We may be able to stop killer asteroids by putting them together

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Earth has been targeted by dangerously large asteroids in the past, and it will be again. The impact of such objects has historically led to mass extinctions, but the possibility exists that humanity may work to stop such an event. Various methods have been suggested to deflect potentially dangerous asteroids (PHAs), but an international team of researchers has a deceptively simple suggestion: tie them to another space rock.

Astronomers around the world scan the skies for colliding dangerous space rocks. Fortunately, we haven’t found any ongoing for an impact, but that could change at any time. The key to all the proposed methods of deflecting asteroids is to have enough time to implement a plan. If we find out about the threat a week in advance, the game is over no matter what we do. Even with time to prepare, many proposals carry their own risks. For example, techniques that rely on high-energy or explosive impacts to destroy or deflect the object are at risk of breaking it into parts that could hit Earth anyway.

The team behind the new study suggests simply tying a small asteroid to a larger, more dangerous one. PHA’s orbit, like all objects in space, is a function of gravity. These objects swing endlessly around the solar system, unless they are caught in the gravity of another object and go into a collision. If we know early enough that an asteroid is heading for Earth, we can use gravity to our advantage. Connecting a smaller space rock to the dangerous one with a harness would create a binary system with a different center of mass. Over time, the asteroid’s orbit would change and avoid disaster.

This is all purely theoretical, but the team produced a compelling simulation using the Bennu asteroid as an example. We know a lot about Bennu thanks to NASA’s recent OSIRIS-REx mission to collect samples from the surface. The simulation examined how Bennu would behave under various collision conditions, and then added the mass of another asteroid 1,000 to 3,000 kilometers away with masses between 1/1000 and 1 / 10,000 of the PHA.

The study claims that tying these objects together is enough to alter a PHA’s orbit and avoid collision over the years. However, we had better wait for the solar system to wait a bit longer to launch an asteroid towards us. While this approach is novel and low-risk, we don’t have the technology to capture an asteroid (even a small one). Connecting two objects with a 1,000 kilometer rope can also be a great engineering feat. For now.

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