Astronomy Picture of the Day
September 23, 2012

Proximities of Ma'adim Vallis
Proximities of Ma'adim Vallis

Credits: ESA/ DLR/ FU Berlin (G. Neukum) - Credits for the additional process. and color.: Dr Paolo C. Fienga/Lunar Explorer Italia/IPF

Today's APOD is an ESA - Mars Express Orbiter image-mosaic of a Region close to Ma’adim Vallis, which is one of the largest Outflow Channels of Mars, about 700 Km long and significantly larger than Earth's Grand Canyon. As a matter of fact, Ma’adim Vallis is over 20 Km wide and about 2 Km deep in some places; it originates in the Southern Lowlands (---> Plains), in a Region close to the "Dichotomy Boundary" (remember that the Dichotomy Boundary is a narrow Region separating the Cratered Highlands, located mostly in the Southern Hemisphere of Mars, from the Northern Hemisphere's Lowland Plains), and it ends in Gusev Crater, such as near the Martian Equator.

Many Scientists believe that enormous quantities of Water coming from Ma'adim Vallis may have collected in Gusev Crater, thus forming a giant Lake, and the NASA - Mars Exploration Rover (MER) Spirit was sent there, inside Gusev Crater, just to investigate that possibility (but the results of the search, as far as we know for now, as IPF, have been inconclusive). However, Ma'adim Vallis is thought to have been carved by flowing Water early in Mars' History, and some of the short narrow Channels along the Walls of Ma'adim are probably "Sapping Channels"; the "Sapping Process" occurs when a certain (and obviously significant) quantity of Groundwater, through a long, erosive action, partially dissolves the Rocks over and around it and, in time, by undermining their stability, causes them to collapse. The sign that such a Sapping Process has occurred can be found in the presence, on the Surface near the aformentioned (relatively) short and narrow Channels, of large Debris Deposits (consider, however, that sometimes even these large Deposits get - litterally - swept away and cancelled by the consuming action of other - most likely Aeolian - Erosional Processes).

The Region imaged in the pictures forming the mosaic lies to the South-East of Ma’adim Vallis and the mosaic is centered at about 29° South Latitude and 182° East Longitude, with a Ground Resolution of approx. 15 meters per pixel.

This frame (which is the Original ESA - Mars Express HRST b/w mosaic n. 440-20090629-6393-6-co-01_H1) has been additionally processed and then colorized in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the ESA - Mars Express 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. Different colors, as well as different shades of the same color, mean, among others, the existence of different Elements present on the Surface of Mars, each having a different Albedo (---> Reflectivity) and Chemical Composition.

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