Numerical simulations of areographic formations in comparison with terrestrial surface structures

The surface of Mars exposes a variety of geomorphological features that suggest that on this planet water or ice was once abundant. The channels networks in the oldest parts of the equatorial regions are especially interesting. These valleys, which were most probably formed by liquid water, are well studied, whereas the sedimentary forms caused by fluvial activity were only subject to very few studies. Especially a sedimentary basin in the south eastern part of the Magaritifer Sinus region is of special interest as it exhibits ground textures resembling terrestrial deltas.

In this thesis I develop algorithms and a program package for the simulation of delta formation, based on the topology of the textures under consideration.

The starting point is a pure random model, which was in a more simplified version already the subject of earlier investigations. In this context I develop a variety of analytic-geometrical and topological algorithms. Special emphasis is given to the the generation of random numbers. The resulting model is then compared to the topology derived from thirteen terrestrial deltas.

These experiments lead to the formulation of a semi-empirically physical model for the development of distributary networks. Starting points are the principles of river hydraulics of open channels, an sediment transport model, which I adapted to the given situation, the empirical evidences derived from the deltas, and assumptions concerning a certain degree of randomness. Furthermore only constructive deltas are regarded, as the growth of the distributary systems is simulated.

The new model is then tested on the delta of the river Volga, which has some similarities with the situation of the Magaritifer Sinus basin. Results of the simulations suggest that this semi-empirical physical model is a better approach to delta formation and yields a more convenient explanation of the corresponding surface structures than the random connection model.

An analyzis of the topological characteristics of the Magaritifer Sinus basin is then performed, and the necessary physical parameters for the simulation of the surface structures as seen on the basin floor are derived. It turns out, that the new model yields also a quit plausible explanation for the formation of these areographic structures.

Although more detailed studies are needed to draw final conclusions, the result of this thesis might be seen as another hint to the existence of liquid water on early Mars.

Keywords: Mars, delta distributory networks, river morphology, numerical simulation.
Published: Master’s Thesis, University of Vienna, June 1994.