Water induced sediment levitation enhances downslope transport on Mars

On Mars, locally warm surface temperatures (~293 K) occur, leading to the possibility of (transient) liquid water on the surface. However, water exposed to the martian atmosphere will boil, and the sediment transport capacity of such unstable water is not well understood. Here, we present laboratory studies of a newly recognized transport mechanism: “levitation” of saturated sediment bodies on a cushion of vapor released by boiling. Sediment transport where this mechanism is active is about nine times greater than without this effect, reducing the amount of water required to transport comparable sediment volumes by nearly an order of magnitude. Our calculations show that the effect of levitation could persist up to ~48 times longer under reduced martian gravity. Sediment levitation must therefore be considered when evaluating the formation of recent and present-day martian mass wasting features, as much less water may be required to form such features than previously thought

Mid-latitude glaciation on Mars

Near-surface water ice, either pure or mixed with regolith, forms a widespread suite of distinctive landforms in Mars’ mid-latitudes. These landforms are in many cases sufficiently similar to cryospheric features on Earth to allow analogue-based comparisons to be made. However, our understanding of glacial processes in Mars’ subpolar latitudes remains far from complete, and crucial fundamental issues remain unresolved. These include basic glaciological information such as the internal physical and thermal structure of martian ice masses, whether (and how) those ice masses move, and the nature of any mass-balance regime they are subject to. Addressing these issues is complicated by the fact that any current knowledge, being based overwhelmingly on the visual interpretation of remotely sensed images, is insufficient to determine the extent to which these landforms are currently active or relict. Addressing these issues would contribute not only to our understanding of Mars’ current landscape but also to our knowledge of Mars’ long-term climatic variability and to our awareness of where and in what form H2O exists on Mars – information that would be of value to future space missions. The aim of this review is to bring the state of knowledge regarding mid-latitude glaciation on Mars to the attention of the wider research community. As background, we provide an overview of the geological and planetary framework within which Mars’ mid-latitude ice was deposited. We then define and describe the various ice-related landforms that have been identified within Mars’ mid-latitudes, and we review the processes that have been proposed to explain the origin and physical characteristics of those landforms. Finally, we present what we consider to be key avenues for further research

Quantifying geological processes on Mars—Results of the high resolution stereo camera (HRSC) on Mars express

This review summarizes the use of High Resolution Stereo Camera (HRSC) data as an instrumental tool and its application in the analysis of geological processes and landforms on Mars during the last 10 years of operation. High-resolution digital elevations models on a local to regional scale are the unique strength of the HRSC instrument. The analysis of these data products enabled quantifying geological processes such as effusion rates of lava flows, tectonic deformation, discharge of water in channels, formation timescales of deltas, geometry of sedimentary deposits as well as estimating the age of geological units by crater size–frequency distribution measurements. Both the quantification of geological processes and the age determination allow constraining the evolution of Martian geologic activity in space and time. A second major contribution of HRSC is the discovery of episodicity in the intensity of geological processes on Mars. This has been revealed by comparative age dating of volcanic, fluvial, glacial, and lacustrine deposits. Volcanic processes on Mars have been active over more than 4 Gyr, with peak phases in all three geologic epochs, generally ceasing towards the Amazonian. Fluvial and lacustrine activity phases spread a time span from Noachian until Amazonian times, but detailed studies show that they have been interrupted by multiple and long lasting phases of quiescence. Also glacial activity shows discrete phases of enhanced intensity that may correlate with periods of increased spin-axis obliquity. The episodicity of geological processes like volcanism, erosion, and glaciation on Mars reflects close correlation between surface processes and endogenic activity as well as orbit variations and changing climate condition