Exobiology, or more correctly, astrobiology, is the study of life outside the boundaries of Earth.  The possibility, the evolution, the distribution, and the future of life away from Earth.  It’s concerned not just with what you might find crawling across an alien landscape, but in the landscape itself; in recognizing and exploring diverse biospheres.  It is interested in the universal evolution of life, not just the terrestrial evolution of life.

Yellow Mite (Lorryia formosa), Image: Erbe, Pooley: USDA, ARS, EMU

While still new among the empirical sciences, astrobiology (as in all the astrosciences) is multidisciplinary.  It encompasses physics, chemistry, biology (of course), paleontology, astronomy, and planetology… to name a few.  It deals mostly with proven scientific fact and less with theory and conjecture than what you might initially think.  When you get right down to it, the only thing theoretical about the subject is that life is possible in places other than Earth, and that’s barely a stretch.  Really, we have more evidence for the existence of life outside Earth’s biosphere than we do for the existence of intelligent life within it.  Seriously.  It’s hard enough to define “life” without throwing in a completely subjective, umbrella term like “intelligence” to further limit the field.

I'm not even gonna' say it.

Knowing that I’m probably causing a few bipedal, carbon-based, Earth-bound life forms to swell up and take umbrage, I still must point out that our understanding of “life” is in its infancy.  Not its “meaning”, or “purpose” (that’s philosophy); but the nature of life itself.  Astrobiology attempts to look at the possibility of life so diverse that we might not even consider it “life”.  It looks at different possible environments, then at what kinds of life may have evolved in response to the environments.  That’s the way it works, after all.  Environments don’t change to benefit the life forms within it, the life forms change in response to the environment.  That or they become extinct.

While astrobiology may be about life in places other than here, so far everything we know is based on what happens here on Earth.  That’s limiting, true; but it still gives us a rich field with which to work.  After all, we are part of the universe.  We’re not an island off by ourselves.  If we look at Earth as a jumping-off place in considering what extraterrestrial life may be like, we can come up with some very interesting theories.  We can even theorize that for almost any possible environment, some life form has evolved to take advantage of it.  Just because we wouldn’t survive in some of these environments doesn’t mean that something hasn’t evolved to survive there.  This isn’t a new idea, by the way.  Literature has been kicking the concept around for centuries.  Remember Terry Pratchett’s The Dark Side of the Sun?  Sundogs, sentient planets, and a telepathic body of water?

Bacteriophage injecting its genome, Image: Graham Colm, all rights reserved

Well, why not?