Eight-legged space survivor gives 'panspermia' theory new life

— -- The revelation last week that tiny eight-legged animals survived exposure to the harsh environment of space on an Earth-orbiting mission is further support for the idea that simple life forms could travel between planets.

This idea, called panspermia, is not new. It holds that the seeds of life are everywhere, and that microbial life on Earth could have traveled here from Mars or even from another star system, and then evolved into the plethora of species seen today. In essence, we may all be Martians.

In various forms, the panspermia concept was discussed among scientists in the 1700s, again in the 1800s, and then notably when Sir Fed Hoyle and Chandra Wickramasinghe popularized it about 30 years ago. Mainstream scientists often dismissed the hypothesis, however, even into the 1990s.

But new life has been breathed into the idea in the past decade.

One big question that dogged panspermia for decades has been settled, most scientists agree: Could life endure a trip from one world to another?

One key breakthrough was a 2000 study that concluded a rock from Mars, found on Earth, remained cool enough during its violent ejection from the red planet and its fiery trip through our atmosphere 16 million years later to sustain life — were there any aboard.

And the incredible survival tale of the tiny tardigrades, also called water bears, is a dramatic reminder that life can survive space travel. The dot-sized invertebrate creatures endured 10 days of exposure, and upon return to Earth, scientists found that even some of those exposed to solar radiation had made it through. Though it had already been shown that single-celled organisms could survive space, tardigrades are eight-legged animals on a different branch of the tree of life than microbes.

"It is an exciting result that seems to support the idea that life forms could be exchanged between planets such as Earth and Mars," said David Morrison, an astrobiologist at NASA's Ames Research Center.

"Now we know that species from three very different organism groups —bacteria, lichens and invertebrate animals— are able to survive at least short periods under space vacuum and also under some restricted conditions of solar radiation," said K. Ingemar Jonsson, who led the tardigrade study out of Kristianstad University in Sweden. "And if protected from sunlight, all these groups could probably survive for several months, perhaps years, in space."