Astronomy Picture of the Day
April 23, 2014

Buried Crater near the Mercurian Terminator
Buried Crater near the Mercurian Terminator

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.

In this image-mosaic, obtained by putting together two frames taken - in rapid sequence - by the NASA - MESSENGER Spacecraft on March, 9, 2014, we can see a large (approx. 180-Km - such as about 111,78 miles - diameter) and extremely ancient Mercurian Buried Impact Crater (which occupies about the whole visible area here). This Unnamed Impact Crater was almost completely buried, eons ago, by huge Volcanic Flows that now, after they have solidified, form those Volcanic Plains which make up most of the Northern Hemisphere's Smooth Plains of Mercury.

It has been the Rim of this Buried Impact Crater - especially in its South/Eastern side - that has helped Planetary Scientists to localize the occurrence, in this area, of some so-called "Compressional Deformation" of the Ground, which led, eventually, to an unusually-looking Wrinkle-Ridge Ring. Furthermore, the entire central portion of the Crater is, as you can see, heavily criss-crossed by Extensional Graben-like Landforms. This whole scene, in our opinion, as IPF, is very suggestive not only because of the pictured unusually-looking Buried Impact Crater, but also because, being the Sun extremely low on the Local Mercurian Horizon, all the visible Reliefs appear, somehow, "deeper" and better defined (thanks, of course, to the long and sharp Shadows that are announcing the incoming nightfall).

Date acquired: March, 9th, 2014
Images Mission Elapsed Time (MET): 36713179, 36713230
Images ID: 5903920, 5903921
InstrumentWide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 64,40° North
Center Longitude: 23,80° East
Solar Incidence Angle: 86,2° (meaning that the Sun, at the time that the picture was taken, was about 3,8° above the imaged Local Mercurian Horizon)
Emission Angle: 51,1°
Sun-Mercury-Messenger (or "Phase") Angle: 137,3°

This picture (which is an Original NASA - MESSENGER Spacecraft's b/w and Map-Projected image-mosaic published on the NASA - Planetary Photojournal with the ID n. PIA 18214) 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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