Titan's deep lakes more Earth-like than previously thought
If you're planning to go boating on Saturn's moon Titan, bring your lengthier anchor cables. Based on radar data returned by NASA's Cassini orbiter in April 2017 during its final flyby, researchers have determined that the small methane lakes set on hills in the northern hemisphere of Titan are over 100 m (330 ft) deep, providing new clues as to how Titan's methane-based hydrologic cycle works.
Earth and Saturn's largest moon share some remarkable similarities. Along with having an atmosphere that is 1.45 times the pressure of Earth's, Titan and Earth are the only two bodies in the solar system to have stables liquids on their surfaces, including lakes, streams and seas. True, Titan's are made up of methane and ethane at a temperature of about -179° C (-290 °F), but Titan has is own methane cycle that's analogous to Earth's water cycle, marked by evaporation, cloud formation, rainfall, and runoff into rivers before collecting in lakes and seas.
However, that similarity soon breaks down. While the Earth is dominated by water, Titan has two liquids vying for supremacy. According to NASA, data from Cassini indicates that Ontario Lacus, the only major lake in Titan's southern hemisphere, is made up of equal parts methane and ethane, but the northern lakes are mostly methane.
In addition, there are other distinct regional differences. The eastern hemisphere of Titan shows low-elevation seas, islands, and canyons, but on the western side has small, deep lakes that the Cassini flybys indicate are set atop hills and plateaus high above the Titanic sea level. These landforms jut hundreds of feet above the surrounding landscape, while the lakes plunge hundreds of feet down.
Scientists say that the Titanic lakes being small and deep suggests that they formed as the methane dissolved the bedrock ice and frozen organic compounds. It's a similar process to that found in the karstic lakes of Earth, such as those in Germany, Croatia, and the United States. These are made by the effect of water on soluble rocks like limestone, gypsum and dolomite, which form subterranean caverns that collapse and flood.
"Every time we make discoveries on Titan, Titan becomes more and more mysterious," says Marco Mastrogiuseppe, Cassini radar scientist at Caltech in Pasadena, California. "But these new measurements help give an answer to a few key questions. We can actually now better understand the hydrology of Titan."
The research was published in Nature Astronomy.