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Is there a "shadow biosphere" on Earth?

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There are a couple of bizarre mysteries on Earth that some scientists believe can only be explained by a "shadow biosphere" full of bizarre, undetectable microbes. Think of these as the "dark matter" of our planet's ecosystems. So what makes the shadow biosphere such a plausible theory?

First, there's the phenomenon known as desert varnish (see photo). It's an odd geological phenomenon, found in California and Chile deserts, where a nacreous sheen forms on top of rocks and sand. The sheen is made up of manganese, arsenic and silica, and scientists have not been able to explain why it forms. One possibility are microbes whose digestive process produces the varnish as a waste product.


According to a fascinating article by Robin McKie, featured on Raw Story:

Professor Carol Cleland, of Colorado University, has a very different suggestion. She believes desert varnish could be the manifestation of an alternative, invisible biological world. Cleland, a philosopher based at the university’s astrobiology centre, calls this ethereal dimension the shadow biosphere. “The idea is straightforward,” she says. “On Earth we may be co-inhabiting with microbial lifeforms that have a completely different biochemistry from the one shared by life as we currently know it.” . . .

The concept of a shadow biosphere was first outlined by Cleland and her Colorado colleague Shelley Copley in a paper in 2006 in the International Journal of Astrobiology, and is now supported by many other scientists, including astrobiologists Chris McKay, who is based at Nasa’s Ames Research Centre, California, and Paul Davies.

These researchers believe life may exist in more than one form on Earth: standard life – like ours – and “weird life”, as they term the conjectured inhabitants of the shadow biosphere. “All the micro-organisms we have detected on Earth to date have had a biology like our own: proteins made up of a maximum of 20 amino acids and a DNA genetic code made out of only four chemical bases: adenine, cytosine, guanine and thymine,” says Cleland. “Yet there are up to 100 amino acids in nature and at least a dozen bases. These could easily have combined in the remote past to create lifeforms with a very different biochemistry to our own. More to the point, some may still exist in corners of the planet.”


Some astrobiologists have suggested that these microbes might be metabolizing amino acids that our bodies ignore. At Harvard University, researchers with the Harvard Origins of Life Initiative have designed a series of tests to attract microbes that consume these kinds of amino acids.


Meanwhile, there is another mystery that a shadow biosphere might solve. Earth's carbon output, from all life and industry, does not actually add up to the amount of carbon in the atmosphere. We cannot account for five percent of the carbon in the atmosphere. Where is it coming from? It could be these weird microbes in the shadow biosphere. Of course, it could also simply be a miscalculation. But scientists want to investigate further before writing off such a large discrepancy as mere error.


Soon we may find that life on Earth is more alien than we thought.

Read more via Raw Story

Photo of desert varnish by Bruce Horrocks, via EPOD.