Mike Mellon wrote:Stunning Landscape Near Mamers Valles (ESP_028313_2220)
This region of Mars has been long studied for its evidence of glacial-like flow features. The landscape is dominated by flat top mesas and flat valley floors. But a closer look shows evidence that soil material is flowing ever so gradually from the edges of the mesas out into the valleys.
Such flow can result from excessively ice-rich deposits analogous to glaciers. "Streamlines" (curved ridges) mark the flow direction, while "flow fronts" mark where material has reached its furthest extent or where material has collided with an obstacle or otherwise bunched up.
The close up view from HiRISE reveals even stranger textures on the valley floor. Scarps and hills appear twisted like taffy, probably the result of the slow movement of the subsurface ice. Other areas that appear flat and smooth at lower resolution are expanses of extremely regular small pits ans mounds at HiRISE resolution. One suggestion has been that these small-scale textures are the result of sublimation (evaporation) of subsurface ice combined with the taffy-like shifts in the ground surface.
HiRISE Science Team wrote:Layers in Northeast Sinus Meridiani (ESP_028353_1815)
The objective of this image is to examine the exposure of thin layers along the walls of a few-kilometer-wide valley in Sinus Meridiani.
These layers can then be compared to other observations of layers in the region, allowing scientists to map individual layers over much larger regions than covered by a single image. Understanding the regional extent of layers will aid in studies of the past environmental conditions on Mars that led to the formation of these layers.
Sinus Meridiani also has vast outcrops of sedimentary rocks with a great deal of diversity. The region covers an area about the size of the Colorado plateau in the United States.
Alfred McEwen wrote:Martian Mélange (ESP_029484_1670)
"Mélange" means a confusing mixture, and is used to describe rocks scraped off the top of a downward-moving tectonic plate in a subduction zone on Earth. On Mars it is probably mostly impact cratering that creates such chaotic mixture of rock types rather than plate tectonics.
These warm, enhanced colors are due to minerals altered by water, whereas the blue and green colors are from unaltered minerals such as olivine and pyroxene.
This image was acquired in Tyrrhena Terra, some of the most ancient highlands of Mars.
Credit: NASA/JPL/University of Arizona
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