When we consider the history of Martian observations it is easier to see why this planet is considered a kindred spirit to the Earth. Shortly after the invention of the telescope astronomers viewing Mars were able to determine that Mars rotated on its axis in about 24 hours, a characteristic of Earth. They were also able to see that Mars had polar caps. By observing these polar caps astronomers were able to determine that the axis of Mars was tilted about 25 degrees (the axis of the Earth is tilted about 23.5 degrees). The similarities brought about a sense of familiarity with the planet Mars.

Further observations showed us that surface changes took place as the seasons on Mars changed. The coloration of the surface changed causing some to speculate that plant life was growing on Mars during the spring and summer months. This was a major trigger for the idea of life on Mars. In later years, when it was thought that canals existed on Mars, this idea went one step further. It was believed that the canals on Mars were created to irrigate plant life on Mars. If water on Mars was so difficult to come by that these huge irrigation canals needed to be used than certainly the water on Earth was something the Martians would want. The rest is history and science fiction.

We now know the canals to be optical illusions caused by the various colorations on the Martian surface. In addition, satellites have not shown any signs of life on Mars. Signs of water have been discovered in the forms of dried up river beds, fog, permafrost, and ice in the polar caps. Liquid water in the river beds has probably not existed for millions of years. Ice in the polar caps is accompanied by frozen carbon dioxide (dry ice). The change in surface color during the seasons is due to dust storms turning over the Martian soil.

Mars is often referred to as the red planet. This reddish color is apparent even from Earth based observation. This color comes from the surface composition of Mars which contains oxidized iron (rust).

The surface of Mars also shows volcanoes. The volcanoes have been extinct for a very long time. It is likely these volcanoes are responsible for the thin atmosphere of Mars. Volcanoes on Mars are different from volcanoes on Earth. Volcanoes on Mars are very large. Olympus Mons (seen below) is the largest known volcano in the solar system. Martian volcanoes also show only a single vent. Earth based volcanoes generally show multiple vents due to plate tectonics. Therefore Mars probably has little to no plate tectonics.

In contradiction to this lack of geological activity is a large Canyon on the surface of Mars. This Canyon is referred to as Valles Marineris. If placed on the Earth, Valles Marineris would stretch across the United States from coast-to-coast. The Grand Canyon is dwarfed in comparison.

Mars is also known to have two moons. These two moons however, are very small and are likely to be captured asteroids and not true moons in the sense of the word. These moons are named Phobos and Deimos.

This page was last updated on 06/13/01.