| What is Life ? |
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Obviously the first question that must be addressed before attempting to understand the origins of life on our own planet and searching for it on other worlds, is in defining what ‘life’ actually is in the first place.
Although it may be relatively easy to point to things in the world today and classify them as living or dead, a precise, unambiguous definition that will work even for lifeforms we’ve never encountered before is a little more tricky. All life on Earth is built from long chains of carbon atoms and needs liquid water, with cells using DNA to store their operating instructions and proteins to carry out most of the crucial biochemical processes. But what makes astrobiologist think that life elsewhere would necessarily be carbon-based and needing liquid water? Could life be silicon-based or depend on solvents other than water? The simple answer is that we don’t know, although we do know it’s definitely possible with carbon and water so looking for this kind of biochemistry seems to be the best bet for now. A more conceptual definition of life is that it is a self-replicating system containing a coded description of itself, able to extract energy from the environment to maintain its own complexity and reproduce – this defines life by what it does, not by what it’s made of.
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| Last Updated on Thursday, 10 May 2007 14:10 |