Methane lakes on Titan

Saturn has a collection of more than 60 moons, making the planet a kind of mini solar system. Titan is Saturn's largest moon and in many ways similar to earth with weather systems and even lakes (there is even Ontario Lacus, ie. Lake Ontario). The atmosphere is made up of mostly nitrogen and methane, but also has organic molecules with carbon and hydrogen with some oxygen, which are found in our atmosphere, and are needed for life as we know it. 

Methane is a chemical compound. Its chemical formula is CH4. It is the simplest of the saturated hydrocarbons. It consists of four hydrogen atoms and one carbon atom and is the simplest alkane. Methane is lighter than air and only slightly soluble in water.

Lakes on Titan are comprised of methane. And just like our water cycle, the lakes of methane form clouds and even methane rain. In 2005, the European Space Agency’s Huygens spacecraft (part of the Cassini mission) actually pierced the haze and landed on the surface. It revealed a hazy, rocky landscape that has only whetted the appetite for further missions to Titan. The possibility that there were seas on Titan was first suggested based on data from the Voyager 1 and 2 space probes, launched in August and September 1977. The data showed Titan to have a thick atmosphere of approximately the correct temperature and composition to support them. Direct evidence was not obtained until 1995 when data from the Hubble Space Telescope and other observations had already suggested the existence of liquid methane on Titan, either in disconnected pockets or on the scale of satellite-wide oceans, similar to water on Earth. The Cassini mission affirmed the former hypothesis, although not immediately. When the probe arrived in the Saturnian system in 2004, 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. The possibility remained that liquid ethane and methane might be found on Titan's polar regions, where they were expected to be abundant and stable. In Titan's south polar region, an enigmatic dark feature named Ontario Lacus was the first suspected lake identified, possibly created by clouds that are observed to cluster in the area. A possible shoreline was also identified near the pole via radar imagery. Following a flyby on July 22, 2006, in which the Cassini spacecraft's radar imaged the northern latitudes, which were at the time in winter. A number of large, smooth (and thus dark to radar) patches were seen dotting the surface near the pole. Based on the observations, scientists announced "definitive evidence of lakes filled with methane on Saturn's moon Titan" in January 2007. The Cassini–Huygens team concluded that the imaged features are almost certainly the long-sought hydrocarbon lakes, the first stable bodies of surface liquid found off Earth. Some appear to have channels associated with liquid and lie in topographical depressions. Channels in some regions have created surprisingly little erosion, suggesting erosion on Titan is extremely slow, or some other recent phenomena may have wiped out older riverbeds and landforms. Overall, the Cassini radar observations have shown that lakes cover only a few percent of the surface and are concentrated near the poles, making Titan much dryer than Earth. 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.