Sandstone outcrops seen with the ExoMars PanCam emulator

Post by Dr. Peter Fawdon, (@DrPfawdon) School of Physical Sciences, The Open University, United Kingdom

PanCam (Coates et al., 2017) is the imaging instrument on the 2020 ExoMars rover and consists of two wide angle cameras; (WAC’s) and a High Resolution Camera (HRC). PanCam will be used to lead the geological characterisation of the local area outcrops. It will be used to establishing the geological setting of outcrops and identify targets for subsurface sampling and analysis with the ExoMars drill and suite of analytical instruments (Vago et al., 2017).

An emulator for the ExoMars PanCam instrument has been used in rover operation field trials in southern Spain. The aim of these trials has been to explore how scientists will use the instruments in rover missions. These images, taken by the emulator, are examples of what PanCam data might look like and show how the PanCam images will be used (e.g., Harris et al., 2015).

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Image 1: PanCam Multi-spectral images: (A) A colour composite made from the red, green and blue filters shows a ridge named ‘Glengoyne’ at approximately 20 m distance from the rover. (B) A Multi spectral image using the geology filters stretched to emphasise the variation in the scene.

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Universality of delta bifurcations

Post by Dr. Robert C. Mahon, Department of Earth and Environmental Science, University of New Orleans

Which morphologic features of sedimentary systems persist into the stratigraphic record? Ancient river deltas preserved as stratigraphic deposits on both Earth and Mars exhibit remarkable morphologic similarities to modern deltas on Earth (Images 1-3). While channel dynamics may be expected to alter the geomorphic expressions of past channel networks, in many cases channel bodies appear to be preserved in their original configurations. Fully understanding the ways in which geomorphic features become preserved as stratigraphy can provide tools for us to both infer past processes from the ancient deposits with greater confidence, as well as to predict the geometries of ancient deposits in the subsurface (i.e. for resource exploration).

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Image 1: CTX image mosaic of a delta in the Aeolis region of Mars, showing distributary channel networks. CTX imagery courtesy of NASA-MRO/JPL/UA.

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The Largest Delta on Mars?

Post by Jacob Adler, School of Earth and Space Exploration, Arizona State University.

Ancient river deltas are found in many locations on Mars [see Di Achile & Hynek, 2010 and references therein], and are formed as sediment drops out of suspension in water as it approaches a wider shoreline of a lake, sea, or (debatably) an ocean. Some proposed deltas on Mars are found in closed basins (e.g. an impact crater) away from the Martian dichotomy boundary, implying an ancient climate during which the crater ponded with water [e.g. Eberswalde or Jezero]. Occasionally, inlet and outlet river valleys are seen at different elevations along the crater rim, lending further evidence to the hypothesis that the crater filled with liquid water at least up to the outlet elevation. Deltas found in open basins, on the other hand, imply a larger body of standing water, and Mars scientists look for other clues to support the deltaic rather than alluvial fan formation mechanism. In our recent papers, we tested whether the Hypanis fan-shaped deposit (Image 1) could be a delta, and discussed whether this supports the hypothesis that there was once a large sea or ocean in the Northern plains of Mars [Adler et al., 2018; Fawdon et al., 2018].

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Image 1: a) The Hypanis deposit stands out as light-toned in the center of this Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) mosaic of our study region. Also marked are Lederberg crater, and the Sabrina deposit in the closed basin of Magong crater. (b) Hypanis and Sabrina have a low nighttime temperature (dark) as recorded by the THEMIS instrument on Mars Odyssey, suggesting it is mostly composed of small grain size material. Image from the Nighttime IR 100m Global Mosaic v14.0 [Hill et al. (2014); Edwards (2011)] and from the Northern Hypanis Valles Night IR Mosaic [Fergason (2009)]. NASA/JPL/ASU. (c) Our proposed fluvial sequence discussed in the paper. Main lobe (A) could once have had continuous layered beds spanning to the distal island deposits (E). The cross-cutting relationships we observed are consistent with hypothesized shoreline regression to the north. Flow migrated to the northern lobe (B), then to braided inverted channels (C and D) as water retreated. NASA/MSSS/USGS. d) Our digital elevation mosaic shows the topography of Hypanis and surrounding features. Elevations are colored from white (-2500 m) to light green (-2800 m).

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Measuring Cross-Bed Geometry in Upper Aeolis Mons, Gale Crater, Mars

Post by Dr. Ryan B. Anderson, Astrogeology Science Center, United States Geological Survey

One of the most environmentally diagnostic features of sedimentary rocks is cross-bedding, which occurs when sediment is transported by wind, water, or volcanic processes, resulting in horizontal strata composed of inclined beds. The geometry of cross-bedded sedimentary deposits provides information about the depositional setting and post-depositional history of the rocks, making the identification, measurement, and interpretation of cross-beds particularly interesting on Mars, where past conditions are of great scientific interest. This post describes cross-bedding in Upper Aeolis Mons in Gale crater (Image 1).

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Image 1: Example of complex bedding patterns in upper Aeolis Mons, interpreted to be large-scale aeolian cross beds. Image is an inset of HiRISE observation PSP_001620_1750.

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Stepped Fans and Phyllosilicates on Mars

Post by Peter Grindrod, Natural History Museum, London, UK.

A number of different studies have catalogued features on Mars that could be given the general heading of sedimentary fans [e.g. Irwin et al., 2005; Kraal et al. 2008]. These features occur whenever the velocity of a river or stream decreases, and the water no longer has enough energy to carry its sediment, and thus begins to deposit its load. This drop in energy often occurs when the water flows into flatter and wider regions. The distribution of these fans on Mars is important because it shows the location of past water flows, and the amount of material that has been transported (which can be used as a proxy for flow duration).

However, one of the fundamental problems when looking at these features with orbital data alone, is that it is difficult to determine whether the river flowed into a standing body of water (for example a lake) or just an empty canyon or crater. Of course, the implications of this problem are important if we want to understand the volume and distribution of past water on Mars, which in themselves feed into understanding the past climate and even habitability of Mars.

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Image 1: Location of the two fans in Coprates Catena, SE Valles Marineris. MOLA elevation overlain on THEMIS daytime image.

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Geologically recent glacial melting on Mars

Post by Frances. E. G. Butcher, School of Physical Sciences, Open University, UK.

Thousands of putative debris-covered glaciers in Mars’ middle latitudes host water ice in volumes comparable to that of all glaciers and ice caps on Earth, excluding the Greenland and Antarctic ice sheets (Levy et al., 2014). These glaciers formed within the last 100 million to 1 billion years of Mars’ geological history (Berman et al., 2015), a period that is thought to have been similarly cold and hyper-arid to present-day Mars. This is broadly corroborated by a sparsity of evidence for melting of these geologically ‘young’ mid-latitude glaciers, which suggests that they have always been entirely frozen to their beds in ‘cold-based’ thermal regimes, and haven’t generated meltwater (e.g. Marchant and Head, 2007). Nevertheless, this months’ planetary geomorphology image provides evidence for melting of one such glacier.

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Image 1: An esker emerging from the tongue of a debris-covered glacier in Tempe Terra, Mars. See Image 2 for an annotated 3D view of this scene. The dashed white line delineates the terminus of the debris-covered glacier, which occupies the southern and eastern portions of the image. The white arrow marked A indicates the first emergence of the crest of the esker ridge from the glacier surface. The white arrow marked A’ indicates the northernmost end of the esker ridge in the deglaciated zone beyond the ice terminus. Context Camera image P05_002907_2258_XN_45N083W (Malin et al., 2007). Modified from Butcher et al., 2017 under a Creative Commons license CC BY 4.0.

