The blogosphere and mainstream media have been buzzing for the past day or so about a new finding that changes our view of alien life. If you were looking for Little Green Men, you’ll be disappointed; but if you like my 2008 book on Astrobiology, then you’ll realize the scientific importance of this discovery.
The new discovery is not surprising on the theoretical level. Astrobiologists are always considering alternate chemistry for potential life, so a life form that uses arsenic in place of phosphorus has always been in the realm of the theoretically possible. (Phosphorus is an important element in the “backbone” of DNA.) But the discovery of such organisms on the shores of Mono Lake in California turns hypothesis into fact.
Whenever I talk about astrobiology, one of my main themes is that life is an opportunistic phenomenon. It seems to arise in very challenging environments on Earth, so it is reasonable to assume that it arises elsewhere whenever conditions are suitable–including other worlds. This discovery broadens the kinds of life that astrobiologists can legitimately consider in observing the worlds of this and other solar systems.
In my book, I include a short section on life with other kinds of chemistry. I don’t explicitly mention arsenic replacing phosphorous, but I do follow the lead of Peter Ward’s outstanding book Life As We Do Not Know It in discussing the possibility of life on Saturn’s hydrocarbon-rich moon Titan. That life might be based on silicon and could possibly use ammonia as the liquid that carries the vital chemicals.
Though carbon-based life with phosphorus in its DNA still seems most likely for Little Green Men, this new discovery opens up a whole new set of possible chemistries for simpler life forms.
For more details on the new discovery, follow this link to the online Astrobiology Magazine.