TITAN’S CHANNELS: WHAT’S UNDERNEATH?

On Saturn’s moon Titan, methane exists near its triple-point, which allows methane on Titan to play a similar geomorphologic role as does water on Earth. Channels and valley networks on Titan display a range of morphologies that are consistent with fluvial incision caused by methane precipitation, runoff, and erosion of the surface materials. On Earth, careful measurements of channel sinuosities and branching angles reveal slight but significant differences between channels formed in unconsolidated materials (such as alluvial fans, for example) and channels incised into bedrock. Analyses of Titan’s channels and valley networks suggest that the majority of those examined are consistent with forming on a substrate that is neither fully unconsolidated nor fully consolidated. These analyses are consistent with images of Titan’s surface captured by the Huygens Probe Descent Imager/Spectral Radiometer: the images reveal a surface of what appears to be fine-grained (possibly unconsolidated) material that contains rounded to sub-rounded boulders and cobbles. This combination is consistent with the transporting fluids intersecting materials that are massive (such as bedrock) and less consolidated (such as sediment). More morphologic data from well constrained terrestrial streams, as well as computational models, would further constrain the channel substrates on Titan.