Since the Cassini spacecraft arrived in Saturn space back in 2004, it’s sent back a steady stream of science and astounding imagery from this amazing system. Perhaps the most tantalizing have been data on Saturn’s largest moon Titan, which sports an atmosphere and a strange environment of water ice and methane. Now, the formation of an enormous cloud over the moon’s south pole suggest that things might be changing.
According to NASA, Cassini has observed a similar “shroud” of clouds (cloud shroud?) over Titan’s north pole since it arrived eight years ago. The seasons on Titan are tied to Saturn’s 30-year orbit around the sun, and scientists think that the formation of a vortex over the south pole could signal the end of summer in that hemisphere and the coming of winter. Notably, Saturn passed through its equinox about three years ago, further bolstering the suspicions of a seasonal change.
The vortex is forming as the southern regions of Titan darken, creating cooler regions in the atmosphere. The vortex is thought to be similar to Titan’s north pole “hood” of high, dense clouds. While NASA scientists think they have a good idea of what’s happening, they can’t be entirely sure. From the Cassini Imaging Central Laboratory for Operations:
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 what mechanisms may be at work.
That we can see this view at all is thanks to a change recently made in Cassini’s orbit. Originally, Cassini orbited along Saturn’s equator, but has moved into a new configuration as part of its extended “solstice” mission.
Careful readers will recall that the clouds on Titan are formed through its complex, and somewhat mysterious, methane cycle. In our post on the moon’s equatorial methane lakes, we noted how liquid methane in these regions generally evaporates and travel toward the cooler poles where it condenses. Presumably, these polar shrouds are part of that same process.
Titan has proved to be a real gem in the long-running Cassini mission, churning out many new discoveries about the moon this year alone. Hopefully with an extended mission for Cassini, we’ll learn even more about this weird little world by the ringed planet.
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