Everybody knows that water is necessary for life, at least as we know it. Everybody knows liquid water is necessary for life, at least as we know it. A friend of mine once had a poster on his office wall that asked at the top in big letters “WHY IS THE SKY BLUE? I first saw the poster from a distance, and my initial reaction was to snicker slightly, thinking “Everybody knows why the sky is blue. The rest of the poster proved to be the perfect rejoinder, for beneath that simple question lay row upon row of complex equations, originally published by Albert Einstein in 1911, that described in mathematical terms why are enzymes necessary to all living things why the sky is blue.
When I looked beneath the surface of it, the question that opens this article elicited a similar effect: I was surprised by how much I didn’t know about why water is thought necessary for life. Once I learned the particulars, it became clear why planetary scientists on the lookout for life on Mars and elsewhere in the solar system are on the lookout for water. So why is liquid water the sine qua non of life as we know it? The biochemical reactions that sustain life need a fluid in order to operate. In a liquid, molecules can dissolve and chemical reactions occur.
And because a liquid is always in flux, it effectively conveys vital substances like metabolites and nutrients from one place to another, whether it’s around a cell, an organism, an ecosystem, or a planet. Getting molecules where they need to go is difficult within a solid and all too easy within a gas—vapor-based life would go all to pieces. And why is water the best liquid to ap biology review science practice 1 the job? For one thing, it dissolves just about anything. Water is probably the best solvent in the universe,” says Jeffrey Bada, a planetary scientist at the Scripps Institution of Oceanography in La Jolla, Calif.