*Deflected asteroids may keep coming back*
* 17 November 2007
* From New Scientist
What goes around comes around. Unfortunately, no such karma figures in
plans to deflect asteroids on a collision course with Earth, a hearing
of the US House Science and Technology Committee was told last week. One
big whack will deflect an asteroid temporarily, but does not guarantee
safety next time its orbit brings it close.
Asteroid researchers have long debated the merits of deflecting
asteroids with a powerful blast such as a nuclear explosion. However,
Rusty Schweickart, who heads an asteroid research group called the B612
Foundation, told the committee that the effects of powerful blasts are
hard to predict, especially if Earth's gravitational pull acts on the
object. An asteroid could pass through one of the "keyholes" that would
nudge it back onto a collision course, so once diverted it might need to
be steered past Earth to prevent this.
At the same hearing, members attacked NASA for ignoring smaller
asteroids. Two years ago, Congress asked NASA to plan a programme to
identify dangerous objects as small as 140 metres across, but the space
agency says it prefers to work from other surveys, such as the
Pan-STARRS telescope in Hawaii.
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