|Felisa Wolfe-Simon, credit NASA|
The NASA announcement concerns an alien form of life, but not alien life, per se. Over a two years study, a form of bacteria scraped off the bottom of Mono Lake in California was grownin a lab mixture containing arsenic. Gradually, it adapted to that mixture, exchangin atoms of phosphorus for atoms of arsenic.
The key here, is not that they found a bacterium capable of doing this. Rather, it means that there is the possibility of life on other planets that uses different components than we expect. Science fiction hasn't been blind to this possibility. Some may recall the Star Trek episode "The Devil in the Dark," proposed a form of life based on silicon, rather than carbon.
This NASA announcement is along the same lines. Dimitar Sasselov, an astronomer at the Harvard-Smithsonian Center for Astrophysics and director of an institute on the origins of life there commented, "There is basic mystery, when you look at life. Nature only uses a restrictive set of molecules and chemical reactions out of many thousands available. This is our first glimmer that maybe there are other options." Sasselov was not involved in the work.
Felisa Wolfe-Simon led the research. She is a NASA astrobiology fellow at the United States Geological Survey (USGS) in Menlo Park, California. She saidm, "This is a microbe that has solved the problem of how to live in a different way.”
The six basic building blocks for life on Earth have been known as carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Phosphorus, in fact, is part of the chemical structure of DNA and RNA, and is considered essential for all living cells. Arsenic, on the other hand, while chemically similar to phosphorus, is poisonous to most life on Earth.
The bacterium known as strain GFAJ-1 grew the best of all those harvested from Mono Lake. Despite its adaptation to arsenic, it still grew better on a phosphorus diet.
The implication of this NASA announcement are huge. It means that to this point, while not necessarily looking for the wrong conditions for life, we may have been excluding other conditions which could still support life. BEMs should beware, as NASA is looking for you.