Saturday, July 16, 2005

the meaning of "life"

Recently while perusing some bioinformatics literature I ran across a reference to NASA's definition of "life." This comes from their Astrobiology Institute where they are interested in detecting evidence of extraterrestrial life. I guess if you are looking for "biosignatures" it helps if you know what the signature is a signature of.

This is what I found in their Ask the Astrobiologist section:
While there are many contending definitions, one that is generally accepted comes from Bruce Jakosky's book, "The Search for Life on Other Planets." NASA scientist Jakosky defines being "alive" in general terms if the object 1) utilizes energy from some source to drive chemical reactions, 2) is capable of reproduction, and 3) can undergo evolution. Of course, this definition is subject to several complications. For example, fire can reproduce itself, contains heat energy, and uses biogenic elements (carbon, hydrogen, oxygen, nitrogen, phosphorous, and sulfur). And yet, fire is classified as a byproduct of non-biological chemical reactions in part because it cannot evolve. In fact, another definition of life by geologist Joseph Kirchvink emphasizes evolution as the only defining characteristic of living objects versus non-living ones.
I wonder if this means that if you reside in Kansas you aren't alive because you haven't evolved?

Advice to Kansas: Get a Life.