Astronomy Picture of the Day
January 22, 2013

Southern Spring
Southern Spring

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

In the EDM of today's APOD, countless bright, zig-zagging and whitish lanes of Carbon Dioxide (CO2) Frost (or, simply, Dry Ice) highlight an extremely intricated Network of Channels carved into the Surface of the South Polar Region of Mars. These Channels, however, are eroded a little bit more at every Martian Spring, when the Seasonal Polar Ice Cap, which at the South Pole of Mars is mostly composed of Dry Ice, sublimates (meaning that it goes directly from a solid state to a gaseus state) at the Ice-Surface Interface. The erosion occurs under the seasonal Ice Layer and, when a trapped (and pressurized) Gas Pocket finds an escape route, then it carries along some loose Surface Material. Once the Gas makes it to the open and gets dispersed, the loose Surface Material is then blown away in a downwind direction and, finally, falls down in Dark Fans on top of the Seasonal Ice Layer (see the CTX Frame and the EDM).
The Gas Pockets that are trapped in the Sub-Surface, always try to find the weakest and easiest escape-route to an open envirnoment and, in this specific area of the South Polar Region of the Red Planet, they exploited the already existing Cracks located in the Polygonal Structure of the Surface itself. As a matter of fact, Polygonal Terrain is very common at High Latitudes (even on our Home Planet Earth), and it is caused by the Thermal Contraction and Expansion of the Water Ice that is caught in the Dirt which covers the Surface.

Mars Local Time: 17:27 (Middle Afternoon)
Coord. (centered): 85,039° South Lat. and 259,056° East Long.
Spacecraft altitude: 248,8 Km (such as about 155,5 miles)
Original image scale range: 49,8 cm/pixel (with 2 x 2 binning) so objects ~ 1 mt and 49 cm across are resolved
Map projected scale: 50 cm/pixel
Emission Angle: 5,5°
Sun-Mars-MRO Spacecraft (or "Phase") Angle: 82,8°
Solar Incidence Angle: 78° (meaning that the Sun was about 12° above the Local Horizon at the time the picture was taken)
Solar Longitude: 206,9° (Northern Fall - Southern Spring)
Credits: NASA/JPL/University of Arizona
Additional process. and coloring: Lunar Explorer Italia

These pictures (which are a NASA - Original Mars Reconnaissance Orbiter CTX b/w frame identified by the serial n. ESP_029545_0950-RED_NOMAP_browse and a NASA - Original Mars Reconnaissance Orbiter EDM false-color frame identified by the serial n. ESP_029545_0950) have been additionally processed and then colorized (and re-colorized, respectively) 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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