Astronomers have been watching the curious 900-mile cloud for more than a month
A BIZARRE image shows what looks like a giant plume of smoke stretching 900 miles over the surface of Mars – despite fire being impossible on the Red Planet.
Astronomers have been watching the curious cloud for more than a month through pictures beamed back from a European probe circling the planet.
It has remained in place since September 13 over Arsia Mons, a volcano near the Martian equator, the European Space Agency said.
But Arsia Mons has been extinct for around 50million years and no volcanic activity is producing the cloud, reports Space.com.
And fire is impossible because there is very little oxygen in the thin atmosphere, which is mostly carbon dioxide.
The ESA said the same orbiter spacecraft, named Mars Express, and its predecessors have spotted similar clouds at least three times before.
The cloud structures all formed around the same time in the Martian year.
And that’s not a coincidence, scientists say.
ESA boffins reckon the cloud contains water ice and has been created by wind flowing along the side of the 12-mile-high, 150-mile-wide volcano.
The feature is what scientists call an orographic or lee cloud, which forms downwind of an obstacle.
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The cloud changes over the course of the day as atmospheric patterns on Mars vary.
Scientists studying hundreds of images of the cloud have noticed it grows over the course of the morning, stretching westwards along the equator for up to 930 miles.
It may also be affected by particles still in the atmosphere from the massive dust storm that engulfed Mars earlier this year.
In July the Mars Express orbiter detected what could be a massive underground lake of liquid water, raising hopes it could sustain life.