Ripples in the Water in the Lakes of Titan

Cassini/VIMS image CM 1721848119 1, acquired on the T85 flyby 2012 July 24 from a range of ∼30000km. Credit: Barnes et al. / NASA / JPL / University of Arizona / University of Idaho

Two studies concerning the surface of lakes on Titan have recently been published, and the results show just how varied activity at the Saturnian moon’s surface can be.

The first study comes from Cassini observations of a sea known as Punga Mare, located at Titan’s north pole. Using its Visual and Infrared Mapping Spectrometer (VIMS), Cassini captured reflections of sunlight off of the lake, and the observations show that waves could be rippling across its surface. Another possibility is that the region is filled with mudflats covered by liquid.

If the signals are indeed evidence of waves, it would be the first time that scientists have identified such sea-surface features beyond Earth. It would also support previous theories that the winds in the northern hemisphere of Titan might be picking up as springtime breaks. Right now, the team estimates that the waves could be up to an inch high, but they could get higher as the winds increase.

The study was presented at the 45th Lunar and Planetary Science Conference in The Woodlands, Texas, by lead author Jason Barnes of the University of Idaho (1).

In contrast, a second study using data collected by Cassini in 2013 revealed that the surface of Titan’s second largest sea, Ligeia Mare, is mirror-smooth. The lake, also located in Titan’s north, is most likely filled with liquid methane.

"If you could look out on this sea, it would be really still. It would just be a totally glassy surface," said lead author Howard Zebker in a press release from Stanford University.

This false-color image of the surface of Titan was made using radar measurements made by NASA’s Cassini spacecraft. The spacecraft revealed that the surface of Ligeia Mare, Titan’s second largest lake, is unusually still, most likely due to a lack of winds at the time of observation. Credit: Courtesy of Howard Zebker

Together, the studies provide new insight into seasonal weather patterns on Titan, and could have implications for planning future missions to the moon. NASA and the European Space Agency (ESA) have proposed numerous plans for potential Titan missions, including the Titan Mare Explorer (TiME). TiME was proposed as a lander mission that would collect data while floating in Titan’s hydrocarbon seas.

So far, no mission is scheduled – but a dedicated Titan spacecraft or lander could help astrobiologists determine life’s potential on the unique moon. There is some evidence that Titan supports a subsurface ocean of liquid water, similar to that of Jupiter’s moon Europa. If true, Titan’s subsurface ocean could feasibly support environments for life as we know it. Some scientists have even theorized about the potential for life as we don’t know it on Titan.

Although Titan’s seas are filled with hydrocarbons instead of water, the moon is an active world with some similarities to Earth. Through comparative planetology, studying processes like wind, weather and seasons on Titan can teach astrobiologists about similar processes on Earth.

Happy Birthday to You, Titan

Recently, Titan celebrated its 359th ‘birthday.’ On March 25, 1655, Dutch astronomer Christiaan Huygens discovered Saturn’s second-largest moon, which he called Luna Saturni. The lens from Huygens’ telescope is now on display at the Utrecht University Museum.