Asteroid Itokawa, which has been recognized as potentially dangerous to Earth, will be difficult to destroy, according to a new study analyzing dust particles collected from its surface.

Measuring 330 meters across, Itokawa is the first ever asteroid to be sampled by a space mission. The Japan Aerospace Exploration Agency launched its Hayabusa-1 probe in 2003 to study Itokawa, and seven years later it managed to return to Earth about a milligram of material taken from the surface of the asteroid.

Now, an international team of researchers led by Curtin University in Australia has studied three dust particles from this sample to assess the age and character of Itokawa. The argon dating method showed that the asteroid is older than 4.2 billion years and has a cushion-like structure. The team discovered that Itokawa is older and stronger than previously thought.

“Unlike monolithic asteroids, Itokawa is not a single lump of rock, but belongs to the rubble pile family which means it’s entirely made of loose boulders and rocks, with almost half of it being empty space,” said Fred Jourdan, author of the study, published in the Proceedings of the National Academy of Sciences journal, of and a geochemistry professor at Curtin University.

Due to the gaps, debris asteroids absorb the shock wave from collisions well.

“We found that Itokawa is like a giant space cushion, and very hard to destroy,” Jourdan added. Itokawa was originally formed from a monolithic ancient asteroid that fractured into pieces after a violent collision. Bits of leftover rock and dust coalesced into a rubble pile under gravitational forces to create Itokawa.

“Now that we have found they can survive in the solar system for almost its entire history, they must be more abundant in the asteroid belt than previously thought, so there is more chance that if a big asteroid is hurtling toward Earth, it will be a rubble pile,” said Nick Timms, co-author of the paper and geology professor also from Curtin University.

He believes that a more detailed study of these types of space rocks will help space agencies around the world develop strategies to prevent potential collisions.