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<\/div>The north polar region of Titan, imaged using radar signals from the Cassini probe, with hydrocarbon seas coloured blue<\/p>\n
NASA \/ JPL-Caltech \/ Agenzia Spaziale Italiana \/ USGS<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Our most detailed look yet at the strange lakes of Saturn\u2019s moon Titan has revealed a diverse seascape, similar to Earth\u2019s combination of freshwater rivers and salty oceans.<\/p>\n
Unlike Earth\u2019s water oceans, Titan\u2019s lakes<\/a> consist of methane and ethane, which are liquid at the planet\u2019s average surface temperatures of about -179\u00b0C (-290\u00b0F).<\/p>\n Radar measurements from NASA\u2019s Cassini spacecraft, which orbited Saturn between 2004 and 2017, have hinted at differences in the lakes\u2019 properties, such as their composition and the waves on their surface. But there wasn\u2019t enough information in the signals to distinguish between them.<\/p>\n Now, Valerio Poggiali<\/a> at Cornell University, New York, and his colleagues have mapped the composition and surface of Titan\u2019s seas using a different radar technique, revealing an increasing amount of ethane as you travel down the planet from its north pole. \u201cThe more north you go, the cleaner and purer the seas are; they\u2019re more methane-dominated,\u201d says Poggiali.<\/p>\n 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.<\/p>\n <\/p>\n The new study analysed signals from Cassini\u2019s radar that had been reflected off the surface of the lakes and then received using radio antennae on Earth operated by NASA, called the Deep Space Network. The shallower angle of the reflected signal meant that it included two kinds of polarised waves, giving Poggiali and his colleagues more information about the lakes\u2019 properties.<\/p>\n They found that many of the rivers and estuaries that fed the lakes had rough surfaces, probably caused by wind-whipped waves. This might be a sign of active tides or currents feeding into the lakes, says Poggiali. \u201cActivity on the surface of the seas is super important if you want to plan a future mission, like a Titan submarine, but also to be able to better understand Titan\u2019s environments in terms of wind and its atmospheric characteristics.\u201d<\/p>\n Poggiali and his colleagues also found that the rivers had a higher composition of methane before they fed the lakes. This could help us track the methane and ethane cycle on Titan, says Ingo Mueller-Wodarg<\/a> at Imperial College London. \u201cWhen a river enters a large, salty ocean on Earth, then you would see that, near where the river enters, you have a lower salinity of the water,\u201d he says. \u201cIt\u2019s kind of a similar thing happening here, only that it\u2019s not about the content of salt, but the relative proportion of methane and ethane.\u201d<\/p>\n Topics:<\/p>\n<\/section><\/div>\n