Astronomy Picture of the Day
August 24, 2014

Unnamed Impact Crater with Hollows
Unnamed Impact Crater with Hollows

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 High-Resolution Image (approx. 16 Km - such as about 9,936 miles - across), taken by the NASA - MESSENGER Spacecraft on October, 13, 2012, shows us a large and long Field of "Hollows" (a very common Surface Feature for the Planet Mercury) which is located within an Unnamed Northern Hemisphere's Impact Crater.

Hollows often show bright and white Halos around them, and they usually form inside, as well as on the RimsCentral Peaks, or even around (actually, in the closest proximities) of countless Mercurian Impact Craters. Here, the Hollows formed (or, maybe, are still forming) on the Crater Floor, along the base of the Crater's South-Eastern Wall, and also - but, in this second case, they are bigger in size, but smaller in number - on the very highest locations of the Crater's Complex Central Peak.

Date acquired: October, 13th, 2012
Image Mission Elapsed Time (MET): 258630853
Image ID: 2758246
InstrumentNarrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 50,63° North
Center Longitude: 320,60° East
Solar Incidence Angle (at center frame): 76,8° (meaning that the Sun, at the time that the pictures were taken, was about 13,2° above the imaged Local Mercurian Horizon)
Emission Angle (at center frame): 15,0° (meaning that the Spacecraft was a little far from being perpendicular as to the imaged Surface at the time when the picture was taken)
Sun-Mercury-Messenger (or "Phase") Angle (at center frame): 91,9°

This picture (which is an Original NASA - MESSENGER Spacecraft's b/w and Map-Projected image published on the NASA - Planetary Photojournal with the ID n. PIA 18687) has been additionally processed, contrast enhanced, Gamma corrected, magnified to aid the visibility of the details 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 outside, 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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