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Mars - The Red Planet


Mars Global Surveyor view May 2003

Mars Global Surveyor view of Mars, May 2003


Basic Information:

  • MEAN RADIUS: 3388.0 km
  • MASS: 0.108 (Earth=1)
  • DENSITY: 3.94 (g/cm^3)
  • GRAVITY: 0.380 (Earth=1)
  • ORBIT PERIOD: 686.98 (Earth days)
  • ROTATION PERIOD: 1.026 (Earth days)


Named for the Roman god of War, Mars probably got this name due to its red color. It is sometimes referred to as the Red Planet. The name of the month March derives from Mars. Known since prehistoric times, Mars is still a favorite of choice for human exploration.

The density of Mars is about 30 percent less than that of Earth (3.94 g/cm3 vs. 5.52 g/cm3). Its core is probably similar to Earth's, mostly iron, with small amounts of nickel, but spacecraft mapping of its gravity field seem to indicate that its iron-rich core and mantle are a smaller portion of its volume than on Earth. Also, its smaller magnetic field than Earth, indicates a solid, rather than liquid core.

Mars' atmosphere is 95 percent carbon dioxide, nearly 3 percent nitrogen, and nearly 2 percent argon with trace quantities of oxygen, carbon monoxide, water vapor, ozone, and other trace gases.

The average temperature on Mars is about -55 C or -67 F. It can range from -133 C or -207 F at the winter pole to almost 27 C or 80 F on the day side during summer. Orbiting 227,940,000 km (1.52 AU) from Sun, the Martian year is nearly two Earth years, while its day is only about half an hour longer than Earth's.

Mars has two tiny satellites which orbit very close to the surface: Phobos

  • Distance: 9000 km
  • Radius: 11 km
  • Mass: 1.08e16 kg
  • Discoverer: Hall
  • Date: 1877
  • Distance: 23000 km
  • Radius: 6 km
  • Mass: 1.08e15 kg
  • Discoverer: Hall
  • Date: 1877

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