Astronomy Picture of the Day
November 9, 2013

Features of Tharsis Tholus
Features of Tharsis Tholus

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

Tharsis Tholus is one of the smaller so-called "Shield Volcanoes" which are located on Mars' massive "Tharsis Rise". The Main Shield is covered by a very thick Blanket (or "Mantle") of loose Dusty Material and this "Material" is, most likely, the very same Dust that is found across all of Mars. Big amounts of Dust accumulate on the tall Martian Volcanoes because the thin Atmosphere - at these elevations - has a very hard time moving away the Dust after it is dropped out from (usually) Global Dust Storms. However, another good reason for the great thickness of the Mantle of Dust here can be found in the true nature of the Dust which, as a matter of fact, could well be (mostly) "Volcanic Ash": such as a (still) Dusty Material which derived from the Volcano itself.

The Flanks of Tharsis Tholus are cut by large Channels, similar to those visible on other Martian Shield Volcanos (for instance, think about Arsia Mons and Elysium Mons) and, just like the Channels located on those huge Volcanoes, these Channels here might have probably formed by a combination of (at least) two main factors: the first one, could be a simple phenomenon of Erosion of the Surface that was caused by the action of huge amounts of fresh, flowing Lava; the second one, could just be an obvious - physical - consequence of the Collapse of the Volcano under its own weight. It is a fact, however, that a final answer about the reason of such a thick covering of Dust-like Material all over Tharsis Tholus cannot (as of today) be given with an absolute certainty.

Just out of curiosity, a very interesting circumstance (look at the Northern End of this image) is that the Dust Cover is (actually, SEEMS TO BE) much thinner on the Lava Flows that surround the Shield. This fact, once (and if) proven to be correct, would indicate that the surrounding Lavas are much younger than the Shield and that the Mantle of Dust that is found on the Volcano is older.

Mars Local Time: 14:36 (Early Afternoon)
Coord. (centered): 14,167° North Lat. and 268,433° East Long.
Spacecraft altitude: 270,8 Km (such as about 168,166 miles)
Original image scale range: 54,2 cm/pixel (with 2 x 2 binningso objects ~ 1 mt and 63 cm across are resolved
Map projected scale: 50 cm/pixel
Emission Angle: 3,5°
Phase Angle: 34,9°
Solar Incidence Angle: 38° (meaning that the Sun was about 52° above the Local Horizon at the time the picture was taken)
Solar Longitude: 26,1° (Northern Spring - Southern Fall)
Credits: NASA/JPL/University of Arizona
Additional process. and coloring: Lunar Explorer Italia

This picture (which is a NASA - Original Mars Reconnaissance Orbiter False Colors and NON-Map Projected Sub-frame identified by the serial n. ESP_033565_1945) 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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