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Enigmatic Clastic Polygons on Mars

Post by Laura Brooker, Open University, Milton Keynes, UK.

Polygonal ground of centimetre- to decametre-scale is one of the most common features found in cold-climate regions on Earth and on Mars. Polygonal shapes on Earth can form through a number of different processes including the thermal contraction of ice-cemented soils, forming fracture patterns known as thermal contraction polygons, through the freezing and thawing of ground ice moving clasts, in the case of sorted patterned ground, or through the dehydration of volatile-rich material, termed desiccation polygons. Around a large crater found in the northern latitudes of Mars, named Lyot, we observe stunning and unusually large clastic polygons (Image 1), but how do they form? To understand landforms on Mars we turn to analogues on Earth and compare morphological data to look for similarities and differences.

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Image 1: HiRISE (ESP_016985_2315) image of clastic polygonal ground observed to the north east of Lyot crater, Mars. These enigmatic polygons are demarcated by clastic material in their borders and are averagely 130 metres in diameter. Image credit: NASA/JPL/University of Arizona.

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Creepy stuff – possible solifluction on Mars

Post contributed by Andreas Johnsson, Department of Earth Sciences, University of Gothenburg, Sweden.

Small-scale lobes on Mars (Fig. 1) are tens to hundreds of meters wide and consist of an arcuate frontal riser that is a meter to meters in height and a tread surface (Johnsson et al., 2012) (Fig. 2). The riser is often, but not always, outlined by clasts visible at HiRISE resolution (50-25 cm/pixel; McEwen et al., 2007). They are found on crater slopes in the martian middle and high latitudes in both hemispheres (e.g., Gallagher et al., 2011; Johnsson et al., 2012; 2017) .

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Figure 1. Subset of HiRISE image PSP_008141_2440 (lat: 63.78°N/long: 292.32°E) showing multiple clast-banked lobes in an unnamed 16-km diameter crater (white arrow). Note the degraded gully system (black arrows) and lobes inside the alcove area.

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Small martian landslides – are they similar to large landslides on Earth?

Post contributed by Susan J. Conway and Anthony Guimpier, CNRS Laboratoire de Planétologie et Géodynamique à Nantes, France.

Landslides have been documented on almost all the solid bodies of the solar system and Mars is no exception. The most famous landslides on Mars are the giant landslides in the Valles Marineris, which were discovered in the images returned by the first Mars Orbiter “Mariner 9” launched in 1971 (Lucchitta, 1979). They have volumes typically ranging from 108-1013 m3 (McEwen 1989; Quentin et al. 2004; Brunetti et al. 2014) and have been found to have occurred periodically since the canyon’s formation 3.5 billion years ago (Quantin et al. 2004). The largest size of terrestrial landslides generally only extends to 108 m3 (McEwen 1989; Quentin et al. 2004).

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Image 1: Oblique views of small landslides on Mars. Top: Landslide in Chyrse Choas in HiRISE image PSP_005701_1920 draped over 2 m/pix elevation model. Crater just in front of the landslide is 70 m in diameter and the landslide from crest to toe spans 900 m in elevation. The largest boulders are nearly 40 m in diameter. Bottom: Landslide in Capri Chasma in HiRISE image ESP_035831_1760 draped over 2 m/pix elevation model. Crater on slope is 270 m across and the landslide from crest to toe spans ~1 km of elevation. The largest boulders are just over 30 m in diameter.

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Terraced Craters Reveal Buried Ice Sheet on Mars

Post contributed by A.M. Bramson, Lunar and Planetary Laboratory, University of Arizona

When an object impacts into layered material, it can form a crater with terraces in the crater’s walls at the layer boundaries, rather than the simple bowl-shape that is expected. The shock wave generated by the impact can more easily move the weaker material and so the crater is essentially wider in that layer, and smaller in the underlying stronger material. From overhead, these concentric terraces give the appearance of a bullseye. Craters with this morphology were noticed on the moon back in the 1960s with the terracing attributed to a surface regolith layer. More recently, numerous terraced craters have been found across a region of Mars called Arcadia Planitia that we think is due to a widespread buried ice sheet.

 

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Image 1: A terraced crater with diameter of 734 meters located at 46.58°N, 194.85°E, in the Arcadia Planitia region of Mars. This 3D perspective was made by Ali Bramson with HiRISE Digital Terrain Model DTEEC_018522_2270_019010_2270_A01. Using this 3D model, we were able to measure the depth to the terraces, and therefore the thicknesses of the subsurface layers that cause the terracing.

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The subsurface as the key to surface on Martian gullies

Post by Dr. T. de Haas, Department of Geography, Durham University.

Martian gullies are composite landforms that comprise an alcove, channel and depositional fan. They are very young geological features, some of which have been active over the last million years. Water-free sediment flows, likely triggered by CO2 sublimation, debris flows, and fluvial flows have all been hypothesized to have formed gullies. These processes require very different amounts of liquid water, and therefore their relative contribution to gully-formation is of key importance for climatic inferences. Formative inferences based on surface morphology may be biased however, because of substantial post-depositional modification (Images 1-3).

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Image 1: Morphometry, morphology and stratigraphy of depositional landforms in Galap crater. (a) Overview and digital elevation model of Galap crater. (b) Detail of northwestern slope showing gradients of catchment and depositional fan. (c) Detail of proximal fan surface. (d) Detail of distal fan surface. (e) Detail of fan surface with incised channels; the dashed line indicates the rockfall limit. (f) Example of stratigraphic section. (h) Same stratigraphic section as in f, but with optimized contrast in the section. Arrows denote downslope direction. HiRISE image PSP_003939_1420.

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Everything you wanted to know about martian scoria cones, but were afraid to ask…

Post contributed by Dr. Petr Brož, Institute of Geophysics of the Czech Academy of Science

Volcanism is an important process which shapes the surfaces of all terrestrial planets, and is still active on Earth, Jupiter’s moon Io, and perhaps on Venus. On Earth, volcanoes with wide variety of shapes and sizes exist; however, the size of volcanoes is anti-correlated with their frequency, i.e. small volcanoes are much more numerous than large ones. The most common terrestrial volcanoes are represented by kilometre-sized scoria cones (Figure 1a). These are conical edifices of pyroclastic material originating from explosive volcanic activity. Degassing of ascending magma causes magma fragmentation on eruption piling up the pyroclasts around the vent as a cone. Interestingly, scoria cones as known from Earth, have not been observed commonly on any other terrestrial body in the solar system despite the fact that magma degassing, and hence magma fragmentation, has to occur on these bodies as well.

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Figure 1: Example of a terrestrial scoria cone (panel a, Lassen Volcanic National Park, California, photographed by the National Park Service) and its putative martian analogue (panel b, detail of CTX image P22_009554_1858_XN_05N122W).

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The Geomorphology of Potential Mars Tsunami Deposits

Post by Dr. Alexis Rodriguez. Planetary Scientist, Planetary Science Institute, Tucson, AZ, USA.

