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Mars, of all the planets in our solar system, is the most similar to Earth. Some of the General characteristics of Mars are illustrated here and in associated resources, concentrating on those important to Martian meteorology,. Although its diameter is only 53% that of Earth, it has dramatic geological features ranging from a 3000 mile (~ 5,000 km) long canyon system and Martian volcanos, that rise 29 km, more than 90,000 feet, above the mean Martian surface. The axis about which Mars rotates, is inclined approximately 25.19° to its orbital plane, compared to Earth's 23.44°, its day, called a sol, is 24.66 hours, and its year is 669 sols. Currently it has a very thin, cold, mainly carbon dioxide, CO2, atmosphere about 1% as dense as Earth's, and some water-ice clouds but liquid water at the surface has yet to be conclusively demonstrated. However, Viking, Mars Surveyor, and Mars Odyssey observations demonstrate that large amounts of water ice are near the surface at high latitudes, and that half of the northern hemisphere might have been covered by an ocean for undetermined lengths of time early in the history of Martian evolution.
This Mars Orbiter Laser Altimeter topography map will be described in future updates. General characteristics are that the northern hemisphere is low and smooth, the southern is high and rougher, while giant craters, volcanoes and a canyon are present. The three white dots lined up in the top, left of the image are the Tharsis Volcanoes, while Olympus Mons, is the larger volcano to the north west of them, previously noted as being 90,000 feet above mean Mars level. Extending east from the base of the Tharsis volcanoes, is Valles Marineris, the canyon system roughly 5,000 km or 3,000 miles long. The deep blue crater in the southern hemisphere is Hellas.