Because of the transparent atmosphere, Mar’s surface can be observed directly, unless its obscured by a passing dust storm, cloud, or an atmospheric haze. The surface formations that may be observed through a telescope are divided into three groups, differing by their albedo and colouring: reddish orange places called ‘deserts’ or ‘continents’, gray areas called ‘lakes’, ‘seas’, etc.., and the last of all the dazzling white polar caps. Unlike the seas on the Moon, the dark areas on Mar’s surface vary in albedo and size, as well as colour, according to the seasons of the year, usually after a dust storm. Also the size of the polar caps depend on the season of the year. The caps may be seen with the use of a small telescope, and the same is also true for the darkest formations on the surface such as Mare Acidalium, Syrtis Major, Mare Sirenum, and others.
Spaceprobes that explored mars during the seventies led to more detailed maps of the planets surface. Close-up views of the albedo formations do not correspond to a specfic type of surface, as in the cases found on the Moon. A large part of the southern hemisphere of Mars and also the smaller part of the Northern hemisphere are heavily marked with craters, like our Moon’s continents. This cratered area is geologically the oldest area, and includes dates from a period of heavy bombardment. The huge basin Hellas Planitia is 1,500 km in diameter and 6 km deep. The northern hemisphere is mainly flat. There are fewer craters located in this area and the predominant type are splash craters. Two large shield volcanoes- Hecates tholus and Elysium Mons- rise above the plain area Elysium Planitia. About 200 km away from the crater Mie is the area where Viking Lander 2 landed on the surface on the 3rd of September, 1976, finding Mars to be a desert filled with stones and blanketed with dust.
The craters on Mars are named, such as the craters on the Moon, after prominent technologists and scientists, as well as artists and travellers. Smaller craters shown on more detailed maps are named after villages and towns on Earth.
Around the equator in the planet's western hemisphere there are two interesting regions, the largest of their kind in the Solar System: the Valles Marineris complex of canyons and the Tharsis volcanic region.
The main volcanic region of Mars is the Tharsis range. The large volcanoes of Mars look like the shield volcanoes one could find in Hawaii. The volcanoes located in this region are of record dimensions. The volcano Olympus Mons has a complex caldra that measures 25 km above the mountain and 80 km across. The diameter of the mountain’s circular base is approximately 500 km. Remnants of old lava flows can be traced hundreds of kilometers away from the base of the mountian. These huge deminsions indicate that the volcano had been active for many thousands of millions of years, and it is possible that it may still become an active volcano today. Bright clouds of crystal ice clouds form above the mountain, mostly in the spring.
Tharis is the largest volcanic area on Mars and in the past vast quantities of lava flowed over thousands of kilometers of surface forming a covering of increasing thickness. It gradually built a circular region as high as 10 km and a radius of more than 1000 km. The volcanic activity of unprecedented proportions played a very important role in the shaping of the martian landscape.
The largest formation of complex tectonic origin is Valles Marineris complex systems of rilles, faults, and fissures in the planet’s crust. The largest formation of tectonics origin is the Valles Marineris array of canyons, named after the spacecraft Mariner 9, that in the years 1971- 1972 mapped the whole planet in detail for the first time. The formation extends eastward 45000 km from the centre of the tharsis range in parallel rows of steep walled canyons reaching up to 200 km across. On the walls and floors of such canyons one can find numerous traces of huge land slides. The loose materials are then further shifted and shaped by the martian winds.
The region of Chryse Planitia is where the Viking Lander 1 touched down on the 20th of July, 1976. The probe's cameras showed a stony desert with small sand dunes. Biological analysis of the soil taken didn’t reveal any traces of life.
Here are a few links on the web with more information about Mars:
Mars Exploration Education Home Page!
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