Scientists Observe A Change In Season's On Moon Titan For First Time

The seasons are changing and not just on Earth - scientists at NASA are reporting signs that Titan, Saturn's largest moon, is currently in flux.

The researchers report that an ice cloud is taking shape over the its south pole similar to the one that has long hung over its northern pole, which is now fading, according to observations made by the Composite Infrared Spectrometer (CIRS) on the Cassini spacecraft.

"We assocaite this particular kind of ice cloud with winter weather on Titan, and this is the first time we have detected it anywhere but the north pole," said the study's lead author, Donald E. Jenning, in a press release.

And while scientists don't know what either ice clouds are composed of, their observations have led them to believe that an important pattern of global air circulation on Titan has reversed its direction.

Despite being the first time the phenomenon has ever been observed, scientists have long predicted the circulation reversal once Titan's north pole began to warm and its south pole to cool. In fact, the official transition from winter to spring at the north pole began nearly four years ago. In all, each season on Titan is the equivalent of seven to eight Earth years. 

The first visual signs of the reversal came in 2012 when Cassini images and visual and infrared mapping spectrometer data showed a high-altitude "haze hood" and a swirling polar vortex at the south pole, both of which have long been associated with the colder north pole. 

Despite these changes, the ice cloud had yet to form, however.

"This lag makes sense, because first the new circulation pattern has to bring loads and loads of gases to the south pole," Carrie Anderson, a CIRS team member, said. "Then the air has to sink. The ices have to condense. And the pole has to be under enough shadow to protect the vapors that condense to form these ices."

And while Titan may be a celestial object far different from Earth, researchers say there's a lot to learn from watching the changes currently taking place.

"What's happening at Titan's poles has some analogy to Earth and to our ozone holes," said CIRS Principal Investigator F. Micahel Flasar. "And on Earth, the ices in the high polar clouds aren't just window dress: They play a role in releasing the chlorine that destroys the ozone. How this affects Titan chemistry is still unknown. So it's important to learn as much as we can about this phenomenon, wherever we find it."