Even a "small" asteroid of about 200 metres (660 feet) would cause "widespread damage and loss of life" if it collided with Earth, according to astronauts Stanley Love and Edward Lu.

Faced with this threat, many scientists have explored the option of docking a spacecraft to an earth-threatening asteroid in order to deflect its course.

However the US astronauts note that asteroids are "likely to be rough and unconsolidated, making stable attachment difficult" especially as "most asteroids rotate".

Their proposal has the advantage that docking is not required: the spacecraft merely "hovers nears the asteroid with its thrusters angled outwards so that the exhaust does not impinge on the surface".

"The spacecraft tows it without physical attachment by using gravity as a towline," the astronauts propose.

According to their calculations, "a 20-tonne gravitational tractor hovering for one year can deflect a typical asteroid of about 200-metre diameter given a lead time of roughly 20 years".

Scientists estimate that the meteorite which hit the Mexico area 65 million years ago, wiping out the dinosaurs, would have measured five to 15 kilometres (3.1 to 9.3 miles) in length.

NASA's asteroid monitoring programme hopes to identify 90 percent of the thousand or so potentially Earth-threatening asteroids measuring more than a kilometre wide by the end of 2008.

All rights reserved. © 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.

Related Links
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express