So far, astronomers searching the universe for planets outside of our solar system have mostly discovered gas giants, like Jupiter. If you want a planet that can support life, something a bit smaller and wetter is in order. Now scientists believe they have found such a planet. It’s called Earth.
Well, obviously they haven’t only just comes across it. Using Deep Impact, a probe launched by NASA in 2005 to study a comet by smashing in to it, researchers devised a new planet-hunting method by re-discovering Earth. By imagining themselves as aliens hunting for planets like our own, they were able to ‘discover’ that Earth does indeed have liquid surface water.
By making two separate 24-hour observations of Earth’s light intensity, in wavelengths from near ultraviolet to near infrared, the researchers were able to monitor the changes in brightness as the Earth rotates and cloud-cover shifts. These changes show up as deviations from an average colour. Two wavelengths were dominant: red for long wavelengths and blue for short.
Interpreting red as land masses and blue as ocean water, the team were able to make colour maps of the planet as it rotated. Comparing this to the real Earth, the oceans became crystal clear. Nicolas Cowan, a University of Washington doctoral student, explains:
“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.”
Cowan, who is lead author of a paper explaining the research and due to be published in Astrophysical Journal, hopes that their new technique will guide the construction of future Earth-hunter telescopes. Just don’t expect to be going for an extrasolar dip any time soon.