Water and Life, Redux

The ink was hardly dry on last week’s report taking NASA to task for being so narrow-minded about what form alien life might take and what conditions it could live in when researchers showed that old-think has some life in it yet, no pun intended. Writing in today's issue of the journal Nature, an international team analyzing data from NASA’s Spitzer telescope, which orbits Earth, announced the first-ever discovery of water on a planet beyond the Sun--and got all excited about how important this is for the question of life beyond Earth.

More than 200 such “extra-solar” planets have been discovered, orbiting other stars. The water is actually in the planet’s atmosphere rather than sloshing around on its surface (the astronomers deduced this from how the planet absorbs starlight when it passes in front of its star, in the constellation Vulpecula—“the Fox”—64 light years away; only water vapor would produce the spectrum the Spitzer telescope captured).

The planet has the less-than-inspiring name HD 189733b, and although it is far from habitable (it is a giant gas bag, like Saturn, and 30 times closer to its star than Earth is to the sun, which makes it broiling hot: 1,340 degrees F.) the fact that it contains water suggests that the stuff might not all that rare in the galaxy.

“Our discovery shows that water might be more common out there than previously thought, and our method can be used in the future to study more ‘life-friendly’ environments,” said astronomer Giovanna Tinetti of the European Space Agency. “The holy grail for today’s planet hunters is to find an Earth-like planet that also has water in its atmosphere. When it happens, that discovery will provide real evidence that planets outside our Solar System might harbor life.”

Fair enough, and not to deny the necessity of water for life as we know it, but the crucial phrase there is “as we know it.” Astronomer Yuk Yung of the California Institute of Technology calls water “the quintessence of life as we know it.” Old paradigms die hard, and most of the ET- and planet-hunting technology currently deployed is focused on water—which, as the National Academy of Sciences reported last week, means we might be passing by quite viable planets.

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