Post by Dr Mirjam Langhans, Istituto di Astrofisica Spaziale e Fisica Cosmica – INAF, Roma, Italy
Saturn‘s largest moon Titan is one of only a few bodies in the Solar System with an active volatile cycle. Besides Earth, only ancient Mars is supposed to have hosted a water cycle. Titan‘s volatile cycle is based on methane (CH4), occurring in liquid and gaseous state given Titan‘s environmental conditions (e.g. Flasar 1983, Lorenz & Lunine 2005). Despite the different volatiles involved, similar atmospheric processes occur on Titan and Earth, such as the formation of clouds and precipitation .
Following the action of the methane cycle, surface runoff and the incision of linear valleys take place. As a result, fluvial landscapes evolved on Titan, analog to those on Earth (e.g. Tomasko et al. 2005; Perron et al. 2006, Lorenz et al. 2008, Langhans et al. 2012).
Image data obtained during the Cassini-Huygens mission enable the geomorphological analysis of valleys. Although Titan‘s valleys occupy only a small percentage of the surface, they can be found nearly at all latitudes (Langhans et al. 2012). Image 1 shows a network of channels located close to Titan‘s north pole, imaged by Cassini Radar-SAR. The dark tone of the valleys in radar images indicate that they were likely filled with liquids at the time when the image was captured. The valleys in Image 1 end in one of several lakes, situated at high northern latitudes. Image 2 shows valley networks near Titan‘s equator. These valleys provide evidence of fluvial erosion in the past and they are most likely not filled with liquids today due to their bright tone in the radar image.
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