The Martian northern lowlands are thought to currently be extensively covered by an ice-rich deposit, interpreted by some researchers to be the residue of an ancient ocean that existed ~3.4 Ga (Kreslavsky and Head., 2002). However, evidence for this ocean has remained a subject of intense dispute and scientific scrutiny since it was first proposed (Parker et al., 1989, 1993) several decades. The controversy has largely stemmed in the fact that the proposed Martian paleo-shoreline features exhibit significant elevation ranges (Head et al., 1999), a lack of wave-cut paleoshoreline features (Malin and Edgett, 1999), and the presence of lobate margins (Tanaka et al., 1997, 2005).

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Fig. 1. Left: Color-coded digital elevation model of the study area showing the two proposed shoreline levels of an early Mars ocean that existed approximately 3.4 billion years ago. Right: Areas covered by the documented tsunami events extending from these shorelines. Lead author Alexis Rodriguez created this figure.

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Water, water, everywhere…?

Post contributed by Dr. Susan J. Conway CNRS and LPG Nantes, France

The similarity of water-formed landforms on Earth is often used as a key argument for the involvement of liquid water in shaping the surfaces of other planets. The major drawback of the argument is “equifinality” whereby very similar looking landforms can be produced by entirely different processes. A good illustration is leveed channels with lobate deposits (Image 1). Such landforms can be built on Earth by wet debris flow, lava flow, pyroclastic flows and they are also found on Mars (de Haas et al., 2015; Johnsson et al., 2014) where the formation process is debated.

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Image 1: Lobes and levees, scale bars are 50 m in all cases. Wet debris flow deposits in Svalbard, image credit DLR HRSC-AX campaign. Lava flows on Tenerife, aerial image courtesy of IGN, Plan Nacional de Ortofotografía Aérea de España. Self-channelling pyroclastic deposits at Lascar volcano, Chile, Pleiades image. Depositional lobes in Istok crater on Mars, HiRISE image PSP_007127_1345.

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Large aeolian ripples on Mars

Post contributed by Dr. Ryan C. Ewing, Department of Geology and Geophysics, Texas A&M University

Ripples cover the surfaces of sand dunes on Earth and Mars. On Earth, ripples formed in typical aeolian sand (e.g., 0.1 and 0.3 mm) range in wavelength between 10 and 15 cm and display a highly straight, two-dimensional crestline geometry. Ripples are thought to develop through a process dominated by the ballistic impacts of saltating sand grains in which wavelength selection occurs through the interplay of grain size, wind speed, the saltation trajectories of the sand grains, and ripple topography.

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Figure 1: Wind-blown impact ripples from Mesquite Flat Sand Dunes, Death Valley, USA. Pen is ~15 cm. Inferred transport direction is to the right on the image. Image credit: Ryan C. Ewing

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Debris-Covered Glaciers on Earth and Mars

Post contributed by David P. Mayer, Department of Geophysical Science, the University of Chicago

Debris-covered glaciers are glaciers whose ablation zones are at least partially covered by supraglacial debris. On Earth, debris-covered glaciers are found in all major mountain glacier systems. The debris itself is primarily derived from rockfall above the accumulation zone. This material becomes entrained in the accumulating ice and is carried englacially before emerging in the ablation zone. On Mars, numerous mid-latitude landforms have been interpreted as debris-covered glaciers based on their geomorphic similarity to nearby ice-rich landforms such as lobate debris aprons (LDA), as well as their similarity to terrestrial debris-covered alpine glaciers (Head et al., 2010 and refs. therein).

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Image 1: Aerial photo of Mullins Glacier in Beacon Valley, Antarctica, a debris-covered glacier and possible analog to certain landforms on Mars. USGS aerial photo TMA 3080/275. Available from http://www.pgc.umn.edu/imagery/aerial/antarctica.

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The surface expression of intrusive volcanic activity on Mars

Post contributed by Peter Fawdon, Dept. of Earth and Planetary Sciences, Birkbeck, University of London, UK.

Volcanism is an important process that can be observed on the surface of many planetary bodies. Not all magma bodies erupt extrusively onto the planet’s surface, many simply stall within the crust, cooling slowly over millions of years to form igneous intrusions. On Earth erosion and uplift expose the frozen core of ancient volcanoes relatively frequently, however, it is considerably more difficult to investigate this intrusive magmatism on other planets.

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Figure 1 shows a perspective view across Nili Patera. This view is generated in ArcScene using data from a mosaic of three CTX elevation models and orthoimages. The view shows Nili Tholus and the associated bright central lava unit as well as the graben along the top of the uplifted region of the western caldera floor.

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Martian Maars: valuable sites in the search for traces of past martian life

Post contributed by Dr. Sandro Rossato, Department of Geosciences, University of Padova, Padova, Italy

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Figure 1: Terrestrial maars. (a) is a group of three maars filled with water in the Eifel region, Germany (rim-to-rim diameter ~0.5-1 km) (“Maare” by Martin Schildgen – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons – https://commons.wikimedia.org/wiki/File:Maare.jpg#/media/File:Maare.jpg). (b) shows the Wabah maar, located in Saudi Arabia (rim-to-rim diameter ~2 km) (courtesy of Vic Camp, San Diego State University).

Terrestrial maar-diatremes are small volcanoes (see this previous post for a general description) which have craters whose floor lies below the pre-eruptive surface and are surrounded by a tuff ejecta ring 2-5 km wide (Figure 1) that depends on the size of the maar itself and on the depth of the explosion (Lorenz, 2003). Maar-diatremes constitute highly valuable sites for in situ investigations on planetary bodies, because they expose rocks at the surface from a great range of crustal depths and are sites which could preferentially preserve biomarkers.

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Sedimentology and Hydrology of an Amazonian paleo-fluivo-lacustrine systems on Mars (Moa Valles)

Post contributed by Francesco Salese from IRSPS/Dipartimento INGEO, Università D’Annunzio, Pescara, Italy.

Mars, is one of the planetary bodies where water flowed and where it may transiently flow today under certain conditions. Many martian paleodrainage systems and well-preserved fluvial and lacustrine deposits have been recognized and studied in the last two decades (see further reading). Widespread dendritic valley networks and the presence of extensive fluvial features on ancient martian terrains suggest that a relatively “warm and wet” climate was prevalent early in the planet’s history (about 3.7 Ga). This is in stark contrast with the hyper-arid, extremely cold climate that is thought to have persisted from 3 Ga until the present (Amazonian Era). The subject of this post is Moa Valles [Salese et al., 2016], which is a 2 billion year old paleodrainage system (Figure 1) that is nearly 300 km long and is carved into ancient highland terrains of Tempe Terra in the northern hemisphere of Mars. Understanding the origin and evolution of this type of complex and interconnected paleo-fluvio-lacustrine system is critical for understanding the early martian climate.

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Figure 1: The upper panel shows the THEMIS-VIS daytime mosaic of Moa Vallis system.The lower panel is a line drawing showing the channel system in blue lines, red dotted lines represent wrinkle ridges, the drainage basin is delimited in grey, and fan-shaped and deltaic deposits in orange. The total mapped length of the channel as shown here is ~325 km, and the flow direction is towards the east.

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Inverted wadis on Earth: analogs for inversion of relief on the Martian surface

Post contributed by Abdallah S. Zaki, Department of Geography, Ain Shams University.

