TOPOGRAPHY
| The surface of Mars is covered by volcanic and impact craters, which are similar to those, found on Mercury. A feature common with Earth is the fault rifts and seismic fracture zones. There are canyons on the surface, the largest one, called Mariner Valley, stretching east by southeast. In addition, the surface is marked by vast networks of dry riverbeds and huge channels. This gives evidence of the presence of water in the past. Although there is no free water on Mars today, there is probably subsurface water almost everywhere locked in the ground as ice. |