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Although the present environmental conditions on Mars prohibit the generation of significant volumes of liquid water, observations of several very young landforms, such as gullies and recurrent slope lineae, have been interpreted as signals for aqueous processes. To explore the range of conditions under which such features can be formed on Earth, a field site in northern Victoria Land, East Antarctica, was geomorphologically investigated. Despite the small size of the icefree area, the site displays gullies, water tracks and other traces of liquid water. The gullies show clear evidence of sediment transport by debris flows, and are typical of paraglacial processes on steep slopes in a recently deglaciated area. Water tracks appear in different forms, and seem to recur seasonally in the austral summer. Melting of snow and surface glacier ice is the major water source for both debris flows and water tracks. The observations presented here highlight the potential for hyperarid polar deserts to generate morphogenetically significant amounts of meltwater. The gullies are morphologically analogous to Martian gullies, and water tracks on steep slopes appear very similar to recurrent slope lineae. The observations suggest that even small icefree sites in continental Antarctica may enable observations which can serve as a basis for working hypotheses in Mars analogue studies, and future field work should consider more areas in Antarctica in addition to the McMurdo Dry Valleys to search for Mars analogue landforms.

The existence of solifluction lobe-like landforms on Mars may, potentially, have important implications for our understanding of the distribution of thaw liquids and its geomorphic effects in recent climate history. In this study we made an inventory of all HiRISE images between 40°S-80°S acquired between 2007 and 2013 and show their distribution and their close spatio-temporal relationship to other ice-related landforms such as gullies and polygons. Based on Earth-analog studies and landscape analysis we conclude that a hypothesis of freeze/thaw may better explain their origin then current ”dry” models.

Polygonally fractured ground is widespread at middle and high latitudes on Mars. The latitude-dependence and the morphologic similarity to terrestrial patterned ground in permafrost regions may indicate a formation as thermal contraction cracks, but the exact formation mechanisms are still unclear. In particular, it is debated whether freeze-thaw processes and liquid water are required to generate the observed features. This study quantitatively investigates polygonal networks in ice-free parts of continental Antarctica to help distinguishing between different hypotheses of their origin on Mars. The study site is located in the Helliwell Hills in Northern Victoria Land (�71.73�S/161.38�E) and was visited in the framework of the GANOVEX XI expedition during the austral summer of 2015/2016. The local bedrock consists mostly of sediments (sandstones) of the Beacon Supergroup and mafic igneous intrusions (Ferrar Dolerites). The surfaces are covered by glacial drift consisting of clasts with diverse lithologies. Thermal contraction cracks are ubiquitous.We mapped polygons in the northern part of Helliwell Hills in a GIS environment on the basis of high-resolution satellite images with a pixel size of �50 cm. The measured spatial parameters include polygon area, perimeter, length, width, circularity and aspect.We also analyzed the connectivity of enclosed polygons within a polygon network. The polygons do not display significant local relief, but overall the polygon centers are slightly higher than the bounding cracks (i.e. high-center polygons). Sizes of polygons can vary widely, dependent on the geographical location, between 10m2 and >900m2. In planar and level areas, thermal contraction cracks tend to be well connected as hexagonal or irregular polygonal networks without a preferred alignment. In contrast, polygonal networks on slopes form elongated, orthogonal primary cracks, which are either parallel or transverse to the steepest topographic gradient. During fieldwork, excavations were made in the center of polygons and across the bounding cracks. Typically, the uppermost �40 cm of regolith are dry and unconsolidated. Below that, there is commonly a sharp transition to ice-cemented material or very clear ice with no bubbles. Soil profiles were recorded, and sediment samples were taken and analyzed for their grain size composition with laser diffractometric measurement methods. External factors such as slope gradient and orientation, insolation and composition of surface and subsurface materials were included in the analysis.

