Extremely long and narrow orographic clouds on Mars

We report new cases of extremely long and narrow clouds similar to the cloud formed at Arsia Mons (AMEC) (Hernández-Bernal et al, 2021) that form at mid-temperate and subpolar latitudes in both hemispheres of the planet.

For this study, we use the images obtained by the VMC camera on board the Mars Express mission. Given Mars Express’ advantageous polar elliptical orbit, we are able to characterize these clouds at different local times (during morning hours when these clouds develop) and spatial resolutions. 

We study the properties of the orographic elongated clouds that form in three regions with different topography: The volcanic region of Alba Patera (250°E, 40°N), the rugged mountain range of Thaumasia Highlands and Lyot crater (29.3°E, 50.4°N). The elongated clouds at Alba Patera form during the northern fall and winter between  Ls = 170° - 330° and can reach lengths of up to 2600 km with widths of 250 km. Similarly, the elongated clouds at Lyot crater form during Ls = 180° - 340° and can have lengths of up to 3000 km and widths of 300 km. Lastly, the elevated region of Thaumasia Highlands forms many elongated clouds. However, the longest clouds form at 269.5°E, 39°S and can have lengths of up to 2700 km and widths of 200 km. These clouds form during the southern fall and winter during solar longitudes Ls = 0° - 60° and Ls = 110° - 165°.