Astronomy Picture of the Day
July 21, 2014

Unnamed Crater with White and Bright Rays
Unnamed Crater with White and Bright Rays

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 an image-mosaic (approx. 566 Km - such as about 351,486 miles - across) that has been obtained by putting together three frames taken by the NASA - MESSENGER Spacecraft  on December, 10, 2013. It shows us an "explosion" of stunning Rays, all radiating from an Unnamed Impact Ccrater located near Mercury's Equator. The bright Ejecta Rays resulted from Impacts Ejected Sub-Surface Material. Because the Sub-Surface Material is relatively unweathered - as compared to the nearby Surface Terrain -, the Rays appear to be of a bright white, in this Absolute Natural Color image-mosaic.


A large amount of so-called "Low Reflectance Material" (or "LRM", for short, which is very common on Mercury and that appears of a dark-gray color - actually, almost black, in fact - here) can be seen to the West-South/West on the Crater as well as to the North (but in a much lesser quantity). Furthermore, on the other hand, to the very West (Sx) of the Crater, a Cluster of - most likely - extremely ancient Primary Impact Craters is also well visible while, to the East (Dx) of the Rayed and still Unnamed Impact Feature, a system of several sinuous Ridges (or - maybe - the highly eroded and now extremely irregularly-shaped remnants of the Outer Rim of a much larger and older Impact Crater) can easily be spotted.


Date acquired: December, 10th, 2013
Images Mission Elapsed Time (MET): 28990861, 28990857, 28990855
Images ID: 5355052, 5355050, 5355049
InstrumentWide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 0,68° South
Center Longitude: 95,97° East
Solar Incidence Angle: 32,6° (meaning that the Sun, at the time that the picture was taken, was about 57,4° above the imaged Local Mercurian Horizon)
Emission Angle: 49,5° (meaning that the NASA - MESSENGER Spacecraft was highly oblique as to the imaged Surface)
Sun-Mercury-Messenger (or "Phase") Angle: 82,1°


This picture (which is an Original NASA - MESSENGER Spacecraft's false colors and Map-Projected image-mosaic published on the NASA - Planetary Photojournal with the ID n. PIA 18532) has been additionally processed, contrast enhanced, Gamma corrected, magnified to aid the visibility of the details 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 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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