Earth has been in the crosshairs of dangerously large asteroids in the past, and it will be again. The impact of such objects has historically led to mass extinctions, but there’s a chance humanity could work to stop such an event. Various methods of deflecting Potentially Hazardous Asteroids (PHAs) have been suggested, but an international team of researchers has a deceptively simple suggestion: Tie them to another space rock.
Astronomers around the world scan the skies in search of dangerous space rocks on a collision course. Luckily, we haven’t found any on course for an impact, but that could change at any time. The key to all the proposed methods of deflecting asteroids is having enough time to implement a plan. If we learn about the threat a week in advance, it’s game over no matter what we do. Even with time to prepare, many proposals come with their own risks. For example, techniques that rely on high-energy impacts or explosives to destroy or deflect the object risk breaking it into parts that could hit Earth anyway.
The team behind the new study suggests simply tethering a small asteroid to a larger, more dangerous one. The orbit of PHAs, like all objects in space, is a function of gravity. These objects swing around the solar system endlessly, unless they get caught in another object’s gravity and spiral into a collision. If we know far enough in advance an asteroid is headed 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 avert disaster.
This is all purely theoretical, but the team did produce a compelling simulation using the asteroid Bennu as an example. We know a great deal about Bennu thanks to the recent NASA OSIRIS-REx mission to collect samples from the surface. The simulation examined how Bennu would behave under several collision conditions, and then added the mass of another asteroid between 1,000 and 3,000 kilometers away with masses between 1/1000 and 1/10,000 of the PHA.
The study claims that tethering these objects together is sufficient to alter the orbit of a PHA and avoid collision over the course of years. However, we’d better hope the solar system waits a bit longer to throw an asteroid our way. 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 tether may also be too great of an engineering feat. At least for now.
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