(ORDO NEWS) — After examining samples of the asteroid Itokawa, scientists have found that it is a loose “heap of rubble” that easily absorbs impact energy. In this state, the asteroid has been preserved for more than four billion years, which indicates the exceptional stability of such objects.
Last fall, the DART impact probe collided with the asteroid Dimorph, noticeably changing its orbit. This was the first test of the concept of protecting the Earth from a possible asteroid threat.
And it was successful, confirming that in the extreme case, the impact will allow the celestial body to be diverted from a dangerous trajectory. However, a new study of the Itokawa asteroid has shown that this approach may not always work.
The near-Earth asteroid (25143) Itokawa is an elongated celestial body about 500 meters long, which was visited in 2005 by the Japanese probe Hayabusa. He collected and delivered to Earth dust samples from the surface of an asteroid.
Fred Jourdan and his colleagues studied these materials using reflected electron diffraction (which allows you to determine the internal texture and orientation of microscopic crystals), and also determined the age by argon dating.
Such work confirmed that Itokawa belongs to a type of astronomical object sometimes referred to as a ” rubble pile”.
It is believed that over time, monolithic asteroids sooner or later collide with each other and are destroyed, and only part of their fragments are held together by their own gravity, forming loose, about half of the emptiness “heaps of rubble.”
This is how a large part of the asteroids are arranged, but how long they can last in this state is unclear.
The dating of Itokawa showed that it lasted as a “rubble heap” for a very impressive time – at least 4.2 billion years. This is orders of magnitude larger than monolithic asteroids can survive.
“This long lifespan for a ‘rubble pile’ of this size may be due to the absorbent properties of its material,” said Fred Jourdan.
“In short, we showed that Itokawa is like a huge space pillow, so it is very difficult to destroy it.”
If “heaps of rubble” are able to survive for a much longer time than monoliths, then most likely most modern asteroids belong to this type of celestial bodies.
Unlike the Dimorph encountered by DART, they can absorb impact energy and react less noticeably.
And this, according to scientists, calls into question the effectiveness of our approach to protecting the Earth from an asteroid threat.
“We can potentially take a more aggressive approach,” said co-author Professor Nick Timms.
“For example, use the shock waves from a nearby nuclear explosion to knock a “pile of rubble” out of the way or disperse it.”
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