Hot topic in movies - when to the planetan asteroid is approaching, threatening to destroy all life, and a team of superheroes is sent into space to blow it up. But approaching asteroids may be more difficult to break than previously thought, a study from Johns Hopkins University shows. Scientists made a simulation of an asteroid collision and gained a new understanding of rock destruction. March 15 work will be published in the journal Icarus.
Its results can help create strategies for countering and rejecting asteroids, improve understanding of the formation of the solar system, and help develop useful resources on asteroids.
How to destroy an asteroid?
“We used to believe that the larger the object, theit is easier to break because larger objects are more likely to have weak spots. However, our results show that asteroids are stronger than we thought, and more energy is required for total destruction, ”says Charles El Mir, the first author of the work.
Scientists understand the physics of materials - like rocks -on a laboratory scale (by studying them on fist-sized samples), but it is difficult to transfer this understanding to objects the size of a city, like asteroids. In the early 2000s, other scientists created a computer model into which various factors could be introduced, such as mass, temperature and material fragility, and simulate an asteroid about a kilometer in diameter that falls into a target asteroid 25 kilometers in diameter at a speed of 5 km / s. Their results showed that the target asteroid would be completely destroyed as a result of the impact.
In a new study, El Mir and his colleagues introducedthe same scenario in the new computer model of Tonga-Ramesh, which takes into account the small-scale processes occurring during the collision, in more detail. Previous models did not take into account the limited rate of propagation of cracks in asteroids should be.
“We wondered: how much energy is needed to actually destroy an asteroid and break it into pieces,” says El Mir.
The simulation was divided into two phases: short-term phase of fragmentation and long-term phase of gravitational re-accumulation. In the first phase, the processes that begin immediately after the asteroid hit the target, the processes of a fraction of a second in length were considered. The second phase, longer, implies the effect of gravity on the parts that fly from the surface of the asteroid after impact; many hours after the collision, gravitational re-accumulation also occurs, the asteroid is rebuilt under the action of its own attraction.
In the first phase after the defeat of the asteroid on itmillions of cracks formed, part of the asteroid melted, a crater appeared at the site of impact. At this stage, individual cracks were studied and the general patterns of propagation of these cracks were predicted. The new model showed that the asteroid will not fall apart from the impact, as previously thought. Moreover, since the asteroid did not collapse in the first phase of the collision, in the second phase it even became stronger: the damaged fragments were redistributed around a larger, new nucleus. According to the results of the study, it was necessary to revise both the energy required for the destruction of the asteroid and possible loopholes for the asteroid's subsurface for those who would like to develop it.
"Small asteroids quite often come to us -Like events in Chelyabinsk a few years ago. It remains only a matter of time when these questions will move from academic to defining our response to a serious threat. We must have a clear idea of what to do when the time comes - and scientific efforts like these are crucial for making decisions. ”
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