There is an unknown white cloud across the sky over the Martian equator.
It is not the first time researchers have seen this so they have some hypothesis about it. Similar images were captured back in 2009, 2012 and 2015 by Mars Express.
The cloud covers 1,500 kilometers over Arsia Mons and appeared on a picture taken by Mars Express orbiter on September 13.
It appears to rise above a dead volcano but researchers from the European Space Agency believe that this is just an illusion of the eye since Mars did see any eruption along millions years. However, the high peak of Arsia Mons has remained responsible for this phenomenon called the orographic cloud.
They’re typically seen on the downwind side of mountains, forming when dense air close to the surface flows uphill and expands, cooling to a temperature that allows moisture to condense on particles of dust.
Clouds over Arsia Mons are a common sight throughout most of the year, tending to clear in the months prior to the Northern Hemisphere’s winter solstice.
After a long period of time, due to the seasonal conditions and temperature on Mars there are clouds forming from water ice. The foggy moisture air blows up from the volcano peak.
The reappearance of this cloud on 2018 allows researcher to explore more the density of the particles in the atmosphere. It can help the researchers reconstruct the models of how dust rises and settles on the planet Mars giving further information for the scope missions.