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The design was thought up by two NASA astronauts, Edward Lu and Stanley Love. It would require hovering a spacecraft above the asteroid's surface, allowing the spacecraft's mass to draw the asteroid towards it. The spacecraft would use thrusters to maintain a certain distance from the asteroid, and to gently move it in a different direction. These thrusters could be positioned so their exhaust passes above or below the rock, to prevent pushing against the asteroid, or stirring-up dust and ions from the surface.
Lu and Love believe their design is more feasible than other methods that require docking a spacecraft to an asteroid's surface. Very little is known about the surface of asteroids, but they are expected to consist of rough, loose material. This would make any kind of attachment to the asteroid extremely difficult. Another problem with anchoring a device on an asteroid's surface is the fact most asteroids rotate, meaning any onboard thrusters would point in a constantly changing direction.
"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,� Stanley 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.�
Their paper, published in the latest edition of Nature, suggests this method could be used on the asteroid Apophis, formally known as 2004 MN4. At the end of last year, scientists gave Apophis a one in 37 probability of striking the Earth in 2029. Astronomers have since ruled out a collision in 2029, but now believe this close shave might force Apophis to swing around and strike the Earth in 2036. The probability of a collision in 2036 is also likely to drop, but NASA are looking into various ways to deflect the object, should the need arise.
More info: Nature;Near Earth Object Information Centre;NASA
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