What Summer Is Like on Saturn's Moon Titan

Sorry, beach fans: it's mostly cloudy and the sea is methane.

Aug 15 2014, 2:15pm

Seasonal change on Titan. Image: NASA

For NASA scientists, part of unlocking the mysteries of our solar system is tracking and understanding weather cycles both on and off our own planet. The latest weather news to catch the eye of agency scientists comes from Saturn's largest moon, Titan.

NASA's Cassini spacecraft recently confirmed that clouds are gathering around the moon's north pole, suggesting summer has arrived in the northern hemisphere. The presence of the clouds also provides interesting insight into the planet's climate and large methane seas.

One year on Titan is equivalent to about 30 years on Earth, and each season lasts about seven Earth years. So if the northern hemisphere is just getting into a summer season, observing the clouds and understanding the changes could become a major mission goal for Cassini's final three years. At the moment, the mission is scheduled to end in 2017 with the spacecraft flying to its death towards the heart of the gas giant.

Since its arrival at Saturn in 2004, the Cassini spacecraft has seen cloud activity predominantly around Titan's southern pole; it was late summer in the moon's southern hemisphere at the time. Then, after a huge storm swept through the moon's lower latitudes in 2010, the cloud activity seemed to stop.

It was puzzling to mission scientists, especially since computer models using available data said there should be a lot more weather activity on the distant body. Specifically, models predicted an increase in cloud formation over the north pole as summer reached that hemisphere. The increased cloud cover was expected to bring warmer seasonal temperatures.

The predicted clouds were finally spotted in late July. After a close pass by the moon, Cassini saw clouds developing and dissipating over Titan's northern large methane sea Ligeia Mare, moving between seven and ten miles per hour. It was the first solid evidence that summer might have finally arrived for Titan's northern hemisphere.

"We're eager to find out if the clouds' appearance signals the beginning of summer weather patterns, or if it is an isolated occurrence," said Elizabeth Turtle, a Cassini imaging team associate at the Johns Hopkins University Applied Physics Lab. "Also, how are the clouds related to the seas? Did Cassini just happen catch them over the seas, or do they form there preferentially?"

This GIF shows methane clouds moving above the large methane sea on Titan called Ligeia Mare. Image: CICLOPS

The other reason the cloud patterns on Titan are interesting is because of some similarities between Titan and Earth. Both bodies are similarly inclined to about 26.5 degrees, which means that Titan's methane cycle is quite similar to the water cycle we see on Earth. Titan is also rich in hydrocarbons, the chemical compounds made of hydrogen and carbon that are the basis for life on Earth.

Like we see on Earth, the seasons on Titan brings changes in atmospheric temperatures, chemical composition, and circulation patterns. This is particularly noticeable at the poles where hydrocarbon lakes, like clouds, can develop and dissipate with seasonal changes. 

With conditions and cycles similar to those on our home planet, there's no shortage of compelling reasons to study this distant moon at an interesting time in its year.