geology of mars introduction image
Global Properties
Dust Storms
Canyons & Caps
Viking Landers
Internal Structure

From Earth-based observations, Mars appears as a red planet. It is the iron-oxide that gives the planet its reddish appearance. In other words, Mars is a rusty planet. Like the Moon and Mercury, there are both light-colored and dark-colored areas on Mars as shown in Figure 1.6. After all the flyby and orbital missions of NASA, a complete global coverage of Martian surface has become available. It is now clear that the light-colored areas represent the heavily cratered highlands, whereas the dark areas are the relatively smooth lowlands. One striking feature, however, is that the light and dark areas take on a hemispheric distribution. If the highlands are considered the equivalent of continents on Earth, and the lowlands are the equivalent of ocean floors, one hemisphere of the Martian surface would become a continent and the other hemisphere would be covered with an ocean. This is a very interesting feature, considering that two hundred million years ago, there was also only one super-continent and one giant ocean on Earth.

 figure 1.6

figure 1.7

At present, no good explanation exists to account for the hemispheric distribution of these two distinct landforms. The Mars Global Surveyor was able to complete a global topographic mapping using altimetry measurements in 1999. A detailed surface topography map is given in Figure 1.7. In this map, the areas with the warm colors (i.e., red, orange, and yellow) are the heavily cratered southern highlands and the areas with cool colors (i.e., blue and green) are the lowlands. Both Viking landers landed on the smooth northern hemisphere.

The southern highland of Mars is somewhat similar to the heavily cratered terrain of Mercury or the highlands on the Moon, where craters of all sizes and shapes dominate the landscape. Most of this highland area, except some interior basin floors, are, on average, more than 1 km above the mean radius of the planet. There are also a few shield volcanos that can be found in the southern highland. In addition, this ancient battered surface has some large channels that appear to have been carved by rivers or huge floods. These flow channels give the Martian surface a decidedly different appearance from that of the Moon or Mercury.

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geology of mars