Titan

Liquids on Titan

It has long been believed that lakes or even seas of methane might exist on Titan's surface but until recently, conclusive evidence has proven elusive.[27] When the Cassini probe arrived in the Saturnian system, it was hoped that hydrocarbon lakes or oceans might be detectable by reflected sunlight from the surface of any liquid bodies, but no specular reflections were initially observed. Cassini observed surface features that could be explained as the products of flowing liquids, but again, there were few conclusive observations.

The first indication of the presence of a lake was observed at Titan's south pole, where clouds have been observed to cluster, and where an enigmatic dark feature at the pole, named Ontario Lacus was identified as a possible lake created by precipitation from them.[28] A possible shoreline has also been identified at the pole via radar imagery.[29] Then, on January 3, 2007, it was announced that scientists have "definitive evidence of lakes filled with methane on Saturn's moon Titan."[30][31] The high relative humidity of methane in Titan’s lower atmosphere could be maintained by evaporation from lakes covering only 0.002–0.02 of the whole surface [32].

Following a flyby on July 22, 2006, in which the Cassini spacecraft's radar imaged the northern latitudes (which are currently in winter), a number of large, dark (and thus smooth to radar) patches were seen dotting the surface near the pole.[33] The Cassini-Huygens team have now concluded that these features are almost certainly the long sought hydrocarbon lakes of Titan. Some of the lakes appear to have channels running in or out of them, which are just as smooth. Ethane and methane may be liquids near Titan's poles, which are cold enough for these gases to condense. Repeated coverage of these areas should prove whether they are truly liquid, as any changes that correspond with wind blowing on the surface of the liquid would alter the roughness of the surface and be visible in the radar. NASA recently confirmed that there is ice from hydrocarbon rain at the north polar area.