A group of researchers led by planetary scientist Dr Jason Barnes have announced that they have found evidence of waves on Punga Mare, the third largest lake on Saturn’s moon Titan. Titan is the second largest moon in the solar system, after Jupiter’s moon Ganymede. It is even larger than Mercury, and has an orbit that takes 30 terrestrial years.
If this report is correct, it will be the first time that waves have been detected anywhere other than Earth. By closely studying images captured in 2012 by the spacecraft Cassini, which is in orbit around Saturn, the researchers identified regions of the lake that did not reflect like a perfect plane would. Further investigation revealed that the light being received by Cassini is similar to what would be expected from two centimeter high waves. Such waves would be produced by a wind of about 0.79 metres per second.
Dr Barnes is quick to point out that these results are not conclusive, but only very good indicators that there is wave activity on Titan. He suggests, for instance, that mud flats covered by a layer of hydrocarbons could produce a similar observation. Nevertheless, the reported waves offer support to a popular hypothesis that winds in Titan’s northern hemisphere undergo a seasonal cycle, and should be picking up as it moves from winter to spring.
Titan is a fascinating and surprisingly Earth-like world. There is no liquid water on its 93 K surface–although some mountains are made of frozen ice rather than rock or dust. But it has all of the rivers, lakes and precipitation of Earth; the only difference is that Titan’s liquid is made up of hydrocarbons, primarily methane and ethane. All told, there are some 8 000 cubic kilometres of liquid hydrocarbons on Titan’s surface, hundreds of times more than the proven reserves of Earth.
Scientist hope that they will be able to make even more discoveries about Titan in the coming years as its seasons shift. For instance, they are curious to see how much hydrocarbons migrate away from the warmer summer hemisphere, where more evaporation occurs, to the colder winter hemisphere, where more precipitation occurs. Currently, 29 of Titan’s 32 major lakes are in the Northern Hemisphere, including Purga Mare. Only one–Ontario Lacus, so named because it is similar in size to Lake Ontario–is located near the south pole. It is expected that as the northern hemisphere moves towards summer, the lakes of the south side will begin to grow and northern ones shrink as the liquid migrates southward.
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