Astronomy Picture of the Day
October 17, 2013

Volcanic Vent?
Volcanic Vent?

Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington and Dr Paolo C. Fienga/LXTT/IPF for the additional process. and color.

The Mercurian Region known as Caloris Basin contains a complex mix of Impact, Tectonic, and Volcanic Surface Features and, at the center-right of this picture, the Elongate Depression which dominates the scene could be a Volcanic Vent . As a matter of fact, this specific Surface Feature highlights the ambiguity that sometimes arises in discerning whether a Surface Depression is due to an Impact (perhaps Secondary in nature) or to a Volcanic Event, considering that both occurrences can leave (as they actually do, many times) some kind of Elongate Depressions. However, one (but, in our opinion, as IPF, very questionable) clue that this Feature might point to Volcanism can be found in the circumstance that the Depression shows a slightly Irregular Shape. Furthermore, the apparent lack of a Rim of Impact Ejecta (that usually raises above the Baseline Level of the surrounding Terrain) is (better yet: could be) another circumstance (but, even in this case, really weak and basically unsubstantiated) pointing towards the Volcanic nature of the Feature.

Date acquired: June, 30th, 2013
Image Mission Elapsed Time (MET): 14936140
Image ID: 4355811
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 24,18° North
Center Longitude: 148,10° East
Solar Incidence Angle: 66,0° (meaning that the Sun, at the time that the picture was taken, was about 24,0° above the imaged Local Mercurian Horizon)
Emission Angle: 50,3°
Sun-Mercury-Messenger (or "Phase") Angle: 115,4°

This picture (which is an Original NASA - MESSENGER Spacecraft's b/w and NON-Map-Projected image published on the NASA - Planetary Photojournal with the ID n. PIA 17497) has been additionally processed, contrast enhanced, magnified and then colorized in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - MESSENGER Spacecraft and then looked down, towards the Surface of Mercury), 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 other things, the existence of different Elements (Minerals) present on the Surface of Mercury, each having a different Albedo (---> Reflectivity) and Chemical Composition.

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