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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It is Mercury’s fault(s)…

Post contributed by Valentina Galluzzi, INAF, Istituto di Astrofisica e Planetologia Spaziali (IAPS), Rome, Italy

Any celestial body that possesses a rigid crust, be it made of rock (e.g. terrestrial planets, asteroids) or ice (e.g. icy satellites), is subject to both endogenic and exogenic forces that cause the deformation of crustal materials. As a result of the mass movement, the brittle layers often break and slide along “planes” commonly known as faults. In particular, tensional, compressional and shear forces form normal, reverse and strike-slip faults, respectively. On Earth, plate tectonics is the main source of these stresses, being a balanced process that causes the lithospheric plates to diverge, converge and slide with respect to each other. On Mercury, there are no plates and therefore the tectonics work differently. Instead its surface is dominated by widespread lobate scarps, which are the surface expression of contractional thrust faults (i.e. reverse faults whose dip angle is less than 45°) and this small planet is in a state of global contraction.

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Image 1. Endeavour Rupes area on Mercury, image is centred at 37.5°N, 31.7°W. Top: MESSENGER MDIS High-Incidence angle basemap illuminated from the West (HIW) at 166 m/pixel. Bottom: MESSENGER global DEM v2 with a 665m grid [USGS Astrogeology Science Center] on HIW basemap, the purple to brown colour ramp represents low to high elevations, respectively. Endeavour Rupes scarp is high ~500 m. For scale, Holbein crater diameter is approximately 110 km.

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Kārūn Valles and its braided alluvial fan

Post contributed by Solmaz Adeli, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institute of Planetary Research, Berlin, Germany

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Image 1: Kārūn Valles located on the rim of the Ariadnes Colles basin. The visible channel head and deep grooves are shown (detail of CTX image D10_031182_1435). (b) The Kārūn Valles alluvial fan. Note the elongated depositional bars and their wide distribution. (c) A zoom on one of the braided bars. The flow direction is indicated by dashed arrows (detail of HiRISE image ESP_043261_1440).

The Amazonian period on Mars, meaning roughly the last 3 Ga, is globally believed to have been cold and hyperarid [e.g., Marchant and Head, 2007]. Recent geomorphological observations, however, have revealed the presence of well-preserved Amazonian-aged fluvial valleys in both the north and south mid-latitude regions of Mars [Howard and Moore, 2011; Hobley et al., 2014; Salese et al., 2016; Wilson et al., 2016]. These features point to one or several climate change phase(s) during Amazonian which could have sustained liquid water at the martian surface. These climate changes could have been triggered by obliquity oscillations [Laskar et al., 2004] causing the transportation of ice from polar regions and its re-deposition at lower latitudes. Episodic melting events during Amazonian, subsequently, formed valleys and other fluvial features, in the mid-latitude regions.

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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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An esker still physically associated with its parent glacier in Phlegra Montes, Mars

Post contributed by Colman Gallagher, University College Dublin.

Eskers are sinuous ridges composed of deposits (Image 1) laid down from meltwater flowing in tunnel-like conduits beneath glaciers (Image 2). On Earth, eskers are common components of deglaciated landscapes (Image 3) but eskers also can be observed emerging from the margins of intact glaciers.

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Image 1. A longitudinal section through part of an esker ridge in Ireland. Esker sediments are layered and often extremely coarse. The structures of the layers represent highly variable depositional settings within subglacial meltwater tunnels. The coarse sedimentary calibre represents extremely powerful meltwater flows.

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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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Pluto, Up Close!

Post contributed by Dr Veronica Bray, Lunar and Planetary Laboratory, University of Arizona.

Images of Pluto coming back from NASA’s New Horizons spacecraft have revealed many unexpected landforms and show extreme albedo and compositional variations across the dwarf planet’s surface. This blog post concentrates on one high-resolution swath across the boundary between the cratered terrains of Viking and Voyager Terra and the smoother ices of Sputnik Planum (see Figure 1). Take time to scroll down this long image (Figure 2), that covers ~530 km of Pluto’s surface at around 30°N.

