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Signatures of a Shadow Biosphere
Astrobiologists are aware that extraterrestrial life might differ from known life, and considerable thought has been given to possible signatures associated with weird forms of life on other planets. So far, however, very little attention has been paid to the possibility that our own planet might also host communities of weird life. If life arises readily in Earth-like conditions, as many astrobiologists contend, then it may well have formed many times on Earth itself, which raises the question whether one or more shadow biospheres have existed in the past or still exist today. In this paper, we discuss possible signatures of weird life and outline some simple strategies for seeking evidence of a shadow biosphere.

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Never mind Mars, alien life may be thriving right here on Earth, a major science conference has heard.
Our planet may harbour forms of "weird life" unrelated to life as we know it, according to Professor Paul Davies, a physicist at Arizona State University.
This "shadow life" may be hidden in toxic arsenic lakes or in boiling deep sea hydrothermal vents, he says.


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A 'shadow biosphere' of 'weird life' - unrelated to life as we know it - might exist on Earth, giving new insight into how common life is 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 here 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.

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Astrobiologists have often pondered "life as we do not know it" in the context of extraterrestrial life, says Paul Davies, an internationally acclaimed theoretical physicist and cosmologist at Arizona State University. "But," he asks, "has there been a blind spot to the possibility of 'alien' life on Earth?"
Davies will challenge the orthodox view that there is only one form of life in a lecture titled "Shadow Life: Life As We Don't Yet Know It" on Feb. 15 at the annual meeting of the American Association for the Advancement of Science. His presentation is part of the symposium "Weird Life."

"Life as we know it appears to have had a single common ancestor, yet, could life on Earth have started many times? Might it exist on Earth today in extreme environments and remain undetected because our techniques are customised to the biochemistry of known life?" - Paul Davies, who also is the director of the BEYOND Centre for Fundamental Concepts in Science at Arizona State University in the College of Liberal Arts and Sciences.

In the lecture, Davies will present, challenge and extend some of the conclusions from a July 2007 report by the National Research Council. That report looked at whether the search for life should include "weird life" - described by the Council as "life with an alternative biochemistry to that of life on Earth."

"If a biochemically weird microorganism should be discovered, its status as evidence for a second genesis, as opposed to a new branch on our own tree of life, will depend on how fundamentally it differs from known life," wrote Davies in the Nov. 19, 2007, issue of Scientific American.

Davies and other pioneers who speculate that life on Earth may have started many times are wondering "why we have overlooked this idea for so long?"

"[The concept of a shadow biosphere] is still just a theory. If someone discovers shadow life or weird life it will be the biggest sensation in biology since Darwin. We are simply saying, 'Why not let's take a look for it?' It doesn't cost much (compared to looking for weird life on Mars, say), and, it might be right under our noses" - Paul Davies.

Davies, whose research is steeped in the branches of physics that deal with quantum gravity - an attempt to reconcile theories of the very large and the very small - is a prolific author (27 books, both popular and specialty works) and is a provocative speaker (he delivered the 1995 Templeton Prize address after receiving the prestigious award for initiating "a new dialogue between science and religion that is having worldwide repercussions").

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-- Edited by Blobrana at 23:20, 2009-02-15

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