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Characteristics of Mars' Surface

Mars is the fourth planet from the sun. Since the National Aeronautics and Space Administration's Mariner 4 spacecraft became the first to achieve a successful flyby of Mars and send back images of its surface in 1965, many others have flown by, orbited and landed on the planet. These missions have yielded data that have broadened astronomers' understanding of conditions on the Martian surface. This information is crucial for NASA's potential manned missions to Mars.

Soil
- Virtually all of Mars is covered in a reddish, fine-grained dust. The rustlike color, which is visible from Earth, is due to the high presence of hematite, a type of iron oxide, in its soil. The crimson color is reminiscent of fire and blood, which led to Mars being named after the Roman god of war.
Topography
- The landscape on Mars is diverse. The northern hemisphere features low-lying plains that are among the smoothest surfaces in the solar system. Elevation on Mars varies drastically, due to canyons and mountains that are much deeper and higher than those on Earth. The deepest canyons on Mars are five to six miles deep. Some of the largest volcanoes in the solar system are also found on Mars, including the 16-mile-high Olympus Mons, the solar system's tallest known volcano. The Martian surface is also covered with impact craters of various sizes caused by meteoroids.
  
  There is presently no liquid water on Mars, though channels, gullies and valleys on its surface may have been caused by water erosion at some point in the planet's history. Ice caps have been discovered on the Martian poles, though unlike Earth's polar caps, those of Mars are believed to contain frozen carbon dioxide.
Atmosphere
- Mars' atmosphere is extremely thin compared to Earth's and is composed primarily of carbon dioxide. Other gases, including nitrogen, carbon monoxide, argon and water vapor are present in small amounts. Ultraviolet radiation from the sun reaches the Martian surface in the absence of an ozone layer.
Climate
- Temperatures on Mars are much colder than on Earth. They vary from minus 200 degrees Fahrenheit at the highest altitudes to between minus 20 and minus 40 degrees F on the surface. The average temperature is minus 63 degrees F.
  
  Winds on Mars are for the most part gentle with occasional gusts. Dust storms engulf the entire planet at times. The presence of dust in the atmosphere leads to temporary increases in temperatures on the surface. Haze and fog occur in the mornings.

Astronomy