Arsenic and Old Lifeforms

Interesting piece by Paul Davies in the latest Scientific American. Davies discusses the search for biota that might have arisen in separate biogenesis events here on Earth, the current searches for extremophiles one obvious example of that. However, none of the extremophiles found to date indicate a separate origin.

Some of the more interesting inquiries are looking at indicators of organisms too small to bear ribosomes:

In 1990 Robert Folk of the University of Texas at Austin drew attention to tiny spheroidal and ovoid objects in sedimentary rocks found in hot springs in Viterbo, Italy. Folk proposed that the objects were fossilized “nannobacteria” (a spelling he preferred), the calcified remains of organisms as small as 30 nanometers across. More recently, Philippa Uwins of the University of Queensland has discovered similar structures in rock samples from a deep-ocean borehole off the coast of Western Australia.

Also of great, geeky interest are hypotheses of life forming on an early Earth with arsenic standing in lieu of phosphorus. Phosphorus is central to our biology - DNA's backbone, the energy cycle, the very membranes of our cells all rely on humble P. How very alien would life be if big brother As played those roles.

via Carl Zimmer