February 24, 2004

» Panspermia revisited: is the solar system surrounded by a vast disk of frozen microbes?

But microbes might survive if they can escape the Sun's gravity more quickly. And that might happen, says Napier, if the rocks they sit on are first ground to dust1.

The Earth and her sister planets travel through a cloud of grains called zodiacal dust. This is the debris from collisions in the asteroid belt and from the passage of comets.

This dust should sand-blast anything passing through it, says Napier. This process could grind a one-metre boulder down in 20,000-200,000 years, he estimates. If a comet breaks up, thickening the dust, as happens several times each million years, the process could take as little as five centuries.

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Such a grain could travel about six light years from Earth in 70,000 years - far enough to reach other stars. We could be surrounded by a huge 'biodisk' of frozen organisms floating on grains of rock, says Napier, all of which can wander in and out of our solar system quite easily. "The solar system is as leaky as a sieve," he says.