Tharsis Tholis towers 8 km above the surrounding terrain. Its base stretches 155 x 125 km and what marks it out as unusual is its battered condition.
The main feature of Tharsis Tholus is the caldera at its centre. It has an almost circular outline, about 32 x 34 km, and is ringed by faults where the caldera floor has subsided by as much as 2.7 km.
The image was created using a Digital Terrain Model (DTM) obtained data taken by the High Resolution Stereo Camera on ESA’s Mars Express spacecraft during four orbits of Mars: 0997, 1019, 1041, 1052 between 28 October and 13 November 2004.
Elevation data from the DTM is colour coded: purple indicates the lowest lying regions and beige the highest. The scale is in metres.
Elevation data from the DTM is colour coded: purple indicates the lowest lying regions and beige the highest. The scale is in metres.
By Earthly standards, Tharsis Tholus is a giant, towering 8 km above the surrounding terrain, with a base stretching over 155 x 125 km.
Yet on Mars, it is just an average-sized volcano. What marks it out as unusual is its battered condition.
Shown here in images taken by the HRSC high-resolution stereo camera on ESA's Mars Express spacecraft, the volcanic edifice has been marked by dramatic events.
At least two large sections have collapsed around its eastern and western flanks during its four-billion-year history and these catastrophes are now visible as scarps up to several kilometres high.
The main feature of Tharsis Tholus is, however, the caldera in its centre.
It has an almost circular outline, about 32 x 34 km, and is ringed by faults that have allowed the caldera floor to subside by as much as 2.7 km.
It is thought that the volcano emptied its magma chamber during eruptions and, as the lava ran out onto the surface, the chamber roof was no longer able to support its own weight.
So, the volcano collapsed, forming the large caldera.
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