12 May 1998
For Want Of A Hoover
In a paper almost designed to send the makers of vacuum cleaner advertisements scampering for their drawing boards, scientists at two institutions have added spice to the ongoing dino-debate with a new theory concerning their extinction. It was, they say, nothing so apocalyptic as a comet that wiped them out. No, it was just dirty old dust.
Publishing their ideas in last week's journal Science, Stephen Kortenkamp of the Carnegie Institution's Department of Terrestrial Magnetism and Stanley Dermott, chairman of the University of Florida's astronomy department, evoke a scenario whereby a collision between "rubble pile" asteroids in the asteroid belt might have caused a massive shower of cosmic dust to cascade upon the earth over millions of years.
Such a shower, they suggest, would alter the earth's climate sufficiently to account for "gradual mass extinctions lasting on the order of a million years." Add to that the danger of asteroid fragments up to a kilometre across (also resulting from the cosmic pile-up) smashing into the planet, and you have a formula for some serious extinction.
The earth currently accumulates around 30 000 tonnes of cosmic dust each year from interplanetary space. The largest of the dust particles is said to be a mere tenth of a millimetre thick - scarcely visible to the naked eye. Nothing, then, our hoovers can't handle.