lundi 23 janvier 2017

The Beauty of Layered Stratigraphy & The Changing Dunes of Wirtz Crater












NASA - Mars Reconnaissance Orbiter (MRO) patch.

Jan. 23, 2017


The layered bedrock in this image was brought from several kilometers of depth during the formation of this 44 kilometer wide crater in the volcanic plains of Lunae Planum.

As these layers were exhumed and brought to nearly vertical orientations, faulting and fracturing occurred and breccia dikes formed. Breccias are rocks consisting of angular and sharp fragments, and a dike is a fracture that has been widened by forces pulling apart the rock while simultaneously filling it with rocky materials. Breccia dikes are a common feature in terrestrial craters and can now be recognized in brilliant preservation on Mars.

This high-resolution, false-color image cutout above allows us to see a cross-cutting breccia dike near the bottom of the image.

This is a stereo pair with http://www.uahirise.org/ESP_017055_1975

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.

The Changing Dunes of Wirtz Crater 


The large dark feature is a classic Martian sand dune. Most sand on Earth is made from the mineral quartz, which is white and bright. On Mars, most sand is composed of dark basalt, a volcanic rock. For this reason, dunes on Mars are darker than those on Earth.

The dunes in this observation, within Wirtz Crater, are known as "barchans." The steepest slope is on the eastern (right) side, partially in shadow, and represents the direction the dune is migrating as the sand is blown and transported by the wind. Small ripples are visible on much of the dune surface. The dark streaks on the dune are tracks left by passing vortices known to us as dust devils. These raise dust off the dune, revealing a darker substrate.

This is a stereo pair with http://www.uahirise.org/ESP_021893_1315

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.

Mars Reconnaissance Orbiter (MRO): http://www.nasa.gov/mission_pages/MRO/main/index.html

Images (mentioned), Text, Credits: NASA/JPL/Tony Greicius.

Best regards, Orbiter.ch

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