planet, according to a study published Monday in the "Proceedings" journal of the US National Academy of Sciences. The three samples were brought in 2005 from the asteroid, when it was about 300 million km from Earth. Five years later, the Japanese space probe "Hayabusa" transported these samples to Earth, along with hundreds of other particles from Itokawa.

Professor at the Faculty of Earth and Planetary Sciences at Australian Curtin University Fred Jordan sought to know the age of Itokawa, a type of asteroid described as having a "loose mass". It is caused by the aggregation of fragments of a compact asteroid that was shattered by the impact.

It is known that compact asteroids have a lifetime of a few hundred million years, and that they are gradually eroding due to collisions with other asteroids. Loose-mass asteroids, such as Itokawa, have a very different structure, containing a variety of rocks, dust, pebbles, and even voids, held together by a small effect of gravity.

Professor Jordan likened it to "a giant pillow in space, and pillows are capable of absorbing shocks." To find out to what degree, the team analyzed the crystal structure of the samples, looking for distortions from the collision that created Itokawa, and also dated them.

The researchers concluded that Itokawa was formed after a collision that occurred at least 4.2 billion years ago, which is approximately the age of Earth (4.5 billion years), but more importantly, it is ten times older than the age of homogeneous asteroids of similar size.

Because of the importance of the age of this asteroid, Jordan is convinced that some of his colleagues will not believe him. The study indicated that the flexibility of this type of space object in the face of collisions leads to the belief that it may be much more than previously thought.

The result of this, the geochemist said, is the adaptation of methods of protection from Earth's collision with this type of asteroid. The "Dart" experiment to deflect an asteroid, which was successfully conducted by the US space agency (NASA) last year, shows that this is possible with an object like Itokawa, according to the scientist. But this would require much greater force to be applied to it, for example with a nuclear warhead, so that "the shock wave would be able to deflect the asteroid from its trajectory".