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Figure 1: A global image of Pluto created from high-resolution (2.2km/pixel) panchromatic images from the LORRI instrument and lower-resolution (5km/pixel) colour data from the Ralph/Multispectral Visual Imaging Camera. The colours have been enhanced to show the diversity of the surface units by combining blue, red and near infra red images. Credits: NASA/JHUAPL/SWRI.

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A Mud Flow on Mars?

Post contributed by Prof. Lionel Wilson, Lancaster University, UK and Dr. Peter J. Mouginis-Mark, Hawaii Institute of Geophysics and Planetology, USA.

Image 1 shows a distinctive flow deposit southwest of the Cerberus Fossae on Mars.  The flow source is a ~20 m deep, ~12 x 1.5 km wide depression within a yardang field associated with the Medusae Fossae Formation.  The flow traveled for ~40 km following topographic lows to leave a deposit on average 3-4 km wide and up to 10 m thick.  The surface morphology of the deposit suggests that it was produced by the emplacement of a fluid flowing in a laminar fashion and possessing a finite yield strength. There is an ongoing debate about whether flows in this region of Mars are lava flows or water-rich debris flows.

Image 1: Location of mudflow deposit on Mars.

Image 1: Location of the distinctive flow deposit, called Zephyria Fluctus, just north of the equator on Mars. The inset at top left shows the broader context of the flow. The grey area is the flow’s extent and black boxes indicating the position of Images 2 and 3 (Fig. 2) and Image 4 (Fig. 4). The inferred flow direction is from SW to NE. Mosaic of CTX images D01_027675_1806, D04_028941_1805 and G19_025697_1803.

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A cracking comet!

Post contributed by Dr. M. Ramy El-Maarry, Institute of Physics, University of Berne, Switzerland.

The European Rosetta spacecraft went into orbit around comet 67P/Churyumov-Gerasimenko in Aug, 2014. Since then, the spacecraft’s imaging instruments, particularly the OSIRIS camera, have been sending images of the comet’s surface in unprecedented detail showing an amazingly complex landscape and a suite of geomorphological features that suggest many processes are currently at work and acting on the surface.

Image 1: OSIRIS images of various polygonal fracture systems on the surface of the comet.

Image 1: OSIRIS images of various polygonal fracture systems on the surface of the comet.

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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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Transient flow of water on Vesta suggested by gullies and lobate deposits.

Post contributed by Jennifer Scully, Dept. of Earth, Planetary & Space Sciences, University of California Los Angeles

Vesta is the second most massive asteroid in the asteroid belt, with a mean diameter of 526 km (e.g. Russell et al., 2012). High resolution images from the Dawn Mission have detected curvilinear and linera gully forms and lobate deposits in craters and on steep slopes on its surface (Scully et al., 2015).

Image 1: (a) Fonteia crater, which contains linear gullies. (b) Unmapped version and (c) mapped version of linear gullies. White arrows highlight an example linear gully in (b).

Image 1: (a) Fonteia crater, which contains linear gullies. (b) Unmapped version and (c) mapped version of linear gullies. White arrows highlight an example linear gully in (b).

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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).

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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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Is the Xanadu region on Titan an impact basin?

Post by Dr. Mirjam Langhans, GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Germany.

The surface of Titan, Saturn’s largest moon, is subject of great geologic interest, particularly since the arrival of Cassini/Huygens mission in the Saturnian System. Titan’s largest distinct and highly reflective surface feature, named Xanadu, is located close to the equator. The image depicts Xanadu in full extension with a rich diversity of geologic landforms, such as fluvial valleys, mountain ridges and impact craters. Despite the high volume of image data in this region, the geologic history behind Xanadu remains enigmatic to this day.

Geomorphologic map of Xanadu. Data: Cassini SAR data, source: (http://pds-imaging.jpl.nasa.gov/portal/cassini_mission.html). background: Cassini-ISS, source: (http://pds-imaging.jpl.nasa.gov/portal/cassini_mission.html). Inner and outer boundary of the Xanadu Circular Feature (XCF) are highlighted at Western Xanadu (black lines, according to Brown et al. (2011)). Green dots: impact craters listed in Wood et al. (2010) and Neish & Lorenz (2012), red dots: potential impact craters. Fluvial channels are delineated in blue. Dark green: lineations seen in mountain ranges, from Radebaugh et al. (2011). Light green: lineations in mountain ranges (Langhans et al. 2013).

