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rfmcdonaldJason Major's Universe Today post highlights the latest discovery about Ontario Lacus, a lake in Titan's south polar region that may well be not a permanent body of liquid but rather an intermittent one, a basin that's empty most of the time but fills up when new liquid is introduced, probably precipitation in the case of Ontario Lacus.
I find it amusing that Titan, with its cryogenic environment, is a world that may be too hot for year-round lakes, even in its polar region. Calling Titan an icy desert makes sense.
Ontario Lacus, so named because of its similarity both in shape and size to Lake Ontario here on Earth, was first discovered near the south pole of Titan by the Cassini spacecraft in 2009. Its smooth, dark appearance in radar images indicated a uniform and reflective surface, implying a large — although likely shallow — body of liquid. Of course, on Titan the liquid isn’t water — it’s methane, which is the main ingredient of the hydrologic cycle found on the giant moon. That far from the Sun the temperatures at Titan’s poles fall to a frigid -300ºF (-185ºC), much too cold for water to exist as a liquid and so, on this world, methane has taken its place. A research team led by Thomas Cornet of the Université de Nantes, France has taken a closer look at Cassini’s radar data of Ontario Lacus and found evidence of channels carved into the southern portion. According to the team, this likely indicates that the lakebed surface is exposed. “We conclude that the solid floor of Ontario Lacus is most probably exposed in those areas,” said Cornet. In addition, sediment layers surrounding the lake suggest that the liquid level has varied. All in all, this reveals a striking resemblance between Ontario Lacus and Namibia’s Etosha Pan — an “ephemeral lake” that is dry for much of the year, occasionally filling with a shallow layer of water which evaporates, leaving salty rings of sediment. [. . .] Although Ontario Lacus was initially thought to be permanently filled with liquid hydrocarbons, the team’s findings draw a strong correlation with this well-known Earthly environment, suggesting a much more temporary nature and showing the value of comparative research.Images of Lake Ontario and Ontario Lacus are below.