To understand and quantify processes by which ice-cored lateral moraines degrade we propose a methodology, which derives daily backwasting rates from georeferenced High Resolution Orthoimages (HRO) and correlates them with in situ meteorological data. This approach aims to increase the accuracy of backwasting rate measurements and seeks to identify relevant parameters for the degradation rate of ice-cored moraines. This study further compares daily backwasting rates to the exact area of scarp retreat to investigate which measurable parameter is best suited to determine the rate of the degradation process. A thaw slump on the southwestern side of Kongsfjorden (Svalbard) was analyzed between 2 and 6 August 2014, which is during the melting season. We determined daily backwasting rates between 0.04 and 0.33 m/day (0.20 m/day on average) during the four day long observation period. These results are normalized values, which consider the overall size of the thaw slump. The area of scarp retreat varied from 1.51 to 4.37 m2/day (3.00 m2/day on average). On the basis of Time Lapse Imagery (TLI) and the analysis of in situ meteorological data, we observed positive correlations between backwasting and increasing ground temperatures and the occurrence of precipitation events. We revisited the study area in the beginning of August 2016 and documented an area of scarp retreat of 186 m2 and �13 m of backwasting within two years, which equals to a minimal daily backwasting rate of about 0.07 m/day. The average value is estimated to be higher, because our observations indicate that thaw slump activity already ceased before we revisited the study area. Our methodology requires longer observation periods in order to draw firm conclusions, but its results have a low relative error of about 4 % and are normalized to the thaw slump size. Therefore, we suggest this as an appropriate approach to document and quantify degradation ice-loss processes in periglacial environment.

We present landforms on Svalbard (Norway) as terrestrial analogs for possible Martian periglacial surface features. While there are closer climatic analogs for Mars, e.g., the Antarctic Dry Valleys, Svalbard has unique advantages that make it a very useful study area. Svalbard is easily accessible and offers a periglacial landscape where many differ- ent landforms can be encountered in close spatial proximity. These landforms include thermal contraction cracks, slope stripes, rock glaciers, protalus ramparts, and pingos, all of which have close morphological analogs on Mars. The combination of remote- sensing data, in particular images and digital elevation models, with fi eld work is a promising approach in analog studies and facilitates acquisition of fi rst-hand experi- ence with permafrost environments. Based on the morphological ambiguity of certain landforms such as pingos, we recommend that Martian cold-climate landforms should not be investigated in isolation, but as part of a landscape system in a geological context.

We compared the morphology of gully sedimentary fans on Svalbard as possible analogs to gullies on Mars in order to constrain whether fl uvial and/or debris-fl ow processes are predominantly responsible for the formation of Martian gullies. Our analysis is based on high-resolution imagery (High Resolution Stereo Camera [HRSC-AX], ~20 cm/pixel) acquired through a fl ight campaign in summer 2008 and ground truth during two expeditions in the summers of 2008 and 2009 in Svalbard, compared to high-resolution satellite imagery (High Resolution Imaging Science Experiment [HiRISE], ~25 cm/pixel) from Mars. On Svalbard, fl uvial and debris-fl ow processes are evident in the formation of gullies, but the morphological characteristics clearly show that the transport and sedimentation of eroded material are predominated by debris fl ows. Most investigated gullies on Mars lack clear evidence for debris-fl ow processes. The Martian gully fan morphology is more consistent with the deposition of small overlapping fans by multiple fl uvial fl ow events. Clear evidence for debris fl ows on Mars was only found in one new location, in addition to a few previously published examples. The occurrence of debrisfl ow processes in the formation of Martian gullies seems to be rare and locally limited. If predominantly fl uvial processes caused the formation of gullies on Mars, then large amounts of water would have been required for their formation because of the relatively low sediment supply in stream and/or hyperconcentrated fl ows. Repeated seasonal or episodic snow deposition and melting during periods of higher obliquity in the recent past on Mars can best explain the formation of the gullies.

Periglacial landforms on Spitsbergen (Svalbard, Norway) are morphologically similar to landforms on Mars that are probably related to the past and/or present existence of ice at or near the surface. Many of these landforms, such as gullies, debris-flow fans, polygonal terrain, fractured mounds and rock-glacier-like features, are observed in close spatial proximity in mid-latitude craters on Mars. On Svalbard, analogous landforms occur in strikingly similar proximity, which makes them useful study cases to infer the spatial and chronological evolution of Martian coldclimate surface processes. The analysis of the morphological inventory of analogous landforms on Svalbard and Mars allows the processes operating on Mars to be constrained. Different qualitative scenarios of landscape evolution on Mars help to better understand the action of periglacial processes on Mars in the recent past.