Between 02:21:18 UTC and 03:09:58 UTC Mastcam Left took this trio of images of the right flank of Mount Sharp.
The first thing you notice is the obvious change in the brightness of the landscape with a much more pronounced drop in the second image. My first hypothesis was that of a possible partial eclipse, but subsequent astronomical verifications have ruled out this possibility.
I would also rule out the possibility that the photos were taken with different exposure times, since not only the overall brightness varies but also the brightness ratio between the visible edge of Mount Sharp and the sky.
I would be inclined to think that this may have been a weak and temporary veiling of the Sun. In fact sometimes the Martian sky is furrowed by more or less dense clouds, although the photos of this specific Sol do not seem to show the presence of clouds.
However, the most enigmatic aspect of this sequence is the way in which the greenish areas tend to disappear as the general brightness of the landscape decreases. This detail in particular suggests to me the likely use of a polarizing filter rotated in a different position for each photo in order to study the polarimetric characteristics of the Martian soil.
Unfortunately at the moment I have not found specific information about it, but when and if will be released explanations about this unique phenomenon will be my care to publish them.
The original images are a black and white encoding of the Bayer mask that have been converted to color through a process called “debayering” or “demosaicing”. In addition, the photos have undergone a reduction in noise due to Jpeg compression, white balance and a slight increase in microcontrast and color saturation in order to make the colors more similar to what the human eye would see.
N.B. All three photos have been processed following a single scheme and setting the various filters to identical values for all photos, in order to make them perfectly comparable with each other and thus be able to appreciate the real differences in color and brightness between the photos themselves.

Original images:

28/09/2019 02:21:18 UTC https://mars.nasa.gov/msl-raw-images/msss/02539/mcam/2539ML0133610000805419C00_DXXX.jpg

28/09/2019 02:55:53 UTC https://mars.nasa.gov/msl-raw-images/msss/02539/mcam/2539ML0133620000805424C00_DXXX.jpg

28/09/2019 03:09:58 UTC https://mars.nasa.gov/msl-raw-images/msss/02539/mcam/2539ML0133630000805429C00_DXXX.jpg

This post has been automatically translated. See the original post here.

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