Dynamical modelling of river deltas on Titan and Earth

• The dynamical models of formation of river deltas on Titan and Earth are presented.
• Delta morphology produced in model is consistent with terrestrial observations.
• New dimensionless numbers are suggested for description of the process.
• It is found that sediment transport for Titan is more efficient than on Earth.

The surface of Titan hosts a unique Earth-like environment with lakes and rivers, and active ‘hydrologic’ cycle of methane. We investigate sediment transport in Titanian rivers and deposition in Titanian lakes with particular attention to formation of river deltas. The obtained results are compared with analogous terrestrial processes. The numerical model based on Navier–Stokes equations for depth-integrated two dimensional turbulent flow and additional equations for bed-load and suspended-load sediment transport was used in our research. It is found that transport of icy grains in Titanian rivers is more effective than silicate grains of the same size in terrestrial rivers for the same assumed total discharge. This effect is explained theoretically using dimensionless form of equations or comparing forces acting on the grains. Our calculations confirm previous results (Burr et al., 2006. Icarus. 181, 235–242). We calculate also models with organic sediments of different densities, namely 1500 and 800 kg m−3. We found substantial differences between materials of varying densities on Titan, but they are less pronounced than differences between Titan and Earth.