NASA’s Cassini spacecraft, which concluded its mission by plunging into Saturn in 2017, continues to provide valuable data from its exploration of Saturn and its moons. Recent analysis of Cassini’s radar observations has unveiled intriguing details about the seas on Titan, Saturn’s largest moon and the second-largest in our solar system.
Titan is unique in our solar system, aside from Earth, in having liquid seas on its surface. However, these seas are composed not of water but of methane and ethane, key components of natural gas. Cassini’s data focused on three large seas near Titan’s north pole: Kraken Mare, Ligeia Mare, and Punga Mare. Kraken Mare, the largest, covers an area comparable to the Caspian Sea. Ligeia Mare is similar in size to Lake Superior, while Punga Mare is roughly the size of Lake Victoria.
The study found that the chemical composition of these seas varies with latitude, with some areas being more methane-rich and others more ethane-rich. Additionally, Cassini’s radar detected ripples on the sea surfaces, suggesting the presence of active tidal currents, especially near estuaries where rivers meet the seas.
Titan’s atmosphere, rich in nitrogen, creates a unique hydrologic system where methane rains down from clouds, flows into rivers, and collects in seas. This system mirrors Earth’s water cycle, albeit with different chemicals due to Titan’s cold climate. The data indicates that rivers on Titan carry pure liquid methane, which mixes with the more ethane-rich sea waters, similar to how Earth’s freshwater rivers merge into saltwater oceans.
The study utilized bistatic radar data from Cassini, collected during flybys of Titan in 2014 and 2016. This method provided detailed information about the sea surfaces, including their roughness and composition. According to Valerio Poggiali, lead author of the study published in Nature Communications, this dataset is likely the last untouched data from Cassini, offering fresh insights into Titan’s landscape.
Titan’s environment is considered a potential site for studying prebiotic chemistry, which could provide clues about the origins of life. The moon’s complex organic chemistry, combined with the possibility of a subsurface ocean of liquid water, makes it a compelling subject for further study. Poggiali and his colleagues are particularly interested in whether the heavy organic molecules produced in Titan’s atmosphere have interacted with liquid water, potentially leading to the development of life.
