Thursday, July 19, 2012

Titan's Seasons Do The Twist

"You should see my little Sis. She really knows how to rock. She knows how to twist!" And so does a vortex which has appeared at the southern pole of Saturn's moon, Titan. It's a sign that the seasons are changing! Thanks to images taken with NASA's Cassini spacecraft, we're able to join in the dance.

“The structure inside the vortex is reminiscent of the open cellular convection that is often seen over Earth’s oceans,” said Tony Del Genio, a Cassini team member at NASA’s Goddard Institute for Space Studies, N.Y. “But unlike on Earth, where such layers are just above the surface, this one is at very high altitude, maybe a response of Titan’s stratosphere to seasonal cooling as southern winter approaches. But so soon in the game, we’re not sure.”

Cassini originally spotted a “hood” of high-altitude haze - along with a vortex - when it first arrived at Saturn in 2004. This swirling gas around the pole has been monitored by several instruments which have been keeping watch for signs of changing seasons - most notably the southern winter. The northern "hood" has remained and the upper atmosphere has been trekking from the highlighted north pole to the cooling south. Apparently this movement is causing "downwellings" over the southern pole - the reasons for the appearance of high-altitude haze and the vortex.

“We’ve been watching this vortex become more developed in the last three to four months, and now, captured in exquisite detail, we’re seeing finer scale features within the detached haze than have been seen to date,” said Jason Perry, an imaging team associate at the University of Arizona, Tucson.

Cassini’s visible light cameras was the first to pick out the beginning haze starting to well over Titan’s south pole in March, and the spacecraft’s visual and infrared mapping spectrometer (VIMS) obtained false-color images on May 22 and June 7.

“VIMS has seen a concentration of aerosols forming about 200 miles [300 kilometers] above the surface of Titan’s south pole,” said Christophe Sotin, a VIMS team member at NASA’s Jet Propulsion Laboratory, Pasadena, California. “We’ve never seen aerosols here at this level before, so we know this is something new.” What's more, on June 27 during a distant flyby, Cassini’s imaging cameras caught a great view vortex over the south pole of the south in visible light... and in unsurpassed detail.

“Future observations of this feature will provide good tests of dynamical models of the upper atmosphere,” said Bob West, deputy imaging team lead at JPL.

Thanks to Cassini’s newly inclined orbits - the next phase of Cassini Solstice Mission - the new, detailed images may soon become commonplace. Up until now, Cassini was orbiting the equatorial plane and the previous images of the polar vortex were taken from above Titan’s equator. These images revealed changes in the haze layer on the limb over the south polar region.

“I believe we are seeing some fascinating events on the way to the formation of the south polar vortex, said West. “Future observations of this feature will provide good tests of dynamical models of the Titan circulation, chemistry, cloud and aerosol processes in the upper atmosphere.”

And I believe we'll all be watching. "Come on little Sis... Do the twist!"

Submitted by Tammy Plotner. Original Story and Image Source: JPL/NASA News Release - Cassini Solstice Mission.

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