Asteroids consisting of comparatively loose accumulations of debris are apparently a much greater threat to Earth than previously assumed. This was the result of analyzes carried out at Australia’s Curtin University on rock samples from the Japanese space probe Hayabusa 1. They come from the asteroid Itokawa and have therefore shown that it is orders of magnitude older than previously suspected. The celestial body is the result of a collision 4.2 billion years ago. This “surprisingly long survival time” made it clear how difficult it is to destroy asteroids that only consist of rubble. This has consequences for possible measures, should such an object crash into the earth.
Orders of magnitude older than expected
Until now, it was not known how old such asteroids can get, but this has consequences for estimates of their distribution in the solar system, the team explains. In the case of monolithic asteroids, i.e. massive chunks of rock, it is assumed that they can only be a few hundred million years old in the asteroid belt. Given the age of the Earth and the solar system, that’s not very much. The fact that the rubble asteroid Itokawa is almost as old as the solar system and therefore older than the monolithic asteroids by orders of magnitude came as a complete surprise. The research was published in the Proceedings of the National Academy of Sciences.
“In short, we found that Itokawa resembles a giant space cushion that is very difficult to destroy,” research leader Fred Jourdan summarizes the findings. Unlike a massive chunk of rock – which is what asteroids are commonly thought of as – such a “debris pile asteroid” can literally absorb impacting objects. About half of the asteroid is made up of voids, the team explains. But if small objects such as other asteroids cannot destroy these huge accumulations of debris, then the concepts for asteroid defense that have been discussed so far would also have less of a chance of success, the team explains the significance of the find.
If an asteroid were to be discovered in the future that posed a threat to Earth, it was previously believed that an impacting probe could deflect it so far that it missed Earth. A successful test of this concept took place just a few months ago with NASA’s Dart probe. In the case of porous asteroids like Itokawa, however, this could fail because comparatively little kinetic energy is transferred, the research team explains. At the same time, we now know that these asteroids are likely to be significantly more numerous than expected. That’s why you have to think about how to ward them off. The detonation of an atomic bomb in their vicinity would therefore be conceivable. This could transfer more kinetic energy.
(my)