Geomorphologic map of Xanadu. Data: Cassini SAR data, source: (http://pds-imaging.jpl.nasa.gov/portal/cassini_mission.html). background: Cassini-ISS, source: (http://pds-imaging.jpl.nasa.gov/portal/cassini_mission.html). Inner and outer boundary of the Xanadu Circular Feature (XCF) are highlighted at Western Xanadu (black lines, according to Brown et al. (2011)). Green dots: impact craters listed in Wood et al. (2010) and Neish & Lorenz (2012), red dots: potential impact craters. Fluvial channels are delineated in blue. Dark green: lineations seen in mountain ranges, from Radebaugh et al. (2011). Light green: lineations in mountain ranges (Langhans et al. 2013).

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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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Gullies on the Moon formed by dry-granular flows

Posted by Dr P. Senthil Kumar, National Geophysical Research Institute, Council of Scientific & Industrial Research, Hyderabad 500007, India.

Gullies are well-known geomorphic features on Earth where they are mainly formed by erosion due to flow of liquid water. They are also detected on Mars and the Moon and their origin on those bodies are under discussion (Malin and Edgett, 2000; Senthil Kumar et al., 2010). The gullies consist of alcoves (erosional features), channels (features indicating transportation) and fans or debris aprons (depositional structures). These features are clearly observed on the interior walls of impact craters on Mars and widely on the mountain slopes of Earth. Hence, geomorphologists use these features to examine the characteristics of liquid water flow either in the present or past geological records.

Image 1: (a) The Chandrayaan-1 terrain mapping camera image showing the ~7.2-km-diameter fresh crater (centred at 72º12'S, 133º12'E) emplaced in the peak-ring material of Schrödinger basin. The topographic profiles along A-A' and B-B' are shown in Figure 1d. A 6860-m-diameter circle fits perfectly to the crater rim from the western to the northern sides of the crater, while the crater rim recedes in other parts due to enhanced crater wall erosion. (b) The shadow-enhanced TMC image reveals the presence of arcuate ridge and the pond material on the crater floor. Note the pond is oriented toward the prominent landslide surface. (c) The TMC image showing the presence of concentric faults along the northwestern crater rim. (d) The topographic profiles along A-A' and B-B'. The interior wall that contains the landslides (B-B') is gentler and shallower than the interior wall with the gullies (A-A'). The ridge material is characterized by a higher topographic relief than the surrounding crater floor. The pond material has a flat surface that embays the ridge and other floor materials. See Senthil Kumar et al. (2013) for more details.

Image 1: (a) The Chandrayaan-1 terrain mapping camera image showing the ~7.2-km-diameter fresh crater (centred at 72º12’S, 133º12’E) emplaced in the peak-ring material of Schrödinger basin. The topographic profiles along A-A’ and B-B’ are shown in Figure 1d. A 6860-m-diameter circle fits perfectly to the crater rim from the western to the northern sides of the crater, while the crater rim recedes in other parts due to enhanced crater wall erosion. (b) The shadow-enhanced TMC image reveals the presence of arcuate ridge and the pond material on the crater floor. Note the pond is oriented toward the prominent landslide surface. (c) The TMC image showing the presence of concentric faults along the northwestern crater rim. (d) The topographic profiles along A-A’ and B-B’. The interior wall that contains the landslides (B-B’) is gentler and shallower than the interior wall with the gullies (A-A’). The ridge material is characterized by a higher topographic relief than the surrounding crater floor. The pond material has a flat surface that embays the ridge and other floor materials. See Senthil Kumar et al. (2013) for more details.

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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. Read the full post »

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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Unexpected variety among small inner satellites of Saturn

Post by Peter Thomas, Cornell University, Ithaca, New York

 Small satellites (< 150 km mean radius) usually resemble potatoes. Their irregular shapes are formed by a history of impact cratering without the benefit of internally-driven processes of volcanism, tectonics, or atmospheric effects (Castillo-Rogez et al., 2012).  During its 9 years orbiting Saturn, the Cassini spacecraft has shown that the small satellites orbiting close to Saturn have a variety of shapes, most of which deviate from the expected familiar battered potato appearance.  These objects are likely dominated by water ice as determined from mean densities and spectroscopy (Thomas et al., 2010; Buratti et al. 2010).  Satellites within rings have equatorial ridges (Charnoz et al. 2007; Porco et al., 2007).  Others, such as Janus and Epimetheus, the “co-orbitals” are almost lunar-like in appearance, close to the expected potato variety.

