Massive Cloud Forming Over One of Mars' Biggest Volcanoes Is Icy Water Vapour, Not Eruption

It's due to a routine but dramatic-looking meteorological phenomenon called orographic lifting.

from gizmodo http://www.gizmodo.co.uk/2018/10/massive-cloud-forming-over-one-of-mars-biggest-volcanoes-is-icy-water-vapour-not-eruption/