[ExI] weird life?

[Damien Broderick]

Does Earth harbour a 'shadow biosphere' of alien life?

Monday, 16 February 2009

by Holly Hight
Cosmos Online

CHICAGO: A 'shadow biosphere' of 'weird life' unrelated to life as we 
know it might exist on Earth, giving new insight into how common life 
might be elsewhere in the universe, astrobiologists say.

Finding life that doesn't fit with the types we already know would be 
a strong indication that life developed more than one time even on 
Earth, increasing the chances of finding it elsewhere, said Paul 
Davies, an astrophysicist at Arizona State University in Tempe.

But nobody has ever seriously searched for microorganisms - or any 
form of life - different from the carbon-based, DNA-centred type of 
life about which we have long known.

If we do look, Davies said, "It's entirely feasible that we'll find a 
shadow biosphere," he told reporters at the annual meeting of the 
American Association for the Advancement of Science in Chicago.

"Our search for life [has been] based on our assumptions of life as 
we know it. Weird life and normal life could be intermingled, and 
filtering out the things we understand about life as we know it from 
the things we don't understand is tricky."

The tools and experiments researchers use to look for new forms of 
life - such as those on missions to Mars - would not detect 
biochemistries different from our own, making it easy for scientists 
to miss alien life, even if was under their noses.

"When you don't know what you're looking for or what it'll look like, 
you have to come up with a whole scientific method for how to go 
about [looking for] it," added Steven Benner, a Fellow at the 
Foundation for Applied Molecular Evolution and The Westheimer 
Institute for Science and Technology in Gainesville, Florida.

Scientists are looking in places where life isn't expected - for 
example, in areas of extreme heat, cold, salt, radiation, dryness, or 
contaminated streams and rivers. Davies is particularly interested in 
places that are heavily contaminated with arsenic, which, he 
suggests, might support forms of life that use arsenic the way life 
as we know it uses phosphorus.

If we do discover exotic life unrelated to ours, it might not have 
developed here, Davies said. Instead, it might have originated 
elsewhere, then hitchhiked to Earth by piggybacking on a meteorite.

But it doesn't matter where it originated, Davies argued, because 
it's still an indication that life has cropped up from scratch in 
more than one place.

"If it's happened more than once in the Solar System, then the 
Universe will be teeming with life," said Davies.