February 21, 2012
Credits: NASA/JPL-Caltech - MER Spirit - Credits for the additional process. and color.: Dr Gianluigi Barca/Lunar Explorer Italia/IPF
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Yesterday the Sunrise, today the Sunset. The only change is the Martian Region where we are looking at the Sky from: yesterday, in fact, it was the Desert of Meridiani Planum (the "Kingdom" of the NASA - Mars Exploration Rover - MER - Opportunity, still alive and well), while today is the dusty Floor of the Crater Gusev (the "Kingdom" of the NASA - Mars Exploration Rover - MER - Spirit, now officially deceased). Needless to say, the colors of the Martian Sky, before, during and right after Sunrise are VERY different as to the ones which can be seen before, during and right after (like in this picture) the Sunset. The Morning Dominant Colors, as it can be noticed easily, are a mix of Yellows and Orange shades, with large White areas, while the Evening one is just a bright Pink. The reason of this dramatic change, in our opinion, can be basically found in the amount of Dust and Water-Ice particles present in the Atmosphere at the time of Sunrise and Sunset, respectively. In other words, the colors of the Martian Sky should substantially be determined (and therefore they should be strictly related) to the so-called Atmospheric Opacity (or TAU). This means that the higher the TAU will be, the more yellow/orange colors shall be seen in the Martian Sky (which it would also appear, in the colorized pictures, kind of "thick" and "dull"); on the other hand, the lower the TAU is going to be, the more the Martian Sky will appear white and pinkish, certainly very bright, transparent and with pale blueish nuances near the Solar Disk. Of course, this is just our informed opinion, based on more than fifteen years of work, as well as on the observation of thousands of frames, taken not only by the MER Spirit and Opportunity, but also by all the Martian Landers which had the chance to take pictures of the Sky above them: from the Viking Lander One, up to the Phoenix Lander. We believe that our position is correct, but if you have a different idea, or if you wish to add anything to the above, please let us know and we shall take your notes and comments into duly consideration for the future (your credits will always be granted). This Non-linearized Sub-frame EDR was taken by Spirit's Left Panoramic Camera (PanCam) on Sol 230 of Spirit's Mission to Gusev Crater at approximately 17:37:14 Mars Local Solar Time, and the camera was commanded to use Filter 6 (482 nm). The picture has afterwards been colorized in Natural Colors (such as the colors that a perfect human eye would actually perceive if someone were on the Surface of Mars and then looked towards the Horizon, right after Sunset), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team |
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