Although the mission of the Cassini-Huygens spacecraft, which explored Saturn and its planetary system, ended nearly seven years ago, the vast amount of data collected over 20 years of research is still being analyzed.

Astronomers from Cornell University have played a significant role in this analysis, and a new study of data obtained from radar experiments has provided new insights into the composition and activity of liquid hydrocarbons in the seas near the north pole of Titan, the largest of Saturn's 146 known moons.

Innovative research method
The bistatic radar experiment involves directing a radio beam from the spacecraft to a target - in this case, Titan - where it is reflected back to a receiving antenna on Earth. This surface reflection is polarized, meaning it provides information collected from two independent perspectives, unlike monostatic radar data, where the reflected signal returns to the spacecraft.

According to Valerio Poggiali, a researcher at the Center for Astrophysics and Planetary Science (CCAPS) at Cornell University, the result of the bistatic method is a more complete data set, sensitive to the composition and roughness of the reflective surface. This new method has allowed scientists to separately analyze the composition and roughness of the surfaces of Titan's seas, which previous analyses of monostatic radar data could not achieve.

Analysis results
The analysis revealed differences in the composition of the surface layers of hydrocarbons in the seas, depending on latitude and location (proximity to rivers and estuaries, for example). The southern part of Kraken Mare showed the highest dielectric constant - a measure of a material's ability to reflect a radio signal. For example, water on Earth is very reflective, with a dielectric constant of about 80; ethane and methane seas on Titan have about 1.7.

Researchers also found that all three seas were mostly calm at the time of the flyover, with surface waves no higher than 3.3 millimeters. Slightly higher roughness - up to 5.2 mm - was detected near coastal areas, estuaries, and inter-basin straits, which are possible indicators of tidal currents.

Valerio Poggiali noted that there are indications that rivers entering the seas contain pure methane until they flow into open liquid seas, which are richer in ethane. This is similar to Earth, where freshwater rivers flow into salty oceans.

Further research
Poggiali stated that further work on the data generated by Cassini during its 13 years of studying Titan is already underway. "There is a mine of data that still awaits to be fully analyzed in a way that should bring new discoveries," he said. "This is just the first step."

Research support
Support for this research was provided by NASA and the Italian Space Agency.

Significance of discoveries
New insights into the composition and dynamics of Titan's seas provide a glimpse into the geological and meteorological processes on this fascinating moon. Differences in the composition of the sea surface layers, revealed by the analysis, depend on latitude and location, indicating complex interactions between atmospheric and surface processes. Especially interesting is the discovery that the southern part of Kraken Mare has the highest dielectric constant, suggesting greater reflectivity of this area.

The research also showed that the sea surfaces are mostly calm, with small waves, which contrasts with the more dynamic conditions we see on Earth. This is important for understanding hydrodynamic processes on Titan and may have implications for future missions and explorations of this moon.

Technical challenges and future steps
Conducting the bistatic radar experiment requires precise coordination between scientists designing it, Cassini mission planners, and the team collecting data at the receiving station. These experiments were conducted during four Cassini flybys in 2014 and 2016, and the data collected during these missions enabled a detailed analysis of Titan's sea surfaces.

Poggiali emphasized the importance of further analysis of the data collected by Cassini during its 13-year mission. "This is just the beginning," he said, pointing out that there is a lot of data that still awaits full analysis. These studies will continue to provide new insights into geological and atmospheric processes on Titan, paving the way for future missions and research.

International cooperation
This research was conducted with the support of NASA and the Italian Space Agency, involving scientists from several global institutions, including the University of Bologna, the Paris Observatory, NASA's Jet Propulsion Laboratory (JPL), California Institute of Technology, Johns Hopkins University Applied Physics Laboratory, and Massachusetts Institute of Technology.

Concluding thoughts
The results of this research provide new insights into the complex processes shaping the surface and atmosphere of Titan. Bistatic radar data allowed for a more detailed analysis of the composition and roughness of the sea surface layers, which will have important implications for future exploration of this fascinating moon. With much data still awaiting analysis, Titan research will continue to uncover new secrets and deepen our understanding of this distant world.

Source: Cornell University