The Mars Express, equipped with cameras, in the orbit of Mars of the European Space Agency, holds tight tabs about the mysterious “elongated cloud” that appears over the 20-kilometer volcano Arsia Mons near the equator of the Red Planet.
A spaceship, like it, has been following the evolution of a strange cloud since 2009. Now new images discovered this week by ESA show that the cloud is persisting.
The scans suggest that the mysterious cloud has nothing to do with volcanic activity – the last time Arsia Mons was active was about 50 million years ago, according to NASA. Instead, scientists suspect it is a cloud of water ice flowing down the sloping sides of the volcano.
The cloud, as seen in recent images taken on July 17 and 19 by the Mars Express Visual Monitoring Camera (VMC), appears to be up to 1,800 kilometers long.
Fast daily cycle
And it also doesn’t last long. Every Martian year, around the time of the southern solstice of Mars – the equivalent of December 21 here on Earth – the cloud grows for several hours every day and quickly fades again.
“This elongated cloud is formed annually by the Martian year during this season around the southern solstice and repeats for 80 days or more, after a rapid daily cycle,” said Jorge Hernandez-Bernal, Ph.D. in the ESA report. “However, we still don’t know if the clouds are always so impressive.”
This unusual observation was made possible by the VMC’s wide field of view and highly elliptical orbit.
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