The evolution of inverted topography on Earth and Mars can result from surface armouring of the channel, infilling of channels/valleys by lava flows, and cementation of valley floor by secondary minerals (such as, calcium carbonate, gypcrete, ferricrete, calcrete) – see post by Rebecca Williams. This post specifically concerns inverted wadis, which have been identified in a number of localities on Earth, including multiple localities in the Sahara and Arabia, Australia, the Ebro Basin of Spain, Utah, and New Mexico and west Texas (e.g., Miller, 1937; Maizels, 1987; 1990). Inversion of relief is observed commonly on Mars, for example, Eberswalde Crater, Arabia Terra, Juventae Chasma, Olympus Mons, and Antoniadi Crater (e.g., Pain et al., 2007; Williams et al., 2007).

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Image 1: Google Earth image of the dendritic pattern preserved in inverted wadis in eastern Saudi Arabia.

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Salty Flows on Mars!

Post contributed by Lujendra Ojha, Georgia Institute of Technology.

Recurring slope lineae (RSL) are dark, narrow features forming on present-day Mars that have been suggested to be a result of transient flowing water. RSL extend incrementally downslope on steep, warm slopes, fade when inactive, and reappear annually over multiple Mars years (Images 1 and 2). Average RSL range in width from a few meters (<5 m), down to detection limit for the High Resolution Imaging Science Experiment (HiRISE) camera (~0.30 m/pixel). The temperatures on slopes where RSL are active typically exceed 250 K and commonly are above 273 K. These characteristics suggest a possible role of salts in lowering the freezing point of water, allowing briny solutions to flow.

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Image 1: RSL flowing downhill on the steep slopes of Palikir crater in the southern mid-latitude of Mars. Credits: NASA/JPL/University of Arizona.

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Groundwater outflow on Mars – insights from large-scale experiments

Post contributed by Dr. Wouter Marra, Faculty of Geosciences, Universiteit Utrecht.

There are many water-worn features on the planet Mars, which contribute to the reconstruction of former hydrological conditions. For example, dendritic valley networks show that there was precipitation in the Noachian, the oldest epoch on Mars more than 3.7 billion years ago (Craddock and Howard, 2002). In contrast, fluvial morphologies in younger terrains seem to originate from groundwater (e.g. Baker and Milton, 1974). These are valleys that appear suddenly in the landscape, for example the large outflow channels (e.g. Mangala Vallis and Kasei Vallis) and theatre-headed valleys (such as Nirgal Vallis). However, such systems and their implications are poorly understood. To better understand the formation of such landscapes, I performed several scale-experiments focused on the fundamental process and resulting morphology.

Image 1: Landscapes formed by seepage of groundwater. Left are photos from the experiments, right are examples of Martian cases. Top images show seepage from a distal source, characterized by many small valleys in between large valleys as result of flow convergence to the large valleys. Bottom images have a local source of groundwater, which results in the formation of many valleys of similar size. Arrows indicate (inferred) flow direction. Martian images are from THEMIS daytime infrared.

Image 1: Landscapes formed by seepage of groundwater. Left are photos from the experiments, right are examples of Martian cases. Top images show seepage from a distal source, characterized by many small valleys in between large valleys as result of flow convergence to the large valleys. Bottom images have a local source of groundwater, which results in the formation of many valleys of similar size. Arrows indicate (inferred) flow direction. Martian images are from THEMIS daytime infrared.

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Valleys, Deltas, and Lacustrine Sediment in the South-western Melas Basin, Valles Marineris, Mars

Post contributed by Joel Davis, Department of Earth Sciences, University College London, UK.

During the last few decades, dry river valley networks and delta fan structures have been found to be increasingly common on ancient terrains on the martian surface (e.g. Goldspiel and Squyres, 1991; Hynek et al., 2010). They are considered to be one of the main lines of evidence that Mars once had Earth-like precipitation and surface runoff (e.g. Hynek and Phillips, 2003). One such location is the south-western Melas basin, part of a collapsed graben structure on the southern wall of Melas Chasma, Valles Marineris – Mars’ equatorial canyon system (Images 1 & 2). The basin likely formed in the early Hesperian period (~ 3.7 – 3.5 Ga), soon after Melas Chasma opened.

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Image 1: Context Camera image-mosaic of western portion of palaeolake sequence in the south-western Melas basin. In the left of the image, valley networks can be seen converging on a delta-like structure at the centre of the image. Layered lacustrine deposits are well exposed in the right of the image; about 40-50 packages are visible at this resolution. [Image numbers: G22_026866_1710_XN_09S077W & P07_003685_1711_XI_08S076W]

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Possible Periglacial landscape in Utopia Planitia, Mars

Post contributed by Alex Barrett, Dept. of Physical Sciences, Open University, UK.

The following images show the walls of a two kilometre diameter impact crater in Utopia Planitia on Mars. This region is part of the low lying Northern Plains which have generally flat topography. The main occurrences of steeper hill slopes in this region are impact craters such as the one illustrated below.

Image 1: This image shows the southern wall of a two kilometre diameter impact crater in Eastern Utopia Planitia.

Image 1: This image shows the southern wall of a two kilometre diameter impact crater in Eastern Utopia Planitia. Note that the image has been rotated so that down-slope is towards the bottom of the image. Several rows of lobate structures can be seen on the right hand side of the image. These may be analogous to the solifluction lobes found in periglacial environments on Earth. To the left hand side of the image are several thin lines of metre scale clasts which could possibly be sorted stripes.

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Dust Storms in Hellas Planitia, Mars

Post by Mr Martin Voelker and Dr. Daniela Tirsch, Institute of Planetary Research, German Aerospace Center, Berlin.

In July 2012 the Context Camera (CTX) on board Mars Reconnaissance Orbiter (MRO) observed an upcoming and well-defined dust storm in a giant impact basin in the southern hemisphere on Mars known as Hellas Planitia. Although this deep lowland is notable for its dust storms, this image shows a unique view of a nascent storm system; from its first gusts to its shredded front.

Image 1: Dust storm event in eastern Hellas Planitia. The white area at the left of the image is the east-west trending wrinkle ridge. Note the helical currents in its southern part and the flow front in the very north (CTX image D02_027836_ 1333_XN_46S272W). Image credit: NASA, JPL, Malin Space Science

Image 1: Dust storm event in eastern Hellas Planitia. The white area at the left of the image is the east-west trending wrinkle ridge. Note the helical currents in its southern part and the flow front in the very north (CTX image D02_027836_ 1333_XN_46S272W). Image credit: NASA, JPL, Malin Space Science

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Long-runout landslide transport in Valles Marineris, Mars

Post contributed by Jessica Watkins, Dept. of Earth, Planetary, and Space Sciences, University of California, Los Angeles, USA.

Long-runout (> 50 km) subaerial mass movement is rare on Earth but it is one of the most prominent geomorphic processes shaping Valles Marineris in equatorial Mars. It has occurred widely and nearly continuously within the canyon system over the past 3.5 billion years (Quantin et al., 2004).

