[troutman]

http://www.planetary.org/about/press...eep_Space.html

NASA's announcement today of the discovery of bacteria from Mono Lake, California, that can use arsenic in its body instead of being poisoned by it, is significant to the search for life on other worlds. Not only do these organisms live in an extreme environment -- but they are also an extreme life form.

If we can find such an extreme combination on Earth, what may have evolved in alien environments elsewhere?
Bill Nye, the Planetary Society's Executive Director, said:

"If you or I ingest arsenic, well... it doesn't go so well. So, if we can discover arsenic-loving bacteria right under our noses in such a well-researched place as Mono Lake, who knows what else is out there, on our world or somewhere far, far away?"

Note that arsenic is immediately below phosphorus on the Periodic Table of the Elements. Perhaps you remember the silicon-based creature called horta in the original Star Trek series. The idea was that silicon is right below carbon in the periodic table; they are in the same chemical period. While swapping silicon for carbon is probably not a possibility, this is the same concept -- except that it's science, not science fiction. Arsenic is highly toxic to living things like us, but, chemically, it behaves in a similar way to phosphate

Reader Comment:

On the NASA web-tv Wolfe-Simon seems very thorough with claiming that she don't know if it is _complete_ substitution, if I understood correctly.