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Before NASA's Cassini spacecraft plunged into the depths of Saturn, it made a final flyby in 2017 of Titan, Saturn's largest moon. This remote world is the only place in the solar system other than the Earth that hosts large masses of standing liquid. Titan liquid is made of methane and ethane instead of water. But these lakes and seas make the moon one of the most interesting places in our solar system. And researchers are just beginning to understand how these liquid bodies change with the seasons of Saturn.
Seasonal changes
Cassini's last visit to Saturn's moon revealed that some of its northern lakes are 300 feet deep, but small in area, and perched on top of high hills. The shape and location of the lakes strongly suggest that the lakes look like karst lakes on the Earth, where liquids gnaw and eventually collapse the surrounding bedrock. On Earth, this happens with water and limestone, but on Titan, it is the liquid methane and the frozen organic matter that make up the superficial layers of Titan. The researchers published their conclusion on April 15 in Nature Astronomy.
In a second study, also published in Nature Astronomy, a different group of researchers has discovered what they call "ghost lakes" on the surface of Titan in the northern hemisphere. These lakes appear in earlier Cassini data and disappear later. Scientists believe that the lakes are shallow, dry and disappear as the seasons change over Titan. A full year of Titan season corresponds to about one Saturnian orbit, or 30 terrestrial years. And since Cassini spent 13 years studying the Saturn system, he offered an excellent perspective to see the northern hemisphere warm up with the beginning of summer, while the southern hemisphere was transformed into winter.
Titan's Icy Slot Canyons Rival Zion National Park
Both studies highlight the complex cycle of Titan methane that scientists are still trying to understand. Like the Earth's water cycle, it moves liquids between the atmosphere, surface and subsoil of Titan, and changes with the seasons and temperatures. This is the only place, apart from Earth, where scientists can observe this complex cycle of liquids on a global scale. They will surely continue to exploit the Cassini data until the time comes for Saturn to welcome a new visitor to the spacecraft.
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