Scientists have used advanced computer simulations to examine whether a nuclear explosion could help protect Earth from a large asteroid on a collision course with the planet. The study, led by astrophysicist Isaiah Santistevan of Lawrence Livermore National Laboratory, examined the effects of a 1-megaton nuclear explosion on a simulated asteroid about 160 metres wide. Such an asteroid could cause catastrophic damage if it struck a populated area, while some dark asteroids can be difficult to detect early enough for conventional planetary-defence methods.
The simulations showed that a nuclear device would not necessarily have to strike the asteroid directly. Instead, an explosion several metres above its surface could release intense X-ray energy, heating and vaporising material on the asteroid's exterior. The rapidly escaping material could alter the asteroid's movement while also generating shock waves capable of cracking and disrupting its interior. Researchers used three-dimensional models based partly on the shape and porous structure of Bennu, along with information from meteorites linked to the Chelyabinsk and Aba Panu events.
In one simulation, an explosion 10 metres above the asteroid caused extensive damage, with about 98.2 per cent of the material becoming severely damaged and roughly 97 per cent moving faster than the asteroid's escape velocity. This suggested that large portions could separate and move away from one another rather than remaining together. The researchers also tested a detonation 25 metres away and found that, at one stage, it produced more widespread damage because the X-rays reached a larger portion of the asteroid's surface despite the greater distance.
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The simulations also highlighted how complex asteroid disruption can be. After 68 milliseconds, about 92.6 per cent of the asteroid was fully damaged in the 25-metre scenario, compared with 78.1 per cent in the 10-metre simulation at the same point. However, the researchers could not determine whether the resulting fragments would remain safely dispersed. Some pieces could potentially stay large enough to threaten Earth, while gravitational forces might also cause fragments to come back together over time.
Another major limitation was the enormous computing power required for the experiments. The longest simulation covered only 145 milliseconds of activity but reportedly took 59 days to complete using 1,680 computer processors. Because the researchers could not model the aftermath over much longer periods, the simulations do not establish that a nuclear explosion would reliably eliminate an asteroid threat. Instead, they provide additional information about how nuclear disruption might work if an asteroid were detected too late for other defence strategies.
The researchers concluded that asteroid disruption appeared highly likely in two of the three scenarios examined, based on the extent of damage, movement of material and changes in velocity. The findings are intended to improve understanding of nuclear mitigation as a potential last-resort planetary-defence option rather than suggest that such a response would always succeed. Further research and longer-duration simulations will be needed to determine how asteroid fragments behave after an explosion and whether they could ultimately pose a continued danger to Earth.
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