Planetary scientists have found what they believe are the first liquid waves to be detected on another body besides Earth. Images of Punga Mare, a 380-km wide sea on Titan, which is Saturn’s moon, contains telltale signs of isolated rippling. Unlike Earth’s waves of water, the seas on Titan are composed of hydrocarbons such as ethane and methane. The temperature at Titan’s surface is an average of approximately -180C, which causes the hydrocarbons to be found in a liquid state.
The new findings were discussed by the scientist behind them, Jason Barnes, of the University of Idaho, at the 45th Lunar and Planetary Science Conference (LPSC), which was held this week in Texas. Barnes describes Titan as a type of bizarro-Earth because although it does have a significant atmosphere, a change of seasons, albeit with a 30-year seasonal cycle, wind, and rain, the topography shaped by the winds and rain are composed of ice, and liquid hydrocarbons take the place of water in most cases.
Titan contains a large number of lakes and seas, but repeated imaging of Saturn’s moon has shown only still surfaces, a finding which has baffled scientists who believed that given the dense atmosphere of Titan, some type of weather, such as wind and rain, would exist to disturb the surface of so much liquid. Not only that, but the gravitational force of 1/7 of that of Earth’s offers little resistance to the formation of waves. However, during its 90 passes by Titan since 2004, the Cassini probe detected no movement on the surface of Titan’s seas.
It was only while images from Cassini that were taken of Titan’s north pole in 2012 and 2012 were being reviewed by scientists that they detected that sunlight was being reflected off of liquid on the surface, a phenomenon called a specular reflection.
Dr. Barnes used mathematical models to determine if waves were what was causing sunlight to reflect. Although he states that there could be other possibilities for the cause of the phenomenon on Titan, he reiterated that it is the belief of both himself and his team, which includes scientists from several research institutions such as MIT, Cornell, and JPL, that they have discovered what are the first waves that are not on Earth.
If Barnes is correct and Titan does have waves, they are present in only a few places in Punga Mare and have a slope of six degrees. In order to create those types of waves, wind would have to be blowing at a speed of approximately .75 m/s, which puts the height of the waves at a paltry 2cm high. The discovery of waves on Titan may help to explain other imaging anomalies in its other liquid bodies that have been captured over the years. As Titan’s seasons change, the wind speeds are expected to increase, which will cause bigger waves to form.
Titan’s northern region is expected to reach its summer solstice in 2017. If the increased wind creates waves, Cassini should have the ability to detect and capture them through imaging. Knowing the dimensions of waves could help to reveal which chemicals make up the lakes and seas on Titan. The speed of waves would correspond to the speed of the winds above, which would help scientists to refine and verify their research on the climate on Titan.
By Jennifer Pfalz