Astronomy Picture of the Day
July 2, 2013

Lights and Shadows at Hokusai (EDM)
Lights and Shadows at Hokusai (EDM)

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.

This frame (taken by the NASA - MESSENGER Spacecraft on July, 29, 2011) focuses on the Central Peaks' System and Impact Melt of Hokusai Crater (the scene here, just to give you an idea of the actual dimensions and proportions of this Mercurian Location, is approx. 28 Km - such as about 17,38 miles - across). The contrast between the illuminated - and therefore very bright (in fact, almost oversaturated) - sides of the Peaks and, on the other hand, their totally, and deeply, Dark Shadows, make this scene extremely suggestive and, in a way, also kind of romantically evocative; furthermore, it is interesting to note that the very smooth Floor surrounding the Central Peaks' System is the final result of the cooling Impact Melt (---> litterally, a "Sea of melted Rock") that was generated by the intense heat and energy which were, respectively, emanated and expressed by the Impact Event.

Just out of curiosity, the extremely "pointed" (and, in a way, very similar to a "pyramid") shadow visible in the lower left quadrant of the frame, does not mean nor imply that the Relief which is projecting it is a real "Pyramidal Structure" (like many pseudo-scientists have often said and speculated). As a matter of fact, the Peak that the pointed shadow comes from, as seen from the Surface of Mercury, is very far away from even barely looking like a pyramid! Sharp and pointed shadows are just common Visual Features characterizing airless Celestial Bodies (we can see many similar shadows even on our own Moon) and they can often be seen on Reliefs standing on or near the Terminator Line (such as in Regions where the Sun - just like in this case - is very low on the Local Horizon).

Date acquired: July, 29th, 2011
Image Mission Elapsed Time (MET): 220460258
Image ID: 566860
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 58,03° North
Center Longitude: 16,52° East
Solar Incidence Angle: 75,4° (meaning that the Sun, at the time that the picture was taken, was about 14,6° above the imaged Local Mercurian Horizon)
Emission Angle: 28,5°
Sun-Mercury-Messenger (or "Phase") Angle: 104,0°

This picture (which is a crop taken from an Original NASA - MESSENGER Spacecraft's b/w Map-Projected image published on the NASA - Planetary Photojournal with the ID n. PIA 17289) 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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