Image 1: Long-runout landslide in Ius Chasma, Valles Marineris, with characteristic zoned morphology. Blue box indicates location of spectral map in Image 3. Image is Thermal Emission Imaging System (THEMIS) daytime infrared mosaic. Image credit: NASA/JPL/ASU

Image 1: Long-runout landslide in Ius Chasma, Valles Marineris, with characteristic zoned morphology. Blue box indicates location of spectral map in Image 3. Image is Thermal Emission Imaging System (THEMIS) daytime infrared mosaic.
Image credit: NASA/JPL/ASU

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Diverted landslides in Valles Marineris

Post contributed by Dr Peter Grindrod, Department of Earth and Planetary Sciences, University of London

Layered deposits on Mars are a globally-pervasive record of the sedimentary history of the planet. These deposits not only preserve long sequences of Mars’ stratigraphic record, but also exhibit evidence for hydrous minerals and aqueous activity, and thus help to define the habitability through time. Layered deposits are therefore high priority exploration targets for current and future missions, including the Mars Science Laboratory Curiosity Rover, which currently sits at the base of an interior layered deposit (ILD) in Gale Crater.

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Image 1. A typical landslide in Valles Marineris, Mars. CTX DTM made at the UK NASA RPIF (Regional Planetary Image Facility) at University College London. Images B21_017688_1685_XN_11S067W and B22_018321_1685_XN_11S068W. Image credit: NASA/JPL/Malin Space Science Systems.

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Gullies and ice on Mars.

Post by Dr Susan Conway, Open University, UK

Gullies on Mars were first discovered in 2000 (Malin and Edgett, 2000) in images taken by the Mars Orbiter Camera on board NASA’s Mars Global Surveyor platform. They are kilometre-scale features and have a striking resemblance to water-carved gullies on Earth (Image 1).

Image 1: Example of gully morphologies on Mars in HiRISE data. Image credits: NASA/JPL/UofA. (a) Gullies on the wall of a small impact crater within Kaiser crater, image number: PSP_003418_1335. (b) gullies within a polar pit, image number: PSP_003498_1090. (c) Gullies on the wall of Galap crater, near Sirenum Fossae, image number: PSP_003939_1420 (d) Gullies on the wall of Wirtz crater, a large impact crater to the east of Argyre basin, image number: PSP_002457_1310 (e) Gullies on the slip face of dunes in Russell Crater in Noachis Terra, image number: PSP_001440_1255 (f) Gullies on the wall of an impact crater to the west of Newton Crater in Terra Sirenum, image number: PSP_005930_1395.

Image 1: Example of gully morphologies on Mars in HiRISE data. Image credits: NASA/JPL/UofA. (a) Gullies on the wall of a small impact crater within Kaiser crater, image number: PSP_003418_1335. (b) gullies within a polar pit, image number: PSP_003498_1090. (c) Gullies on the wall of Galap crater, near Sirenum Fossae, image number: PSP_003939_1420 (d) Gullies on the wall of Wirtz crater, a large impact crater to the east of Argyre basin, image number: PSP_002457_1310 (e) Gullies on the slip face of dunes in Russell Crater in Noachis Terra, image number: PSP_001440_1255 (f) Gullies on the wall of an impact crater to the west of Newton Crater in Terra Sirenum, image number: PSP_005930_1395.

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Very recent debris flow activity on Mars

Post contributed by Dr Andreas Johnsson, Department of Earth Sciences, University of Gothenburg, Sweden.

The question whether Martian gullies formed by fluvial processes or by dry mass wasting have been a source of heated debate ever since their discovery (Malin and Edgett, 2000). Intense research within the last decade however points to a fluvial origin for a majority of gully landforms on Mars.

Image 1. A) Overview of the pole-facing interior crater wall (PSP_006837_1345). B) Clearly defined paired levee deposits (white arrows). C) Multiple overlapping lobate deposits (white arrows). D) Gully fan dominated by debris flows (white arrows). E) Well defined medial deposit (debris plug) (white arrow).  Image credit: NASA/JPL/UofA for HiRISE.

Image 1. A) Overview of the pole-facing interior crater wall (PSP_006837_1345). B) Clearly defined paired levee deposits (white arrows). C) Multiple overlapping lobate deposits (white arrows). D) Gully fan dominated by debris flows (white arrows). E) Well defined medial deposit (debris plug) (white arrow). Image credit: NASA/JPL/UofA for HiRISE.

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Liquid Water and Water Ice on Gale Crater, Mars

Post by Dr. Alberto G. Fairén, Dept. of Astronomy, Cornell University, USA, and Centro de Astrobiología, Spain.

Gale crater, the site of the currently active Mars Science Laboratory (MSL) or Curiosity Rover mission, is a ~154-km-diameter impact crater formed during the Late Noachian/Early Hesperian at the dichotomy boundary on Mars (Cabrol et al., 1999; Anderson and Bell III, 2010; Wray, 2013). The northern floor and rim of Gale are ~1–2 km lower in elevation than its southern floor and rim, and the crater shows a layered central mound named Aeolis Mons, which is 100 km wide, extends over an area of 6000 km2, and is up to 5 km in height (Malin and Edgett, 2000).

Image 1: Details of the lobate features, arcuate ridges and terminal moraines in the central mound of Gale.

Image 1: Details of the lobate features, arcuate ridges and terminal moraines in the central mound of Gale.

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Experimental Delta Formation in Crater Lakes

Post by G. de Villiers, Faculty of Geoscience, Utrecht University.

Fan-shaped deposits have been identified on the surface of Mars (Image 1). These sediment bodies often occur within impact craters and, specifically in the cases of fan deltas, suggests that these craters were once lakes early in Martian history. Fan delta morphologies are indicative of upstream (e.g. flow discharge and sediment properties) and downstream (e.g. basin characteristics) parameters, from which the hydrological conditions at the time of formation can be inferred (e.g. Kleinhans et al. 2010).

IAGFigure1

Image 1: Examples of fan delta deposits on Mars, formed in enclosed impact crater or rift basins. A) Single-scarped, branched prograding delta (PSP_006954); B) Single-scarped, smooth prograding delta (I10805012); and C) Multiple-scarped, stepped retrograding delta (V17040003). White line is approximately 5 km.

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Megaflood on Mars from a Breached Crater Lake

Post by Dr Neil Coleman, University of Pittsburgh.

A group of Martian craters formerly contained lakes, some of which overtopped and breached the crater rims to cause flooding and channel erosion.

Image 1:  View of Morella Crater and the complex of Elaver Vallis channels eroded by floodwaters released when the crater rim was breached.  The distal reaches of Elaver Vallis were obliterated by the southward expansion of Ganges Chasma, which is 5 km deep.  The chasma as seen today did not exist during the Elaver flood, otherwise high groundwater pressures would have been relieved by breakouts in the walls and floor of the chasma [graphic is a mosaic of THEMIS daytime infrared (IR) images].

Image 1: View of Morella Crater and the complex of Elaver Vallis channels eroded by floodwaters released when the crater rim was breached. The distal reaches of Elaver Vallis were obliterated by the southward expansion of Ganges Chasma, which is 5 km deep. The chasma as seen today did not exist during the Elaver flood, otherwise high groundwater pressures would have been relieved by breakouts in the walls and floor of the chasma [graphic is a mosaic of THEMIS daytime infrared (IR) images].

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An ancient glacial system in Valles Marineris, Mars

Post by O. Bourgeois, M. Gourronc, D. Mège and S. Pochat – Laboratoire de Planétologie et Géodynamique, Université de Nantes, France

The current climate on Mars does not allow for significant accumulations of surface ice at low latitudes. Therefore ice is only found at the two polar ice caps and in a number of ice-filled craters scattered at northern and southern latitudes (> 70°).

Image 1 :  Extent of Late Noachian – Early Hesperian glaciation and location of supraglacial landslides in Valles Marineris (Gourronc et al., 2014).

