Introductory Astronomy: The Planet MARS

Basic Facts:
Distance from Sun: 1.38 - 1.66 AU
Period of revolution about Sun: 687 days
Period of rotation: 24.6 hours
Radius: 0.53 Earth radii
Mass: 0.11 Earth masses
Average Density: 3.9 g/cm^3
Magnetic Field: none detected
Surface features: impact craters, shield volcanoes, fault/rift valley, runoff channels
Atmosphere: 95.3% CO2, 2.7% N2, surface pressure: 1/150 of Earth's
Temperature: 80 to -190 degrees Farenheit

In many ways, Mars is much more like Earth than Venus. A day on Mars lasts only 37 minutes longer than on Earth, frozen water is clearly seen on its surface, and there is evidence that there was liquid water on Mars' surface in the past. However, there are many differences as well. Mars' thin atmosphere (mostly carbon dioxide, like Venus') is not thick enough to shield it from impact craters nor to sustain liquid water at the present time.

Many people believe that life has a good chance on this planet, and that we should try to terraformMars. (This means that we should try to make Mars habitable for plant (and maybe someday human) life.) To learn more about what terraforming is and its pros and cons, click here.

The Martian surface is heavily cratered and shows signs of both past erosion and volcanic activity (for example, the gigantic volcano Olympus Mons ). There are also signs of landslides and fault lines, which show that plate tectonics played a role in Mars' past. Its lack of a magnetic field suggests that Mars does not have much of an iron core. A view of the Martian surface.

Unlike Mercury and Venus, Mars does have two moons: Phobos and Deimos. Because they are small and irregular in shape, some scientists believe that these moons may be captured asteroids.

To learn more about Mars, click here.