thelxiepeia: Clouds on Mars, photographed by Mars Express, 23rd October 2010.
37 to 45°S, 207 to 210°E on the Terra Sirenum. The crater at bottom center is Hipparchus, 95 km across. The terrain seen here slopes up from north to south - a change in elevation of about 5,000 m - which may be what constrains the thicker clouds. There appears to be a strong wind at top left; this may be blowing downslope from highlands out-of-frame left.
Animation of 5 monochrome images, colourized with 3 visible light images. Colour balance adjusted to remove much of a very strong yellow cast to the composite image.