Image 1 : Extent of Late Noachian – Early Hesperian glaciation and location of supraglacial landslides in Valles Marineris (Gourronc et al., 2014).

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Ancient Lake Deposits on Mars

Post by Tim Goudge, Department of Geological Sciences, Brown University, Providence, RI

There is much morphologic evidence that there was flowing water on the surface of Mars early in its history. Such evidence includes fluvial channels and valleys, often termed valley networks, (e.g., Pieri, 1980; Irwin, 2005a; Fassett and Head, 2008a) as well as paleolake basins that are fed by these valley networks (e.g., Goldspiel and Squyres, 1991; Cabrol and Grin, 1999, 2001; Irwin et al., 2005b; Fassett and Head, 2005, 2008b).

Image 1. Exposed layered deposit of probable lacustrine origin within an open-basin lake (-27.7°N, 76.1°E). Inset image (indicated by red box in main image) shows detailed layering within the exposed deposit. Main image is from the Context Camera (CTX) instrument (image number B02_010338_1518_XI_28S282W; ~5 m/pixel), and inset image is from the High Resolution Imaging Science Experiment (HiRISE) instrument (image number PSP_010338_1525; ~50 cm/pixel).

Image 1. Exposed layered deposit of probable lacustrine origin within an open-basin lake (-27.7°N, 76.1°E). Inset image (indicated by red box in main image) shows detailed layering within the exposed deposit. Main image is from the Context Camera (CTX) instrument (image number B02_010338_1518_XI_28S282W; ~5 m/pixel), and inset image is from the High Resolution Imaging Science Experiment (HiRISE) instrument (image number PSP_010338_1525; ~50 cm/pixel).

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Slope Streaks on Mars

Post by Dr Norbert Schörghofer, University of Hawaii, Honolulu.

Slope streaks are a form of down-slope mass movement on the surface of Mars that frequently occurs on Mars today (Image 1 and 2). Slope streaks were first identified on high-resolution Viking Orbiter images, but their present-day activity was only discovered in Mars Orbiter Camera (MOC) images.

Image 1. A portion of a Mars Orbiter Camera image taken on 1999-10-28.

Image 1. A portion of a Mars Orbiter Camera image taken on 1999-10-28.

Image 2: An Image of the same area taken on 2002-06-10. A large new slope streak formed, while numerous other streaks persisted. North is up and illumination is from the lower left (Schorghofer et al. 2007).

Image 2: An Image of the same area taken on 2002-06-10. A large new slope streak formed, while numerous other streaks persisted. North is up and illumination is from the lower left (Schorghofer et al. 2007).

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Paleolakes on Mars

Post by Dr. Gino Erkeling, Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Germany

The hypothesis of ancient Martian standing bodies of water, which might have occupied the lowlands of the northern hemisphere and which might have existed in local- to regional-scale paleolakes once in Martian history, is one of the most important subjects of ongoing discussion in Mars research (e.g., Parker et al., 1989, 1993; Head et al., 1999; Cabrol and Grin, 1999, 2001; Clifford and Parker, 2001; Kreslavsky and Head, 2002; Carr and Head, 2003; Ghatan and Zimbelman, 2006; Di Achille and Hynek, 2010; Mouginot et al., 2012). The case for large standing bodies of liquid water, including lakes, seas and oceans, is attributed to a complex hydrologic cycle that may have once existed on Mars in the Noachian (>3.7 Ga) and perhaps also in the Hesperian (>3.1 Ga).

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Fluvial channels in Central Pit Craters

Post by Samantha Peel Department of Earth and Planetary Sciences, University of Tennessee, USA.

Central pit craters are a crater type that contain an approximately circular depressions in their floor or central peak (Image 1). These craters have been found on Mars, Ganymede, and Callisto (e.g., Barlow, 2010; Alzate and Barlow, 2011; Bray et al., 2012). On Mars, a subset of central pit craters has been found to contain valleys that terminate in central pits (Peel and Fassett, 2013). These “pit valleys” are believed to have formed as ancient rivers transported water and sediment to the central pits.

Image1

Image 1: Mosaic of three MRO CTX images (B18_016770_1429_XI_37S201W, B19_017192_1443_XI_35S202W, B19_016981_1432_XN_36S201W) showing the interior of a well-preserved central pit crater with pit valleys. The crater is located at 36.30ºS, 158ºE.

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Recent vents and channels on the Cerberus plains of Mars: lava or water?

Posted by Rebecca Thomas, Department of Physical Sciences, The Open University, UK.

Recent channelized flows from vents in the Cerberus plains of Mars demonstrate the difficulties of uniquely ascribing process to landforms on other planets.  The image below shows two fissures emanating from a wrinkle ridge. Both fissures appear to be sources of approximately contemporaneous channels running down onto the surrounding plains (Thomas, 2013). The channel in the west is constructive and differs from that in the east which is clearly shows several phases of incision (Image 1).

Image 1: a. Vents and channels in the Cerberus plains, Mars (156.9° E, 7.1° N); b. incised channel; c. constructed, leveed channel. (HiRISE ESP_016361_1870)

Image 1: a. Vents and channels in the Cerberus plains, Mars (156.9° E, 7.1° N); b. incised channel; c. constructed, leveed channel. (HiRISE ESP_016361_1870)

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Young gullies and their relationships to the dust-ice mantle on Mars

Posted by Jan Raack, Institut für Planetologie, WWU Münster, Germany

Image 1: Smooth appearing atmospherically derived dust-ice mantle on a south-west facing mountain slope. The flow direction of the gullies is from north to south. The gullies only erode the dust-ice mantle; the underlying bedrock was not substantially eroded. A modified dust-ice mantle  indicates as viscous flow features(black arrows) are visible at the termini of the aprons. Subscene of CTX-image P05_003170_1331_XI_46S050W

Image 1: Smooth appearing atmospherically derived dust-ice mantle on a south-west facing mountain slope. The flow direction of the gullies is from north to south. The gullies only erode the dust-ice mantle; the underlying bedrock was not substantially eroded. A modified dust-ice mantle indicates as viscous flow features(black arrows) are visible at the termini of the aprons. Subscene of CTX-image P05_003170_1331_XI_46S050W

Gullies are erosional-depositional landforms consisting of a source area (alcove), channel and apron. They occur primarily on mountain slopes and on crater walls on Mars. Morphologic attributes such as braided channels, point bars, and cut banks in many gullies suggest that fluvial processes were involved in their formation. The most plausible agent to form gullies is liquid H2O (groundwater seepage, melting of near surface ice and snow, or melting of a dust-ice layer on the surface). Alternative gully formation processes on Mars include the sublimation of CO2 or dry granular flows. Gullies have a wide range of ages and age determinations by crater size-frequency distribution measurements (a method used in planetary science to date surfaces via the size and frequency of impact craters) show that gullies on Mars were active in the past few million years. (more…)

Closed (hydrostatic) pingos on Earth and possibly Mars

Post by Drs. Richard Soare, Susan Conway and Peter Grindrod

Closed-system (hydrostatic) pingos (CSPs) are perenially ice-cored (non-glacial) mounds formed primarily by the near-surface injection of pore water. Their shape ranges from circular and sub-circular to elongate and their size varies from a few to hundreds of metres in diameter. Some of them reach tens of metres in height (see Figs. 1a,b).

