Nestled safely inside the belly of a comet orbiting some unknown
star, a microscopic alien sits dormant. Somewhere in this vast
universe -- perhaps a place like Earth -- a greater destiny awaits
the microbe. A place to flourish, become a nematode or a rose or a
Life, after all, is tenacious and thrives on change.
Over time, gravity performs a few plausible, but not routine
tricks, and the comet is ejected from its stellar orbit like a rock
from a slingshot. For more than a 100 million years it slips
silently across the inky vastness of interstellar space.
Then gravity goes to work again. Another star tugs at the comet,
pulls it in.
A few giant gaseous planets whiz by, their bulks tugging at the
comet, altering its course slightly. Ahead now, growing larger,
looms a gorgeous blue and brown marble. Water and land. Maybe some
Then with the force only the cosmos can summon, the comet slams
into the third rock from a mid-sized, moderately powerful star. The
alien microbe survives, emerges from its protective shell and
spreads like the dickens.
Thus began life on Earth, 3.8 billion years ago.
Or so goes one aspect of a theory called panspermia, which holds
that the stuff of life is everywhere and that we humans owe our
genesis and evolution to a continual rain of foreign
microbes. It means, simply, that we might all be aliens.
It's an idea that has been around longer than Christianity, but
which still struggles to gain strong support among most
But two recent discoveries are breathing new life into the
One study, reported in the October 27 issue of the journal
Another group of researchers, reporting in the October 19 issue
of Nature, claims to have found and revived bacteria on Earth
that were dormant, in the form of spores, hiding in New Mexican salt
crystals for 250 million years. Scientists called the implications
of this second discovery profound, suggesting that if further study
bears out the findings, it could mean bacterial spores are nearly
And if you are immortal, then what are a few billion years of
"Until recently, panspermia was not even regarded as a scientific
hypothesis," says Chandra Wickramasinghe, the concept's leading
proponent. "Now that has changed."
Agreement, but still caution
In interviews with more than a half dozen respected scientists in
diverse fields, it's clear that panspermia, or at least some aspects
of the theory, is poised to jump to the forefront of study among
scientists who seek to understand where and how life began. While
the prevailing theory holds that life arose spontaneously out of a
terrestrial, chemical soup, panspermia's defenders argue that such a
miracle could happen almost anywhere.
This means we could have microbial ancestors, or even more
evolved cousins, in unexplored corners of the cosmos.
"Both (new) studies lend a healthy boost to the plausibility of
panspermia," says Jay Melosh, a geophysicist at the University of
Arizona's Lunar and Planetary Laboratory. "I just submitted a paper
to (the journal) Icarus that says that an interstellar
journey is overwhelmingly improbable. However, a number of
factors -- including the recent Nature article -- are making
me rethink this."
Like other scientists, Melosh still calls the interstellar
transfer of life improbable, but expects research into the idea to
Panspermia: Its own origins and evolution
The idea that the seeds of life are ubiquitous throughout the
cosmos goes back to Anaxagoras, a Greek philosopher. In the 1800s,
French chemist Louis Pasteur proposed that spontaneous generation of
life could not have occurred on Earth. British physicist Lord Kelvin
and others jumped on Pasteur's bandwagon and suggested that life
might have come from space.
But modern-day panspermia advocates have been the Rodney
Dangerfields of science.
In fact, just two leading researchers carry the bulk of the
panspermia torch. The renowned Sir Fred Hoyle, known for his studies
of star structure and the origin of the chemical elements in stars,
has worked with Chandra Wickramasinghe over the past three decades
to pioneer the modern theory of panspermia.
In the 1970s, Wickramasinghe and Hoyle found what they say are
traces of life in the dust around distant stars. The duo then
broadened the panspermia theory, arguing that a continual rain of
life-altering stuff from space -- including