NASA/University Team Develops New Method to Find Alien 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
Cowan is lead author of a paper on this research appearing in the
The maps that the team created are only sensitive to the longitudinal (East – West) positions of oceans and continents. Furthermore, the observations only pick out what is going on near the equator of Earth: the equator gets more sunlight than higher latitudes, and the EPOXI spacecraft was above the equator when the observations were taken. These limitations of viewing geometry could plague observations of extrasolar planets as well: “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.
Other things besides water can make a planet appear blue; for example, in our solar system the planet Neptune is blue due in part to the presence of methane in its upper atmosphere. “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
NASA’s Deep Impact made history when the mission team directed an impactor from the spacecraft into comet Tempel 1 on
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