After downlading the great work of Voekoevaka in the Neptune and Mars cloud maps, I remember a planetary mars cloud map somewhere else and finally I found it in the webpage image archive of the Mars Orbital Surveyor here named MOC2-143. After decomposing it in RGB layers, taking and editing the blue channel, I was able to made a surprisingly good cloud map based in the MOC image. Give it a try, it is less than 1 MB image.
Click on the image for full size:
-Tharsis with clouds
-Tharsis without clouds
-Syrtis Major, Elysium and Hellas with clouds
-Syrtis Major, Elysium and Hellas without clouds
Download link ------------------- Don't forget to read the instalation instructions readme file.
Very nice map! It have some issues though (like non-zero transparency in a transparent areas, what makes Mars' limb a bit darker). May I ask a source cylindrical texture (I mean before precessing by CubeMap)? I may fix it and add as a default Mars clouds in the next release.
Well I must confess that I was moving in the dark with the transparency issue, but I think I was able to fix the dark problem (I didn't selected and deleted the black pixels around the clouds . Down here you have the fixed cylindrical projection:
Thanks! Also, you must know what SE don't support grayscale + alpha textures (it can render it, but can't generate mipmaps correctly, which can cause visual artifacts). And clouds textures really doesn't need the alpha channel. Simply grayscale is enough.
From there you can just select (in GIMP) with the color tool selection as many black pixels as you want adjusting the threshold option (for example I used 8 in this new version), deleting and decreasing opacity.
My work for SE: Click here Textures for Venus surface in color and the moons of Saturn, Uranus and Neptune Catalogs of binary stars, brown dwarfs, black holes and neutron stars.