Image 1 Plan view of a thermokarst lake/closed-system pingo assemblage that lies 6 km sw of Tuktoyaktuk on the coast of the Beaufort Sea in northern Canada (690,26’,34” N, 1330,01’,52” W). Ibyuk Pingo, at the right, is ~48 m high; Split Pingo, at the centre, is ~38 m high. Both pingos display irregular cavities at their summits. These are markers of mound degradation. Image A27917- 35-1993, courtesy of the National Air Photo Library, Ottawa, all rights reserved. Arrow indicates approximate viewing direction of part b. b. Ground view of Split Pingo (at the right) and Ibyuk Pingo (at the left) from the Beaufort Sea. Note the slope-side cracks that radiate from the summit cavities. They too are markers of mound degradation. Image, courtesy of R. Soare.

Image 1 Plan view of a thermokarst lake/closed-system pingo assemblage that lies 6 km sw of Tuktoyaktuk on the coast of the Beaufort Sea in northern Canada (690,26’,34” N, 1330,01’,52” W). Ibyuk Pingo, at the right, is ~48 m high; Split Pingo, at the centre, is ~38 m high. Both pingos display irregular cavities at their summits. These are markers of mound degradation. Image A27917- 35-1993, courtesy of the National Air Photo Library, Ottawa, all rights reserved. Arrow indicates approximate viewing direction of part b. b. Ground view of Split Pingo (at the right) and Ibyuk Pingo (at the left) from the Beaufort Sea. Note the slope-side cracks that radiate from the summit cavities. They too are markers of mound degradation. Image, courtesy of R. Soare.

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Dry ice gone wild: araneiform on Mars

Post by Dr. Candice Hansen and  Dr. Mary Bourke,

Planetary Science Institute, Tucson, Arizona, 85705

Geography, Trinity College, Dublin, Ireland

Every year, Mars’ polar regions are covered by a seasonal layer of CO2 ice (dry ice).  We are just beginning to understand the important role this volatile plays as an active agent of geomorphic change on Mars. The HiRISE camera on the Mars Reconnaissance Orbiter has been used to study sublimation activity in the spring for 3 Mars years.  C hannel features often organised in radial patterns were noted and known informally as “spiders”, more formally as “araneiform terrain” (Image 1).  They are tens to hundreds of m wide, with individual channels measuring several meters wide. Estimates of depth are in the order of ~ 2 m, decreasing with distance from the center of the araneform. Thin channels widen and deepen as they converge. Where they drape pre-existing topography, the channels are larger in the uphill direction suggesting they were eroded by pressurised fluid (Hansen et al, 2010).

Image 1: Subset of HiRISE Image   ESP_011420_0930 locatedf at  87.0°S / 127.27°E.  A variety of patterns of channels have been carved in the surface and are conformally-coated with seasonal ice.  At the time this image was taken, L s = 184.3 (southern spring), the sun had just started peeking above the horizon and the scene is covered with the seasonal ice cap, ~1m thick.  Araneiform channels in this image are 1-2 m deep and ~3-5 m wide.  The image is 1 km across.

Image 1: Subset of HiRISE Image ESP_011420_0930 locatedf at 87.0°S / 127.27°E. A variety of patterns of channels have been carved in the surface and are conformally-coated with seasonal ice. At the time this image was taken, L s = 184.3 (southern spring), the sun had just started peeking above the horizon and the scene is covered with the seasonal ice cap, ~1m thick. Araneiform channels in this image are 1-2 m deep and ~3-5 m wide. The image is 1 km across.

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Climbing and Falling Sand Dunes in Valles Marineris, Mars

Post by Matt Chojnacki, Devon Burr and Jeff Moersch, Earth and Planetary Sciences Department and Planetary Geosciences Institute, University of Tennessee Knoxville, USA

Aeolian transport of sand-sized particles on planetary surfaces is both enhanced and inhibited by the presence of topography.  Mountainous topography at all length scales significantly affects dune location, size, shape, and orientation [Pye and Tsoar, 1990].   The surface of Mars has both abundant sand dune populations and substantial topographic relief.  Perhaps the best example of the relationship between topography and relief is the ancient rift valleys of Valles Marineris, with over ~21,000 km2 of dune fields found within the ~10 km deep rift system [Chojnacki and Moersch, 2009].  This system of interconnected-chasms, provides natural sinks where wind blown sediment can accumulate.  Additionally, the substantial relief and the resulting atmospheric pressure gradient significantly influence the regional meteorology [Rafkin and Michaels, 2003].

Dune fields in Valles Marineris can be broadly divided into two classes: floor- and wall-related dune fields.  The “wall dunes” class dune fields are interpreted as climbing and falling dunes [Chojnacki et al., 2010].  On Earth, climbing dunes are formed when migrating dunes encounter and ascend a substantial slope or cliff (>10°), where there is no major wind flow blockage [Pye and Tsoar, 1990].  Falling dunes, found on the downwind side of large topographic highs, are formed by unidirectional down slope winds and gravity [Greeley and Iversen, 1985].

Climbing Dunes of Valles Marineris:

Image 1

Image 1: Oblique southward perspective views of Melas Chasma climbing dunes using a CTX Camera image (P16_007245_1648) over HRSC elevation (H0334). The white arrows indicate slip faces and are consistent with upslope transport. Vertical exaggeration is 2x.

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Water tracks on Earth and Mars

Post by Joe Levy, Department of Geological Sciences, University of Texas, Austin, Texas, USA

  Water tracks are zones of enhanced soil moisture that route shallow groundwater downslope in permafrost regions. Water tracks form in the active layer (the seasonally thawed portion of the permafrost) where melt water derived from snow-melt, ground ice melt, and exotic processes like salt deliquescence, concentrates in broad depressions in the ice table (the part of the permafrost that remains frozen) and flows downhill. Water tracks darken and lengthen during the summer melt season, and freeze-dry in winter, rendering them nearly undetectable from late fall to early spring.

Image 1. Quickbird satellite image of a water track in the vicinity of Lake Hoare, McMurdo Dry Valleys, Antarctica. Near-surface groundwater flows downhill from the top of the image towards the ice-covered pond at the bottom. Portion of Quickbird image orthowv02_10dec222046120-p1bs-103001000825e900_u08ns4326.

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Surface Monitoring of the “Greeley Dune Field” in Endeavour Crater, Meridiani Planum, Mars.

Post by Dr Matthew Chojnacki

Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN

The 2011 arrival of the Mars Exploration Rover Opportunity at the western rim of Endeavour crater (Cape York) provided an excellent opportunity to look for aeolian dune activity over a multi-season time span (Figs. 1 & 2) and compare them to the decade-long orbital observations documented at that site (Chojnacki et al., 2011). Here are some of the first images from a dedicated Pancam campaign to monitor these dunes and to document any aeolian surface changes (also see Chojnacki et al., 2012).

Image 1

Image 1. HiRISE (McEwen et al. 2007) image PSP_005779_1775 of Endeavour crater’s western dune field. Inset shows a CTX (Malin et al. 2007) mosaic with the dune field’s location relative to Cape York and the Opportunity rover.

