Moon of Saturn has an equivalent of freshwater rivers and salty oceans
The liquid hydrocarbon seas, lakes and rivers on Titan have varying compositions and signs of active tides or currents
By Alex Wilkins
16 July 2024
The north polar region of Titan, imaged using radar signals from the Cassini probe, with hydrocarbon seas coloured blue
NASA / JPL-Caltech / Agenzia Spaziale Italiana / USGS
Our most detailed look yet at the strange lakes of Saturn’s moon Titan has revealed a diverse seascape, similar to Earth’s combination of freshwater rivers and salty oceans.
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Unlike Earth’s water oceans, Titan’s lakes consist of methane and ethane, which are liquid at the planet’s average surface temperatures of about -179°C (-290°F).
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Radar measurements from NASA’s Cassini spacecraft, which orbited Saturn between 2004 and 2017, have hinted at differences in the lakes’ properties, such as their composition and the waves on their surface. But there wasn’t enough information in the signals to distinguish between them.
Now, Valerio Poggiali at Cornell University, New York, and his colleagues have mapped the composition and surface of Titan’s seas using a different radar technique, revealing an increasing amount of ethane as you travel down the planet from its north pole. “The more north you go, the cleaner and purer the seas are; they’re more methane-dominated,” says Poggiali.
Previous radar measurements were made using signals emitted and received at the same location, on the Cassini probe. This meant that the reflected radio waves were polarised, or twisted, in one direction.
