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Should Science Rethink the Definition of "Life"?
ambermichelle pointed out a story about the search for life on other planets, and the likelihood that it would be much different than what we find on Earth. With the increase of extremophile discovery in recent years perhaps it's time to reassess what the definition of "life" should be. "In November 2011, NASA launched its biggest, most ambitious mission to Mars. The $2.5 billion Mars Science Lab spacecraft will arrive in orbit around the Red Planet this August, releasing a lander that will use rockets to control a slow descent into the atmosphere. Equipped with a 'sky crane,' the lander will gently lower the one-ton Curiosity rover on the surface of Mars. Curiosity, which weighs five times more than any previous Martian rover, will perform an unprecedented battery of tests for three months as it scoops up soil from the floor of the 96-mile-wide Gale Crater. Its mission, NASA says, will be to 'assess whether Mars ever was, or is still today, an environment able to support microbial life.' For all the spectacular engineering that's gone into Curiosity, however, its goal is actually quite modest. When NASA says it wants to find out if Mars was ever suitable for life, they use a very circumscribed version of the word. They are looking for signs of liquid water, which all living things on Earth need. They are looking for organic carbon, which life on Earth produces and, in some cases, can feed on to survive. In other words, they're looking on Mars for the sorts of conditions that support life on Earth. But there's no good reason to assume that all life has to be like the life we're familiar with. In 2007, a board of scientists appointed by the National Academies of Science decided they couldn't rule out the possibility that life might be able to exist without water or carbon. If such weird life on Mars exists, Curiosity will probably miss it."
Exactly this--there might well be other forms of life, but we only really know how to look for life like our own. You may say that it's dumb for NASA to look for carbon-based life, or for SETI to look for life that uses radio wavelengths like us, but if you do so you're misunderstanding their logic. If there is enough life out there, some subset of it will be carbon based, some subset will use radio communication, and some subset will be interested in communication. That subset is the ONLY subset that we have the tools to look for. There may be non-carbon-based life, sure, but since we've never seen it we don't know exactly what its properties are or how to detect it. We may be able to theorize, but those are only theories; whereas we KNOW how life works here. It's not that researchers have a narrow definition of life, it's that we have limited resources and can only hope to detect the subset of life that is like life here on Earth.