NO NEED to despatch Bruce Willis into space with a nuclear bomb and a drill: the best way to deal with an asteroid hurtling towards Earth is gently.

Two Nasa astronauts, obviously unimpressed with the plot of the 1998 film Armageddon, say that a better solution would be to tow the asteroid out of the way using nature’s weakest force, gravity. Edward Lu, who studied applied physics at Stanford University, and Stanley Love, an expert on the collisional evolution of asteroids, propose in Nature that a 20-tonne unmanned satellite be launched if an Earth-crossing asteroid were detected. Such asteroids have the capacity to plunge the Earth into a long, dark winter.

The impact can often be predicted years or even decades in advance, from a precise knowledge of the asteroid’s orbit. So there is time to act; the discussion is about what best to do.

Asteroids are rough lumps of rubble loosely held together, the two astronauts write. That makes landing on them or tethering anything to them very tricky. Simply pushing them out of their orbit is difficult because they are in constant rotation. That means the spin would have to be arrested, or force exerted only at certain moments during the rotation, to achieve the desired effect.

Simply blowing them to bits might work but it would be difficult to predict exactly what would happen to the bits. Some might continue on an Earthwards trajectory.

So Dr Lu and Dr Love suggest an alternative. A large spacecraft hovering in space above the surface of the asteroid would exert on it a tiny force, because of gravity.

All bodies attract one another, but it is an effect usually only significiant with bodies of planetary dimensions. In this case, all that is needed is to achieve a tiny deviation of the asteroid’s path to make sure that it misses Earth. So, even the puny gravitational pull of a spacecraft would do the trick, if maintained for long enough. “This saves you from having to land on the asteroid and then trying to stabilise yourself on a flying pile of rock and debris that is spinning all the time,” Dr Love said. “By using gravity as your tow line, you can sidle up to an asteroid. Maintain it for a year and that should give it enough nudge to miss the Earth 20 years later.”

They may yet get a chance to put their plan into action. An asteroid is due to pass close to Earth on Friday, April 13, 2029.

But the chances of impact are put at comfortingly long odds of 5,560-1.

• The Science Museum in London opens a new exhibit today based on Dr Lu and Dr Love’s idea, and the asteroid due to pass close to the Earth in 2029. It is to be found in Antenna, the museum’s gallery for breaking news stories.

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