This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: If a dangerous asteroid were headed toward Earth, one defense could be a nuclear detonation to blast one side with X-rays and nudge it off course. But new simulations suggest that for a lumpy, irregular asteroid, exactly where those X-rays hit could make a huge difference.
In a study published in Icarus, researchers found that irradiating different sides of the same simulated asteroid changed how much momentum the blast imparted and how much spin it induced. In one case, the deflection velocity—the change in its linear speed after the simulated X-ray burst—was 3.9 millimeters per second from one angle, but just 0.8 millimeters per second from another: a nearly fivefold difference. "We expected aim to matter," said Nathan Moore, a physicist at Sandia National Laboratories who led the research.
"What surprised us was how much." For a different asteroid, the change in its rotational speed after deflection—how fast it spun—varied by a factor of 17. The findings underscore that in a real attempt to use a nuclear burst to deflect an asteroid, knowing the object's shape and choosing the right side to target could be critical. To get their data, Moore and his colleagues created the most accurate asteroid deflection model to date.
Most previous models simplified the extremely complicated problem by choosing between realistic asteroid shapes and high-fidelity math. Moore's team has created a model that includes both. The new simulations offer the most detailed look yet at the asteroid deflection problem.
"Our new algorithm is over 1,600 times faster, which was critical to this breakthrough," Moore said. "With the old models, computers just couldn't handle it." Moore has been studying the issue of accurate modeling since an experiment at Sandia's Z machine showed, for the first time, that X-rays could deflect a small piece of asteroid material. "I started wondering how to scale up the calculation to more accurately predict deflection of a full-scale asteroid." Most researchers modeled asteroids as spheres, he said.
But spherical asteroids do not exist. "You can make estimates that way, but asteroids come in all kinds of odd, lumpy shapes," he said. "That's when I latched onto some work one of my colleagues was doing related to outgassing of objects in space.
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