Image 1: Best available view of Helene. N1687119756, UV3 filter, phase = 97°, sub-spacecraft point is 2.7°N, 124.8°W.  North is down in this presentation.  Taken June 18, 2011.

Image 1: Best available view of Helene. N1687119756, UV3 filter, phase = 97°, sub-spacecraft point is 2.7°N, 124.8°W. North is down in this presentation. Taken June 18, 2011.

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Cryo-volcanic “Mount Doom” on Titan

Post by Rosaly LopesRandy Kirk,  and Mary Bourke,

Jet Propulsion Laboratory, California Institute of Technology, California, USA.
US Geological Survey, Astrogeology Science Center, Flagstaff, Arizona, USA.
Geography, Trinity College, Dublin, Ireland.

Data from the Cassini mission have revealed that Titan is a planetary body where the interior, the surface, and atmospheric processes interact to create and modify landforms (Loppes et al, 2010). In terms of recent surface processes, Titan is one of the most earth-like bodies in our solar system. Landforms include the largest area of aeolian dunefields in our solar system (e.g., Radebaugh et al., 2008), lakes (e.g., Stofan et al., 2006), fluvial channels (e.g., Langhans et al., 2012), mountains (e.g., Radebaugh et al., 2007), and features that have been interpreted as volcanic (e.g., Lopes et al., 2007).

Image 1: The  RADAR (SAR) images in black and white over a false-color mosaic of VIMS data.  The globe at upper left shows the location of the map on Titan (arrow). The white lines show the approximate boundaries of the perspective view in Image 2.

Image 1: The RADAR (SAR) images in black and white over a false-color mosaic of VIMS data. The globe at upper left shows the location of the map on Titan (arrow). The white lines show the approximate boundaries of the perspective view in Image 2.

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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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Young volcanism on Mercury

Post by Carolyn Ernst, Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA.

Prior to 2008, less than half of Mercury’s surface had been imaged at close range, during the flybys of Mariner 10 in the mid-1970s. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft completed three flybys of the planet in 2008 and 2009 on its way to insertion into orbit about Mercury on 18 March 2010 and viewed most of the planet’s surface that had never before been seen by a spacecraft. These MESSENGER images have helped to confirm some Mariner-10-based hypotheses and have elicited new science questions to be investigated.

September

Image 1: Narrow-angle camera mosaic of Rachmaninoff basin, 290 km in diameter, as seen during MESSENGER’s third Mercury flyby on 29 September 2009. Orthographic projection, ~ 440 m/pixel, centered at ~28ºN, 58ºE. MESSENGER images 0162744128 and 0162744150, credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

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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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Mercury’s Mighty Valles

Post by Dr. Paul K. Byrne, Carnegie Institution of Washington, USA

 Channel-like landforms termed “valles” (sing. “vallis”) have been observed on the Moon, Mars, and Venus, and recent results from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission show that the innermost planet hosts its own brand of valles, too. Resembling the broad outflow channels on Mars and Venus, five shallow, linear depressions form a channelized network at high latitudes in Mercury’s northern hemisphere. These valles are situated adjacent to expansive northern volcanic plains that cover some 6% of the planet’s surface, and likely conducted voluminous, low-viscosity lavas from these plains southward.

Image 1: This vallis has the steep sides, smooth floors, and erosional residuals characteristic of Mercury’s broad valles, and likely channeled lavas from left to right across the image. The image has a field of view of ca. 150 km. The 57°N parallel and 115°E meridian are shown, and Kofi basin is labeled. The image is a portion of MESSENGER’s Mercury Dual Imaging System (MDIS) global monochrome basemap, which has a resolution of 250 meters per pixel.

