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. 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.
Posted by suja82 on June 19, 2015
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.
Posted by megafloods2013 on October 1, 2014
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).
Posted by megafloods2013 on April 1, 2014
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.
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.
Posted by megafloods2013 on January 1, 2014