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Water, Water (Everywhere?)

If you want to find planets that find harbor intelligent life, you need to do what the early explorers did right here on earth: look for water.

Since the early 1990s astronomers have discovered more than 300 planets orbiting stars other than our sun, nearly all of them gas giants like Jupiter. The new generation of powerful NASA space telescopes will make it easier to spot much smaller planets that are more similar to earth.

But seen from dozens of light years away, an earth-like exoplanet will appear in telescopes as little more than a "pale blue dot." Using instruments aboard the Deep Impact spacecraft, a team of astronomers and astrobiologists has devised a technique to tell whether such a planet harbors liquid water, which in turn could tell whether it might be able to support life. Astronomer Nicolas Cowan says, "Liquid water on the surface of a planet is the gold standard that people are looking for."

When NASA scientists viewed these planets, they found two dominant colors, one reflective at long, or red, wavelengths and the other at short, or blue, wavelengths. They interpreted the red as land masses and the blue as oceans. They made maps of the planets in the dominant red and blue colors and then compared their interpretations with the actual location of the planet's continents and oceans.

Cowan says, "You could tell that there were liquid oceans on the planet. The idea is that to have liquid water the planet would have to be in its system's habitable zone, but being in the habitable zone doesn't guarantee having liquid water."

But some non-habitable planets, such as Neptune, also can appear to be blue, but the color is constant and, in the case of Neptune, likely caused by methane in the atmosphere.Cowan says, "It looks blue from every angle, the same blue all the way around. If you had an ocean planet it might look like that, but you can do other tests to determine that. For earth, the blue varies from one place to another, which indicates that it's not something in the atmosphere."

It's only a matter of time before we discover intelligent life in other parts of the universe. Some people would say they're already here! If that's what you think (or have experienced) come to our Dreamland Festival, where you can meet like-minded people (and wear the right shirt!)

Art credit: Dreamstime.com

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