These and other missions have allowed detailed topographical maps to be compiled, as well as studying the changes in the gravitational force exerted by the planet.
In fact, using geophysical models, they found evidence that the entire area is supported by a mantle plume of hot material between 95 and 285 kelvin, warmer than its surroundings.
This volcanism on Mars has similarities but also presents differences to that on Earth. The same process of mantle plumes and hot spots occurs in places like Hawaii or the Canary Islands.