This colour composite from infrared, green and blue channel images shows a zone of collapse features on the southern flank of the giant shield volcano Arsia Mons. The total height difference in the land surfaces in this scene is about 7 kilometers, and some individual collapse pits have a depth of more than 2 kilometers. The pits probably formed when lava erupted from the side of Arsia Mons. When lava, or molten rock, finds its way to the surface, it produces several veins and chambers. These slowly empty as the lava erupts and runs down the volcano flanks. Some of the lava reaching the surface cools down and becomes solid, often building a roof over the emptied chamber. The resulting voids collapse due to the weight of the overlying material. At several places, the walls of the pits have been modified by later landslides. The overall trend of the collapse zone runs from the south-west to the north-east, following exactly a giant zone of crustal weakness in the Tharsis region, along which the three large Tharsis volcanoes are aligned. Arsia Mons is the southernmost of these volcanoes. It is 435 kilometers in diameter, almost 20 kilometers high, and the summit caldera is 116 kilometers wide.
The images that were used to create this colour composite were taken on April 2, 2004, by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft. The images were taken from an altitude of 400 kilometers and cover an area of about 80 by 105 kilometers.
The colour composite has not yet been officially released by ESA.
Image Credit: ESA/DLR/FU Berlin (G. Neukum)/astroarts.org