Astronomy Picture of the Day
November 12, 2013

Migrating Dunes on the Rim of the Hellas Impact Basin
Migrating Dunes on the Rim of the Hellas Impact Basin

Credits: NASA/JPL-Caltech/University of Arizona - Credits for the additional process. and color.: Dr Paolo C. Fienga/LXTT/IPF

Sand Dunes, such as those visible in this NASA - Mars Reconnaissance Orbiter image, have been aften observed to creep (---> move) slowly all across the Surface of Mars (through the action of the Wind). These Sand Dunes here are a particular type of Dunes - called "Barchan" - which form when the Wind (actually, a so-called "Dominant Wind") blows in one direction (here, East to West) for long periods of time.


Barchan Dunes are an extremely common Aeolian (---> Wind related) Surface Feature on Mars, as well as in the Desert Regions of our Home Planet Earth. These specific Barchan Dunes are found on the Western Rim of the huge Hellas Impact Basin, which is located in the Southern Hemisphere of the Red Planet. All the visible area is covered by extensive Deposits of Layered Rocks that, probably, were initially deposited on the Surface as loose (---> separated, free standing) Sediments and which, over a very long period of time, formed some visible Rocky Layers. In time (still a VERY long one...), some portions of these Layered Rocks were eroded away by the (relatively continuous) Winds' Action, and the remaining Layers now form a number of Flat-topped Hills known as "Mesas". The Barchan Dunes that we are looking at here, formed in the so-called "Lee" (---> Downwind Side) of the aformentioned Mesas.


This area was previously image by the HiRISE in the AD 2008 (PSP_007676_1385) and was then retargeted through a public request (http://www.uahirise.org/hiwish). Careful comparison of repeat images such as these, can reveal the speed and manner by which the Dunes move across the Martian Surface. This information, among other things, can be used to study the Current Status of the Atmosphere of Mars, the Age and Mobility of the Sand Deposits found on the Planet's Surface and, last but not least, the Hazards (---> Risks) that Sand Dunes may pose to landed vehicles, such as Rovers. Over the course of its Mission, the Science Instruments onboard the NASA - Mars Reconnaissance Orbiter (or "MRO" for short) have returned over 200 Terabits of data back to Earth. This image was taken on November 4, 2013, such as the very same day when the MRO's 200-Terabit Mark was reached and surpassed.


This picture (which is a NASA - Original Mars Reconnaissance Orbiter False Colors and NON-Map Projected Sub-frame published on the NASA - Planetary Photojournal and identified by the serial n. PIA 17675) has been additionally processed, magnified, contrast enhanced, Gamma corrected, and then re-colorized in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Mars Reconnaissance Orbiter and then looked down, towards the Surface of Mars), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team.



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