Astronomy Picture of the Day
March 7, 2014

The Terminator on Caloris Basin
The Terminator on Caloris Basin

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.

Small Knobs and old Impact Crater Rims can just barely catch the Sunlight when the Sun is so already low on the Mercurian Eastern Horizon. The relatively smooth Floor of the the huge Caloris Basin is on the right (Dx), while its Rim and exterior are to the left (Sx). The Knobby Texture visible outside of the Basin may be the result - according to recent speculations made by Planetary Scientists - of large Blocks of Material that were ejected by the Basin-forming Impact Event. Just to give you an idea of the dimensions of the landscape that we are looking at, consider that this frame shows an area which is approx. 492 Km (such as about 305,532 miles) across.

Date acquired: April, 27th, 2012
Image Mission Elapsed Time (MET): 244054579
Image ID: 1721895
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 40,19° North
Center Longitude: 140,50° East
Solar Incidence Angle: 88,2° (meaning that the Sun, at the time that the picture was taken, was about 1,8° above the imaged Local Mercurian Horizon)
Emission Angle: 53,7°
Sun-Mercury-Messenger (or "Phase") Angle: 142,0°

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 18063) 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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