Mars Express HRSC image of Mars centered over the Tharsis volcanic region. Near center is the extremely low-profile shield volcano Alba Mons, the largest volcano in the Solar System in terms of area. At bottom right is Ascraeus Mons, another shield volcano with a summit region approximately 12 km above the surrounding plains. A small cluster of volcanic edifaces is visible just above Ascraeus Mons. The Valles Marineris and Noctis Labyrinthus canyon systems are visible along the horizon.
This image was taken near the northern summer solstice. With the solstice came the annual retreat of the north polar cap, which was nearing peak sublimation rate when this image was taken. The CO2 and water vapor released fueled several cold fronts and dust storms in the northern polar plains. In addition, much of the equatorial region is swathed in the Aphelion Cloud Belt, a seasonal feature that forms when Mars is around its furthest from the Sun. The reduced sunlight lowers the vapor temperature just enough to allow water vapor to condense into clouds around the equatorial regions.
This image was taken during Mars Express' 18,508th orbit of Mars, October 30, 2017.
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