Astronomy Picture of the Day
November 5, 2012


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 Unnamed Crater (with a diameter of about 14 Km) must possess some quality that makes it a good "haven" for Hollows: in fact, as you can see, Hollows cover a large region of its Floor, as already seen at Tyagaraja Crater and in very many other locations of Mercury. In this case, the Hollows are also located near the Crater's Rim, as well as on some (apparently sandy) Material that is sliding down the Crater's Walls.

As you remember, we have already written about this Mercurian Oddity, some time in the past, and we have also already underlined that a theory that is fully capable to explain the origin of the Hollows still does not exist. However, like some Researcher in our Group is speculating, since it appears (as the NASA Scientists have already suggested) really very possible that Hollows keep being created on Mercury even at present time, it is a logic and reasonable possibility that they could form as a consequence of a condition that is recurrent to the Planet Mercury. Then which one? Maybe, we think, the extreme heating that the Mercurian Surface is subject to, in particular, when the Sun shines very high in the Sky; an extreme heating that may cause pockets of gas (or other volatiles) present in the Subsurface, to quickly expand and then suddenly escape through existing gaps and cracks (or, in case there are no already available way outs, even by infiltrating through some less compacted area of the Subsurface itself and keep "pushing", until they can finally reach the open). The Hollows then, according to this hypothesis, would just be the physical and visible evidence that an Outgassing Event has occurred.

All that said, we believe, as IPF, that, one day, the NASA - MESSENGER Spacecraft might well witness to the creation of some Hollows, thus helping Scientists to better understand this unusual phenomenon and, perhaps, to explain it in a definitive and convincing way. And since the solution of this enigma is, once again and most likely, just a Matter of Time, we keep waiting and observing...

Date acquired: July, 19th, 2012
Image Mission Elapsed Time (MET): 251199474
Image ID: 2229903
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Center Latitude: 41,24° North
Center Longitude: 123,8° East
Resolution: 18 meters/pixel
Solar Incidence Angle: 67,0° (meaning that the Sun, at the time that the picture was taken, was about 23° above the imaged Local Mercurian Horizon)
Emission Angle: 41,5°
Sun-Mercury-Messenger (or "Phase") Angle: 108,6°

This picture (which is an Original NASA - MESSENGER Spacecraft b/w frame published on the NASA - Planetary Photojournal with the ID n. PIA 16397) 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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