Dennis Reiss

Deposition and degradation of a volatile‐rich layer in Utopia Planitia and implications for climate history on Mars

[1] We investigate the surface morphology of a study area in western Utopia Planitia, Mars, which is characterized by a variety of landforms that resemble those of terrestrial periglacial landscapes. Polygonally fractured ground and thermokarst-like depressions are found to be located in a young mantling deposit with a thickness of several tens of meters. We observe a latitudinal dependence of the degradation of this mantling deposit. Larger depressions, whose floors reveal the underlying basement rocks, cover a higher fraction of the total terrain in the southern part of the study area than in the northern part, indicating a more intense degradation of the mantle in the south. All depressions have an asymmetric cross section in north-south direction, interpreted to be the result of the different solar radiation on differently oriented slopes. On the basis of our morphological observations, we develop a conceptual model for landscape evolution in western Utopia Planitia. It involves subaerial deposition of a layered, ice-rich mantle and its subsequent degradation by polygon formation and sublimation. A terrestrial analog to the polygonally fractured mantling deposit and its thermokarst-like depressions is the Siberian Ice Complex or ‘‘Yedoma,’’ which consists of subaerial ice-rich deposits and is connected to nonglaciated landscapes with highly continental cold-climatic environmental conditions. Our comparison suggests that no unusual or exotic processes need to be invoked to explain the current morphology of western Utopia. However, the young age of the deposition and degradation implies climatic excursions in the very recent past on Mars.

Landscape evolution in Martian mid-latitude regions: insights from analogous periglacial landforms in Svalbard

Abstract 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 cold-climate 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.

First in‐situ analysis of dust devil tracks on Earth and their comparison with tracks on Mars

In this study we report about the first in-situ analysis of terrestrial dust devil tracks (DDTs) observed in the Turpan depression desert in northwestern China. Passages of active dust devils remove a thin layer of fine grained material (< ∼63 μm), cleaning the upper surface of coarse sands (0.5–1 mm). This erosional process changes the photometric properties of the upper surface causing the albedo differences within the track to the surroundings. Measurements imply that a removal of an equivalent layer thickness of ∼2 μm is sufficient to form the dark dust devil tracks. Our terrestrial results are in agreement with the mechanism proposed by Greeley et al. (2005) for the formation of DDTs on Mars.

Seasonal variations of polygonal thermal contraction crack patterns in a south polar trough, Mars

We present observations of seasonal variations in polygonal crack patterns located in a polar trough on the south polar cap of Mars; previously, there was no direct observation showing that these patterns change. Polygonal patterns on Mars are attributed to thermal contraction cracking, which is commonly observed in periglacial environments on Earth. In this paper we discuss observations based upon the high-resolution image data of the Mars Orbiter Camera and focus on the reconstruction of the seasonal development. The image-based observations are further supported by temperature data. We show that the south polar trough pattern is located in an active geologic unit, which undergoes seasonal variations and annual crack formation. Furthermore, there are strong indications showing these contraction-crack processes take place in a thin layer that might be composed of water-ice and is located beneath the seasonal carbon dioxide ice cover.

Solar panel clearing events, dust devil tracks, and in-situ vortex detections on Mars

Spirit rover solar array data, which if publicly-archived would provide a useful window on Mars meteorology, shows dust-clearing events coinciding with the onset of dust devil season in three Mars years. The recurrence interval of 100-700 days is consistent with the extrapolation of Pathfinder and Phoenix vortex encounters indicated by pressure drops of ~6-40 Pa (similar to laboratory measurements of dust lifting threshold) and with observed areas and rates of generation of dust devil tracks on Mars.

Small rampart craters in an equatorial region on Mars: Implications for near-surface water or ice

Small onset diameters (1 km) of rampart craters were identified in High Resolution Stereo Camera (HRSC) imagery in the equatorial region of the Valles Marineris plateaus. This is in contrast to previous global studies based on Viking imagery, which showed onset diameters in the range of 4 km to 7 km in equatorial regions. The observed small rampart craters show morphologically eroded ejecta blankets. This indicates a formation in the early Martian history, when erosion rates were higher. Volatile rich target material might have been available shortly after the formation of the Hesperian–aged plateaus surrounding Valles Marineris, and this is in agreement with the reported Hesperian fluvial activity in this region. The lack of fresh small rampart craters indicates a lowering of the ground ice table with time.

Water on the Terrestrial Planets

Water is the second most abundant molecule in our solar system, following only molecular hydrogen. It plays an important role in many planetary processes and has significant importance for the habitability of a planetary body. Despite the importance of water, its complex physical behavior is still only partly understood.