Astronomy Picture of the Day
April 11, 2013

Mercurian Craters' Variety
Mercurian Craters' Variety

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.

This oblique view of the Surface of Mercury highlights, from top to bottom, the Impact Craters Balzac, Phidias,Tyagaraja, Stevenson, and Zeami. While named Impact Craters are still sparse across much of the Surface of Mercury, this Region, since it had already been observed by the NASA - Mariner 10 Spacecraft, granted to Planetary Scientists and Researchers plenty of time to propose names to the International Astronomical Union (or IAU, for short) and get them approved. Furthermore, in the NASA - Mariner 10 images of Mercury, Craters like Tyagaraja (located at the center of the image and having a diameter of approx. 97 Km - such as about 60,2 miles) and Zeami were described as hosting "Bright Floor Deposits", but the relatively low resolution at which they were imaged at that time did not allow the Planetary Scientists to carry out a more detailed analysis.

Now, thanks to the imaging capabilities of the cameras onboard the NASA - MESSENGER Spacecraft, we know that the Mercurian Impact Craters such as these visible in today's APOD, actually do not host "Bright Floor Deposits" but rather that fascinating (and still far from being fully understood) Features known as "Hollows".

Date acquired: November, 26th, 2012
Images Mission Elapsed Time (MET): 262401199, 262401219, 262401203
Images ID: 3026482, 3026487, 3026483
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 4,64° North
Center Longitude: 210,50° East
Resolution: 698 meters/pixel
Solar Incidence Angle: 30,2° (meaning that the Sun, at the time that the picture was taken, was about 59,8° above the imaged Local Mercurian Horizon)
Emission Angle: 57,5°
Sun-Mercury-Messenger (or "Phase") Angle: 83,8°

This picture (which is an Original NASA - MESSENGER Spacecraft false color image-mosaic published on the NASA - Planetary Photojournal with the ID n. PIA 16907) has been additionally processed 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 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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