Does Water Really Have To Mean Life?

bigweenie asks: "With the frozen mud on the Moon's pole and the springlike seepage of water out of the lowest valley walls of Valles Marinaris, everyone seems to have a heightened urgency and hope to find life on the Red Planet (past or current). My question is, what is the link between water and life? What exactly is the biochemical, environmental, evolutionary, physiological and, God forbid, logical evidence that water is suggestive of life? All the Mars 'search for life' experts have spent the last 20 years proving life can exist anywhere under almost any conditions; no oxygen, no H2O, etc. I wish to know the real hard data and analyses that defines the relationship between water and life, and how optimistic should we be about life on Mars just because it is there in abundance." Assuming that other life exists, it is possibility of extra-terrestrial life similar to earth-life that provide a good deal of momentum to our collective interest. Since water is an absolute necessity for Earth based life, it is assumed that the presence of it elsewhere may mean the presence of lifeforms closer to what we know and understand.