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Martian Sky and Color of Sky Directly Overhead

Leslie Charles

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I'm interested in the opinions of Mars researchers concerning following:


If there is little dust in the Mars atmosphere, the near-horizon martian (northern hemisphere) sky during early spring seems to look jasmine (yellow with a little orange).  The color appears to change to gridelin (dark violet grey) as the distance above the horizon increases, becoming darker as the view moves toward the zenith of the martian sky.  As spring turns to summer some photographs give the impression that the jasmine color becomes less prevalent, now the jasmine to gridelin color change looks like it occurs much nearer the horizon. 


During the autumn season (northern hemisphere) the situation seems to reverse. Now, jasmine is the main color, and an observer would have to look much higher above the horizon to see where the sky changes to a gridelin color.


When there is a lot of dust in the atmosphere. The jasmine color appears to be replaced (in the instances described above"”although this would be most common in northern hemisphere winter and spring) with a salmon color (pink with much orange).  Darker salmon colors would probably imply more dust in martian atmosphere.


Any comments about the previous will be very helpful, but there is something else I am very interested in: What would a person see around noon if she were standing on the martian equator looking upward toward the sun?  In this respect would the high martian sky look something like the sky of the Earth's Moon but, perhaps, dark gridelin instead of black (with more diffusion of rays visible around the sun), and would this be the case for any season on Mars?  I found several pictures from Curiosity that looked like they were of the sun in the high martian atmosphere, but I couldn't find any description of the pictures, and I don't think any of the photos had been "rendered" to "natural" color.  See following links as examples:






The second image seems to indicate that stars are visible in the high martian sky during daylight (perhaps I should say "sol-light") hours"”is this the case?


Leslie Charles

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Hi Leslie -


  You are correct that not all of the images are color corrected. The image's "product ID " can be used to determine whether the image is in color (three bands) and what corrections have been made, if any. For example, take this Mastcam image from sol 169 http://an.rsl.wustl.edu/msl/mslbrowser/br2.aspx?tab=solsumm&p=0169MR0009100000201657E01_DRCL.


The product ID is "0169MR0009100000201657E01_DRCL". Near the end, the "E" is a product type indicator for color images. The "DRCL" indicates that the image is radiometrically corrected and is color corrected. More information is available in the Mastcam Software Interface Specification, a thorough but technically detailed description of the Mastcam data products. Access this document in the mission and instrument documents in the Resources tab. Specifically, follow this link: http://an.rsl.wustl.edu/msl/mslbrowser/tab.aspx?t=re&mi=RM, then click on Mastcam and look for MSL_MMM_EDR_RDR.DPSIS.PDF in the document listing.


Keep in mind that the browse images you see in the Analyst's Notebook are representations of the data, but not the actual science data that would be used to study seasonal atmospheric changes. These "quick look" versions are intended to give the user an idea of what is contained in a particular data product. For scientific research, one must download and work with the science data product.


The specifc data products you give are grayscale images of the sky and sun. By looking at the Mastcam data product ID, 0169ML0009080030104676C00_DRCL, you can see that this is a "C" product type, which is a grayscale image. Because it is an image of the sun, solar filters are used and they cause the non-solar part of the image to be black.


You can find more information about data products, including product IDs, in the online help at https://an.rsl.wustl.edu/msl/mslbrowser/help/default.htm#About%20the%20data/Data%20products/Data%20products.htm%3FTocPath%3DAbout%20the%20data|Data%20products|_____0

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