Astronomy Picture of the Day
October 18, 2012

Eitoku Crater
Eitoku Crater

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 main and really impressive Impact Crater visible in this NASA - MESSENGER Spacecraft image, Eitoku (which has a diameter of approx. 100 Km - such as about 62 miles) , displays several (almost) Central Peaks that appear especially prominent due to the high Solar Incidence Angle (meaning that the Sun was setting onto the imaged Local Horizon at the time that this picture was taken - and therefore the shadows of each and every Mercurian relief resulted way more visible - i.e.: longer - and suggestive) as well as to the fact that this frame has not been Map Projected. Note that Central (and/or almost Central, like in this case) Peaks are a relatively common Feature in Mercury's larger Impact Craters. Note, also, that the smaller Impact Craters visible on the Floor and Rim (which, on its side, appears quite degraded) of Eitoku Crater indicate/suggest that we are actually looking at an old Impact Feature.

Date acquired: July, 3rd, 2012
Image Mission Elapsed Time (MET): 249790754
Image ID: 2129670
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 21,77° South
Center Longitude: 202,6° East
Resolution: 120 meters/pixel
Solar Incidence Angle: 83,4° (meaning that the Sun, at the time that the picture was taken, was about 6,6° above the imaged Local Mercurian Horizon)
Emission Angle: 59,9°
Sun-Mercury-Messenger (or "Phase") Angle: 134,5°

This picture (which is an Original NASA - MESSENGER Spacecraft b/w frame published on the NASA - Planetary Photojournal with the ID n. PIA 16361) has been additionally processed 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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