Astronomy Picture of the Day
March 20, 2013

Inverted Channels in Kasimov Crater
Inverted Channels in Kasimov Crater

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

By slightly enhancing an Absolute Natural Color image such as the EDM (see the inset to the right of the CTX Frame, which represents an about 1-Km wide - such as 0,621 miles - section of the whole area photographed by the NASA - Mars Reconnaissance Orbiter), can help us to achieve a better understanding of the imaged Surface Features, as well as to clearly distinguish between Surface Materials possessing different Histories, Textures and Mineral (---> Chemical) Compositions.

The whole image shows us a portion of the Floor of the Martian Impact Crater named "Kasimov" (a large - approx. 91 Km in diameter - and extremely ancient Impact Crater located in the Southern Hemisphere of the Red Planet), with several brown-gray (with subtle reddish nuances) Ridges that run from the bottom center to the upper left side of the frame. If you look carefully at all these different Ridges, you will notice that the Main Ridge is joined by a smaller one (look at the central portion of the CTX Frame) like small Tributary Rivers join together with larger ones on Earth. Indeed, this is exactly what happened here, on Mars, but - most likely - a few billions of years ago.

These Ridges are called "Inverted Channels" and they mark the locations of ancient Martian Riverbeds (in this case the Main River flowed towards the upper left of the image). Such Inverted Channels formed because the bottoms of these Rivers (---> Tributaries) were all full of Gravel-sized Rocks, whereas the areas around them were made of fine Clays. A VERY long time after the Rivers stopped flowing and dried-up, the Wind, slowly, removed completely the fine and light Clays, but it was not strong enough to blow away the heavy Gravel. In the end, after all the Clays were gone, the old Riverbeds were left as High-standing Gravel Ridges, such as the ones very well visible here (both in the CTX Frame as well as in the EDM).

Mars Local Time: 15:49 (Middle Afternoon)
Coord. (centered): 35,729° North Lat. and 129,386° East Long.
Spacecraft altitude: 258,2 Km (such as about 160,3 miles)
Original image scale range: 25,8 cm/pixel (with 1 x 1 binning) so objects ~ 78 cm across are resolved
Map projected scale: 25 cm/pixel
Emission Angle: 11,0°
Sun-Mars-Spacecraft (or Phase) Angle: 47,6°
Solar Incidence Angle
: 58° (meaning that the Sun was about 32° above the Local Horizon at the time the picture was taken)
Solar Longitude: 203,7° (Northern Fall - Southern Spring)
Credits: NASA/JPL/University of Arizona
Additional process. and coloring: Lunar Explorer Italia

The CTX Frame (which is an Original Mars Reconnaissance Orbiter non-map projected b/w frame, identified by the serial n. ESP_030609_1550) and the EDM (which is an Original Mars Reconnaissance Orbiter enhanced color frame, identified by the serial n. ESP_030609_1550-1) have both been additionally processed and then colorized (as far as the EDM is concerned, 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 Kasimov Crater - 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 Kasimov Crater, each having a different Albedo (---> Reflectivity) and Chemical Composition.

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