Astronomy Picture of the Day
September 14, 2014

Hemingway Crater and Surroundings (Part I - CTX Frame)
Hemingway Crater and Surroundings (Part I - CTX Frame)

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 (approx. 290 Km - such as about 180,09 miles - across), made out of three frames taken by the NASA - MESSENGER Spacecraft on July, 15, 2014, we can see, in the upper central position of the picture, the Mercurian Impact Crater named Hemingway, in Absolute Natural Colors. Hemingway Crater is approx. 130 Km (such as about 80,73 miles) in diameter, with a relatively pale orange/brown Floor and a very unusually-looking patch of very dark Material (whose origin and composition are still unknown) deposited in its center.

This Impact Crater, if you pay special attention to the details, shows several irregular Depressions on its Floor, which are fairly common in other Mercurian Impact Craters and that may be due to the occurrence, in a very remote past, of Explosive Volcanic Events; however, the Low-Reflectance, Dark Patch of Material very well visible on its Floor may also point to a more complex Geologic History of this Feature (which, unfortunately, we may never be able to fully reconstruct and understand).

Just out of curiosity, and no matter how unusual it may seem, no Hollows are visible inside or even near (---> in the closest proximities) of Hemingway Crater.

Date acquired: July, 15th, 2014
Images Mission Elapsed Time (MET): 47756996, 47757016, 47757000
Images ID: 6688394, 6688399, 6688395
InstrumentWide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 16,51° North
Center Longitude: 356,90° East
Solar Incidence Angle (at center frame): 19,2° (meaning that the Sun, at the time that the pictures were taken, was about 70,8° above the imaged Local Mercurian Horizon)
Emission Angle (at center frame): 60,3° (meaning that the Spacecraft was far away from being perpendicular to the imaged Surface at the time when the pictures were taken)
Sun-Mercury-Messenger (or "Phase") Angle (at center frame): 77,9°

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 18808) 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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