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.

lobesOfDifferentKinds_IAG_IOTM

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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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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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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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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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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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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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…)

Unconsolidated Gravels on Asteroid Itokawa

Posted by Dr. Hirdy Miyamoto,    

(Re-posted from IAG Image of the Month, November 2007)

In November 2005, the Hayabusa spacecraft performed touchdown rehearsals, imaging navigation tests, and two touchdowns on Itokawa, which is by far the smallest asteroid ever studied at high resolution.

Asteroid Itokawa

Image courtesy ISAS/JAXA and University of Tokyo

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Landslide deposits on Mars

Posted by Bill Hartmann, Planetary Science Institute, Tucson, Arizona, USA.

(Re-posted from IAG Image of the month, March 2007)

This high-resolution MGS MOC image shows overlapping landslide deposits at the foot of the wall in the Ganges region of the Valles Marineris canyon complex on Mars. (more…)

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