Atmospheric Vortex Discovered on Titan, Saturn's Earth-Like Moon

Atmospheric vortex likely means a seven-and-a-half year long winter is coming.

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Winter is coming, to Saturn's moon Titan, that is.

NASA scientists have caught video of a slow-swirling cloud-like formation high over the moon's south pole, which may signal that the southern hemisphere of the moon is about to go into a long winter cycle.

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NASA scientists have waited years for Titan's seasons to change. According to Tony Del Genio of NASA's Goddard Institute for Space Studies in New York, a season on Titan is about seven and a half earth years long. NASA's Cassini spacecraft, which captured the 470 mile-wide cloud formation on video, has been orbiting Saturn since 2004.

"For the first time since the mission began, we're beginning to see the southern hemisphere move towards the winter season … that was one of the goals of the Cassini mission, to watch Titan as its seasons change," he says. "We're not sure what this will tell us because we just observed [the vortex] last week."

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Titan has long intrigued astronomers because it's the only moon in the solar system to have an atmosphere, its surface is made up of ice and rock, and has other earth-like properties, according to Del Genio.

Titan's atmosphere is about 50 percent thicker than Earth and is made up of many organic chemicals found on Earth, which is of interest to chemists, he says. Titan's weather patterns are also interesting for meteorologists like Del Genio.

"It has a hydrologic cycle analogous to one on earth, and they have storms—but instead of water storms, they're made of liquid methane," he says. "And unlike Earth, which is 70 percent covered by oceans, just a small percentage of Titan is covered by methane lakes."

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That there's a vortex forming above the south pole isn't entirely shocking—scientists know that vortices happen on Saturn, Jupiter, Earth, Neptune, and Venus, but Del Genio says that studying Titan can help researchers shore up physics theories they've developed by observing earth.

"We can take our understanding of the Earth and see if we can anticipate the types of things we've seen on Titan," he says. "That's the challenge and excitement—observing Titan just gives us another piece of the puzzle."

Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at jkoebler@usnews.com