Glacial and fuvial evolution of landforms in Hellas Planitia, Mars

Kurzfassung

The focus of this thesis is the geospatial analysis of both fluvial and glacial landforms in Hellas Planitia Mars. The ancient impact structure contains the deepest point on the surface, and hence, the highest air pressure. Its interior is among the places with the highest likelihood for the transient existence of liquid water and the highest protection against solar radiation (both with implications for potential past or present habitability). The investigation of landforms with respect to their geographical distribution, evolution, and mutual relation, is essential for any attempt to link form to process, i.e. to reconstruct climatic conditions through the study of surface morphology. In order to quantify the distribution of 24 pre-selected landforms in Hellas Planitia, the so-called grid-mapping method has been applied; i. a. for glacier-like flows, gullies, sheet deposits, and latitude-dependent ice-dust deposits. The results provided evidence about possible clockwise-rotating wind circulation systems within Hellas Planitia. Moreover, a lack of glacial features and gullies in the lowest parts of the basin has been detected; despite the high air pressure potentially allowing water to be liquid. The systematic search at high-resolution scale did also not reveal clear evidence for extensive shoreline morphologies as suggested by several authors; hence a hypothesized lake within Hellas Planitia could not be confirmed. Among others, grid-mapping revealed widespread lobate sheet deposits at the lower reaches of Dao Vallis in eastern Hellas Planitia (being one of the big outflow channels draining into the basin). Similar features have already been interpreted in several regions of the planet as either volcanic or fluvial origin. Assessing both scenarios, a water-related formation is more likely, as most surface features can be better explained by fluvial rather than volcanic processes. The result is consistent with other stratigraphic findings and formation scenarios of the related Dao Vallis system. This work revealed that Hellas Planitia has always been a matter of environmental change. While there is many evidence for fluvial activities during all Martian epochs (e. g., light-toned deposits, channels, gullies), there are also several indications of glacial activities (glacier-like flows or viscos-flow features). However, the results of this work do not support the existence of a lake within that vast depression. This thesis has demonstrated that grid mapping is a very helpful and effective method for quantifying the distribution of landforms over huge areas, revealing information and relations about climate and landscape evolution, which are only visible from a much wider perspective; from ancient Noachian to very recent Amazonian landforms. For future research this approach can also be applied to other terrestrial bodies and space missions.