Space and Earth Sciences News

Greenbelt MD (SPX) May 27, 2009 - NASA-sponsored scientists looking back at Earth with the Deep Impact/EPOXI mission have developed a method to indicate whether Earth-like alien (extrasolar) worlds have oceans. "A 'pale blue dot' is the best picture we will get of an Earth-like extrasolar world using even the most advanced telescopes planned for the next couple decades," said Nicolas B. Cowan, of the University of Washington.

"A 'pale blue dot' is the best picture we will get of an Earth-like extrasolar world using even the most advanced telescopes planned for the next couple decades," said Nicolas B. Cowan, of the University of Washington.
"What we studied in this paper was how that blue color changes in time: oceans are bluer than continents, which appear red or orange because land is most reflective at red and near-infrared wavelengths of light. Oceans only reflect much at blue (short) wavelengths," said Cowan.
"We could erroneously see the planet as a desert world if it had a nearly solid band of continents around its equator and oceans at its poles," said Cowan.
"However, a Neptune-like world would appear as an unchanging blue using this technique, and again it's the changes in the blue color that reveal oceans to us," said Cowan. "There are some weird scenarios you can dream up that don't involve oceans but would lead to varying patches of blue on a planet, but these are not very plausible."
"A spectrum of the planet's light that reveals the presence of water is necessary to confirm the existence of oceans," said Drake Deming, a co-author of the paper at NASA's Goddard Space Flight Center in Greenbelt, Md. Instruments that produce a spectrum are attached to telescopes and spread out light into its component colors, like a prism separates white light into a rainbow.