Since 13 September 2018, the Visual Monitoring Camera (VMC) on board ESA’s Mars Express has been observing the evolution of a curious cloud formation that appears regularly in the vicinity of the 20 km-high Arsia Mons volcano, close to the planet’s equator. The cloud can be seen in this VMC image taken 10 October as the white, elongated feature extending 1500 km westward of the volcano.
A view of the region with labels is provided here.
Follow the development of this cloud via the daily images sent by the Visual Monitoring Camera on Mars Express: https://www.flickr.com/photos/esa_marswebcam/
More information: Mars Express keeps an eye on curious cloud