How to protect the Earth from a pile of stones

Scientists are thinking about how to protect our planet from “pile of rocks” asteroids. They are loose bodies held together only by gravity. The traditional method of deflecting space rocks may fail to be effective with them.

Астероїд Бенну — об'єкт типу «купа каміння»
Asteroid Bennu is a “pile of rocks” type object. Source: NASA/Goddard/University of Arizona

“A pile of rocks”

Scientists from different countries have recently published a lot of materials on what to do if our planet is threatened by a “pile of rocks” asteroid. The traditional view of the problem of space rocks is that we should use a kinetic impact to deflect them from their dangerous course.

Last year’s DART experiment was conducted, during which an impactor probe hit the asteroid Dimorphos, demonstrating the high efficiency of this method. Even a small projectile hitting close to the center of mass of a celestial body can significantly change its trajectory.

However, the same experiment showed that such a scenario can lead to the formation of a large cloud of fragments. This is especially dangerous in the case of bodies of the “pile of stones” type. They consist of a huge number of small stones that are held together solely by gravity.

The recently explored asteroids Ryugu and Bennu (the material from these bodies have been recently returned to Earth) are of this type. And we don’t yet know what is actually hidden beneath their surface, nor how many more such “piles of stones” are roaming in the vicinity of the Earth.

The problem of splitting

The Vera Rubin Observatory is expected to be put into operation in the coming years. It will allow us to track most of the dangerous asteroids close to the Earth. However, this will not solve the problem of removing “pile of rocks” from the planet.

The fact is that a kinetic impact is likely to destroy such an object. And this is only good in Hollywood movies. In reality, the trajectory of the debris would be extremely difficult to determine and they could be still large enough to cause disaster on Earth.

So scientists propose other ways to prevent a disaster. One of them is the use of an ion engine probe. The latter is capable of generating thrust for months. So, if you put the device on the surface of a “pile of stones” and give it constant acceleration, it will simply turn off the dangerous course.

Another way is to use a gravity tractor. If the asteroid is relatively small, then a massive spacecraft nearby will simply create enough gravity to deflect it away from the Earth.

Based on materials from