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Geomorphic activity on asteroid Vesta

Post by Prof. Dr. Ralf Jaumann and Dr. Mary C. Bourke,

German Aerospace Center, Berlin, Germany. 

Department of Geography, Trinity College Dublin, Ireland.

The NASA Dawn spacecraft was launched in September 2007 to characterize the conditions and processes of the solar system’s earliest epoch by investigating in detail two of the largest protoplanets remaining intact since their formation. Ceres and Vesta reside in the extensive zone between Mars and Jupiter together with many other smaller bodies, called the asteroid belt. Each has followed a very different evolutionary path constrained by the diversity of processes that operated during the first few million years of solar system evolution. The Dawn mission entered orbit around Vesta on 16 July 2011 for a one-year exploration and left orbit on 5 September 2012 heading towards Ceres.

Image A. A composite digital terrain model, and high resolution albedo mosaic and imbedded color channels of three cratres on the surface of Vesta. The image is composed of many individual photographs taken between October and December 2011 by Dawn’s framing camera during the high-altitude mapping orbit, at about 680 kilometers above Vesta’s surface. The image is centered on ~ 13° north latitude and ~ 195° eastern longitude. South is to the top of the image. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

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Sturzstroms on Saturn’s Moon Iapetus.

Post by Kelsi Singer. Ph.D Candidate, Earth and Planetary Sciences, Washington University, USA.

A typical landslide runs out less than two times its drop height whereas a long-runout landslide can extend 20-30 times the height it dropped from. Long-runout landslides (sturzstroms) are found across the Solar System.  They have been observed primarily on Earth (Image 1) and Mars, but also on Venus, and Jupiter’s moons Io and Callisto.

Image 1: An example of a long-runout landslide on Earth is the Blackhawk landslide in the Lucerne Valley, California. This landslide travelled ~8 km. Image Source USGS

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Lava temperatures determine flow composition on Earth and Io.

Post by Robert Wright, and Mary C. Bourke,

Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, US.

Department of Geography, Trinity College, Dublin, Ireland.

Image 1: A Giant plume from Io’s Tvashtar volcano composed of a sequence of five images taken by NASA’s New Horizons probe on March 1st 2007, over the course of eight minutes from 23:50 UT. The plume is 330 km high, though only its uppermost half is visible in this image, as its source lies over the moon’s limb on its far side. Image source from NASA.

The temperature at which active lava is erupted correlates well with the composition of the lava.  Mafic lavas may be up to 200-330 degrees celsius hotter than felsic lavas. The range of temperatures observed on active lava surfaces can also be used to determine the style with which the lava is erupted (i.e. as aa or pahoehoe lava flows, as lava lakes, or as lava domes). This is possible because the ease with which the crust is fractured depends on the volumetric flux of lava and its rheology (Image 2). As a result, lava bodies that fracture their cool crusts more easily (like aa flows) have hotter temperature distributions than those that fracture their upper surfaces less readily (such as viscous lava domes). Read the full post »

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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Surface dissolution on Titan and Earth: Ontario Lacus and the Etosha Pan (Namibia) .

Post by Thomas Cornet, Olivier Bourgeois, Stephane Le Mouelic et al.,

Laboratoire de Planétologie et Géodynamique de Nantes, , Université de Nantes, UMR 6112, CNRS, Nantes, France.

Titan, Saturn’s major moon, possesses hydrocarbon lakes and seas in the polar regions [Stofan et al., 2007, Hayes et al., 2008]. Among these, Ontario Lacus (72°S, 180°E, Image 1) is the largest in the south (235 km-long, 75 km-wide). So far it is interpreted as a liquid-covered lake in Titan’s southern hemisphere because of its dark appearance in Cassini image data [Barnes et al., 2009; Turtle et al., 2009; Hayes et al., 2010; Wall et al. 2010], the identification of liquid ethane in its interior [Brown et al., 2008] and the smoothness of its surface [Wye et al., 2009].

Image 1

Image 1: Ontario Lacus (Titan) and the Etosha Pan (Namibia) as surface dissolution morphologies under arid climates. Credits: Envisat ASAR, data provided by the European Space Agency ©ESA 2009, ESA ®; Cassini RADAR, data provided by JPL/NASA. Link to high resolution image

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