Astronomy Picture of the Day
November 27, 2012

Features of the Mercurian Northern Hemisphere
Features of the Mercurian Northern Hemisphere

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.

Today's APOD is, once again, an Absolute Natural Color view of the Planet Mercury (this time relevant to its Northern Hemisphere), with several extremely intersting Surface Features to identify: for instance, in the North/Western portion of the frame (such as towards the upper left corner) there is part of the Crater Soseki; furthermore, a deep and long Scarp, even though it does not stand out in this high-Sun view of the Mercurian Surface, cuts through many Unnamed Impact Craters (watch the right side of the image). The bright white band crossing from the upper right to the lower left is a Ray coming from the Crater Hokusai, which is located (outside of this view and) far away to the North/East. It is interesting to notice that Hokusai's Rays overprint many older Impact Craters and, in fact, cover a large portion of the entire Planet. In order to give you an idea of the Scale of the Surface Features we just talked about, consider that the Unnamed Crater with a really bright Floor (visible towards the upper left corner of the picture) has a diameter of approx. 32 Km (such as about 20 miles).

Date acquired: April, 9th, 2011
Images Mission Elapsed Time (MET): 210807763, 210807759, 210807755
Images ID: 108194, 108193, 108192
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 36,39° North
Center Longitude: 323,5° East
Resolution: 302 meters/pixel
Solar Incidence Angle: 37,5° (meaning that the Sun, at the time that the pictures were taken, was about 52,5° above the imaged Local Mercurian Horizon)
Emission Angle: 11,2°
Sun-Mercury-Messenger (or "Phase") Angle: 48,7°

This picture (which is an Original NASA - MESSENGER Spacecraft color frame published on the NASA - Planetary Photojournal with the ID n. PIA 16356) has been additionally processed 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 - 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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