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."

Comments

Sure...

[hipp5]

Sure, life in the universe COULD be different than our carbon-based, water-needing forms. But there are restrictions on how many detectors etc. you can package on one rover. Given that difficult decisions need to be made in regards to equipping our search for life, it makes sense to search for life in a form that we are 100% sure exists at least one place in the universe.

Re:Sure...

[Canjo]

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.

Re:If it evolves by replicating, it's life.

[Samantha Wright]

Perfect replication + deliberate error mechanisms = evolution. Evolution has a tolerance rate; too many mutations too quickly and your evolutionary magic turns into lethal dysfunction. The rate of evolution for E. coli, for example, is a few orders of magnitude smaller than 1/(the number of nucleotides), which means that most of the time the offspring are a perfect match. Relatedly, humans manifest a substantial number of new point mutations when the gametes are formed, but have a much lower rate when producing somatic cells through mitosis. It's replication with a very small p-value. The article discusses the thermodynamic inevitability of mutation, if you're genuinely interested.

Re:Excess sustained negentropy

[Maljin Jolt]

According to your definition of life, all my hard disks are alive!

What you have missed: 1. perception of proximity, sensing 2. behavioral intent

Re:Dumb article

[Maritz]

A mule strikes me as a cheap argument. They may be unable to reproduce, but their ancestors stretching back 4 billion + years were able to. By that argument you could castrate a man and say 'look, your definition of life is invalid'.