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This review paper summarizes the observations and results of the Mars Express Mission and its application in the analysis of geological processes and landforms on Mars during the last 20 years. The Mars Express observations provided an extended data base allowing a comparative evaluation of different geological surface landforms and their time-based delimitation. High-resolution imagery and digital elevations models on a local to regional scale and spectral measurements are the basis for geological analyses of water-related surface processes on Mars. This includes the nature and discharges of valley networks, formation timescale of deltas, volumina of sedimentary deposits as well as estimating the age of geological units by crater size–frequency distribution measurements. Both the quantifying of geological processes and the determination of absolute model ages allows to constraint the evolution of Martian water-related activity in space and time. Comparative age estimation of fluvial, glacial, and lacustrine deposits, as well as their timing and episodicity, has revealed the nature and evolution of the Martian surface hydrological cycle. Fluvial and lacustrine activity phases are spread over a time span from Noachian until Amazonian periods, but detailed studies show that they have been interrupted by multiple and long-lasting phases of cessation and quiescent. In addition, evidence of glacial activity shows discrete phases of enhanced intensity correlating with increased spin-axis obliquity amplitude. The episodicity of geological processes, erosion, deposition, and glaciation on Mars demonstrate a close correlation between individual surface processes and endogenic activity as well as spin-axis/orbital variations and changing climate condition. [ABSTRACT FROM AUTHOR]

Vermicular Ridge Features (VRFs) comprise a series of ridges and troughs with a circular, sinuous, and anastomosing morphology composed of clast-rich sandy diamict. VRFs were first reported on the south coast of Devon Island, Nunavut, Canada, in the Dundas Harbour region. Here, we document the presence of VRFs near Mokka Fjord on Axel Heiberg Island, Nunavut, Canada. We utilize field observations, ultra high resolution LiDAR, and ground penetrating radar to characterize and compare the morphometry and sedimentology of VRFs near Mokka Fjord to other periglacial, paraglacial, and glacial landforms. VRFs near Mokka Fjord have a diameter ranging from 6 to 37 m and reach up to 1.5 m in height. They comprise clast-rich glaciofluvial sediment and till. A leading periglacial (i.e., segregation ice features/lithalsas) and glacial (i.e., ring-ridge moraines and kame/kettled terraces) origin are presented. We interpret Mokka Fjord VRFs to be an icemarginal feature resulting from paraglacial ablation of buried glacial ice producing a hummocky ring-ridge moraine comprised of ice marginal and supra- and englacial debris. This formation mechanism would infer a largely polythermal glacial environment with limited water supply. Likely from occasional warm-based periods at the ice margins which may allow sediment output and ice burial from basal ice debris redistribution or the thinning and subsequent burial of snout ice from glaciofluvial outwash. [ABSTRACT FROM AUTHOR]