The Cassini imaging team released today a near-true-color image and a movie taken during a flyby of Saturn's moon Titan on June 27, 2012 by the Cassini spacecraft. The image reveals a swirling, whirling vortex forming high in the atmosphere overlying the south pole of Titan, Saturn's largest moon, as the moon's southern hemisphere slowly becomes engulfed in the darkness of deep autumn. The south pole of Titan (3,200 miles across) is near the center of the view. Scientists have long known that the entire winter hemisphere of Titan can exhibit a polar "hood" of haze made of condensing organic compounds, but this is something new and amazing.

Top image: Ron Miller.

Ever since Cassini arrived in the Saturn system in 2004, Titan has had a visible "hood" high above the north pole. It was northern winter at Cassini's arrival, and much of the high northern latitudes were in darkness. But the hood, an area of denser, high altitude haze compared to the rest of the moon's atmosphere, was high enough to be still illuminated by sunlight. The seasons have been changing since Saturn's August 2009 equinox signaled the beginning of spring in the northern hemisphere and fall in the southern hemisphere for the planet and its many moons. Now the high southern latitudes are moving into darkness.

The formation of the vortex at Titan's south pole may be related to the coming southern winter and the start of what will be a south polar hood.

Some scientists think these new images show open cell convection. In open cells, air sinks in the center of the cell and rises at the edge, forming clouds at cell edges. However, because the scientists can't see the layer underneath the layer visible in these new images, they don't know exactly what mechanisms may be at work.


The Cassini team suspects that this maelstrom, clearly forming now over the south pole and spinning more than forty times faster than the moon's solid body, may be a harbinger of what will ultimately become a south polar hood as autumn there turns to winter. The image displays the motion and beautifully detailed cloud patterns — very likely the result of open-cell convection — already visible in this fascinating phenomenon that we on Cassini have been fortunate to capture, for the first time, in the process of being born.

More info at the link. [CICLOPS]