Sept. 21, 2007 — Though it receives only a tiny fraction of sunlight, the planet Neptune puts what it gets to good use, creating a seasonal hot spot at its polar region that is venting methane gas into space.
The observations, reported in this week's issue of Astronomy and Astrophysics, may explain why Neptune — 30 times further from the sun than Earth — has the most wicked winds in the solar system. At that distance, the planet receives about one-thousandth the amount of sunlight as Earth.
"The wind blows there at more than 2,000 kilometers per hour (240 mph)" said lead author Glenn Orton, with NASA's Jet Propulsion Laboratory in Pasadena, Calif.
The stiff winds are caused by a seemingly slight temperature variation between Neptune's south pole, which is tilted slightly toward the sun in summer, and the rest of the planet. Orton and his colleagues determined the south pole is 10 degrees Celsius (18 degrees Fahrenheit) warmer than the planet's average temperature of minus 200 degrees C (minus 392 degrees F).
That's enough to turn frozen methane in Neptune's atmosphere into a gas, which is leaking into space, the researchers said.
What can we learn about Earth's climate from other planets? A lot.
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The temperature difference builds up over the planet's prolonged seasons. It takes Neptune 165 Earth-years to orbit the sun, so it has been summertime on Neptune's southern hemisphere for about 40 years now.
"A lot of solar energy input during that time can make big temperature differences between the regions in continual sunlight and those with day-night variations," Orton said. "This is a likely factor in Neptune having the strongest winds of any planet in the solar system."