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Glass-rich sand dunes and plains suggest Ice-magma interactions on Mars

Post by Briony Horgan,

Postdoctoral Fellow, School of Earth and Space Exploration, Arizona State University, USA

Several large, overlapping basins dominate the northern hemisphere of Mars, and are collectively termed the northern lowlands. This ancient basin has been infilled by sediments and hosts some of the darkest terrains on the planet. A new spectral investigation of these dark terrains has revealed that they are almost entirely composed of iron-bearing glass. This is the first detection of glass on Mars, as most other martian surfaces exhibit a typical basaltic composition with abundant olivine and pyroxene. In total, glass-rich materials cover nearly ten million square kilometers in the northern lowlands (Horgan and Bell, 2012).

Image 1

Image 1 Caption: The prime meridian of Mars from Hubble. The large dark region in the northern hemisphere (Acidalia Planitia) is approximately 5 million square kilometers in area. The north polar cap and encircling north polar sand sea can also be seen at the top of the image (NASA/Lee/Bell/Wolff)

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The effect of gravity on granular flows

Post by Dr. Maarten G. Kleinhans River and delta morphodynamics research group, University of Utrecht, The Netherlands.

 

Image 1

Image 1: Subscene of HRSC image presented in Kleinhans et al. (2010) showing an oblique view on a classic bed load-dominated Gilbert delta with a subaqueous lee slope at an angle of about 30°. Delta is about 5 km wide.

Granular materials avalanche when a static angle of repose is exceeded and freeze at a dynamic angle of repose. Such avalanches occur subaerially on steep hillslopes (Image 2), aeolian dunes and subaqueously at the lee side of deltas (Image 1). The angle varies from 25° for smooth spherical particles to 45° for rough angular particles. Noncohesive granular materials are found in many contexts, from kitchen to industry and nature. The angle of repose is an empirical friction parameter that is essential in models of numerous phenomena involving granular material, most of them actually occur at slopes much lower than the angle of repose. The angle of repose is therefore relevant for many geomorphological phenomena. (more…)

Moraines Left by Carbon Dioxide Glaciers on Mars

Post by Dr. Mikhail Kreslavsky1 and Prof. James Head2

1Assistant Research Planetary Scientist, UC Santa Cruz, USA. 2Planetary geosciences group, Brown University, Providence, Rhode Island, USA.

On Earth, cold-based glaciers (glaciers deforming internally, without basal melting and basal sliding) are found in the coldest environments (e.g., Antarctica, Marchant et al., 1993). Unlike the majority of glaciers, cold-based glaciers do not scour their substrate and leave pre-glacier topography unaffected. When cold-based glaciers advance and then dynamically stabilize (the ice flow is balanced by frontal ice ablation); debris carried forward by the glacier drops out at the glacial fronts as sublimation of the ice occurs; the dropped material produces so-called drop moraines.

In three locations at high northern latitudes of Mars, overlapping small ridges of arcuate planforms associated with slopes were interpreted as drop moraines left by extinct cold-based glaciers (Garvin et al., 2006; Kreslavsky and Head, 2011). Image 1 shows one of these locations, where a presumable glacier was formed at south-eastern part of an impact crater rim. The shapes of the extinct glacial lobes around the central peak of the crater suggest a few hundred meters thickness of the glacier.

Image 1

Image 1: Unnamed impact crater in the Northern Lowlands on Mars at 70.3oN, 266.5oE with loop-shaped ridges interpreted as drop moraines created by carbon dioxide glaciers. Image captured by Context Camera onboard Mars Reconnaissance Orbiter, image number T01_000876_2505 Illumination is from lower left.

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Weathering profiles on Earth and Mars

Post by Anne Gaudin, University Nantes, CNRS, Laboratoire LPGN, France

On Earth, weathering profiles that have developed in ultramafic rocks under tropical climate show a mineralogical transition between a Fe, Mg-rich smectite zone and an Al-rich kaolinite-bearing zone (e.g. Colin et al., 1990; Gaudin et al., 2005; Yongue-Fouateu et al., 2009). This evolution is due to an intense leaching of Mg2+ cations during the weathering process. The Murrin Murrin (MM) site is an example of such a profile located in the Archean Eastern Yilgarn Craton, in Western Australia. The MM profile is developed in serpentinized peridotite massifs over a 40 m thick sequence (Image 1) and shows three zones: serpentinized peridotites at the bottom, immediately overlain by Fe/Mg-bearing smectites and then Al-bearing phyllosilicates (kaolinite) mixed with iron hydroxides.

Image 1

Image 1: Weathering profile at the Murrin Murrin site which is currently mined for nickel, located in Western Australia (121º53’41’’E, 28º44’51’’S) (Gaudin et al., 2011).

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The periglacial landscape of Utopia Planitia, Mars

Post by Antoine Séjourné, Univ. Paris-Sud XI, CNRS, Laboratoire IDES, France

On Earth, periglacial regions underlined by continuous and ice-rich permafrost are found in areas of Northern Canada and Siberia These areas are very sensitive to abrupt climate-changes (Murton, 2001). The ice-rich permafrost has a unique assemblage of landforms, some of which are signatures of climate change (Image 1).

On Earth one example are the thermokarst lakes that have resulted from extensive thawing of permafrost following global warming during the Holocene (Czudek and Demek, 1970).  Freeze-thaw cycles of the permafrost produce ice-wedge polygons (Washburn, 1973). Localized melting of ice-wedges at the junction of the polygons induces the formation of small ponds of surface water (Washburn, 1973).

Image 1

Image 1: Assemblage of periglacial landforms in Canada (aerial photo 2009 A. Séjourné)

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Inflated Lava Flows on Earth and Mars

Post by Dr. W. Brent Garry1, Dr. Jacob E. Bleacher2, Dr. James R. Zimbelman3, and Dr. Larry S. Crumpler4

  1. Planetary Science Institute, Tucson, AZ, 85719, USA
  2. Planetary Geodynamics Laboratory, Code 698, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
  3. Center for Earth and Planetary Studies, Smithsonian Institution, National Air and Space Museum, Washington, DC, 20013, USA
  4. New Mexico Museum of Natural History and Science, Albuquerque, NM, 87104, USA

In volcanology, we are traditionally taught about basaltic lava flows advancing as toes of pāhoehoe or as channeled ‘a‘ā flows.  However, under the right emplacement conditions, some basaltic sheet flows will inflate (thicken) from only a few centimeters or meters to almost 20 meters in height.  This process occurs when lateral advancement of the flow is inhibited and liquid lava is injected underneath the solid crust of stalled sections of the flow field, causing the crust to uplift over an expanding liquid core.  The study of inflated lava flows on Earth reveals distinctive morphologic features related to this process including tumuli, inflated sheet lobes (Image 1), squeeze ups, and inflation-rise pits [1,2].  The McCartys lava flow (Image 2) is a 48-km-long, basaltic lava flow in El Malpais National Monument, near Grants, New Mexico that exhibits many of the complex morphologic features related to the process of lava flow inflation.  By studying the morphologic features that are characteristic of inflated lava flows on Earth, we can begin to identify this style of lava flow on other planetary bodies, including the Moon and Mars [3,4,5].

Image 1

Image 1. Geologist Dr. Jake Bleacher stands on the edge of a 12 meter high inflated sheet lobe in the McCartys lava flow, New Mexico. This inflated lobe continues in the foreground and extends in the distance along the left side of the photograph. Cracks, up to 8 meters deep, have formed along the margin of the lobe as the brittle crust had to accommodate for the inflation. The lower elevation unit seen in the central part of this photograph is formed from breakouts along the margin of this inflated sheet lobe and has a hummocky and swale surface texture. Photograph by W. Brent Garry. Full Size Image.

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