Mars Fact File

Mars is the fourth planet from the sun and is almost half the size of Earth. Mars orbits the sun at an average distance of 227,936,640 km. A full orbit around the sun takes around 687 Earth days. At 24.7 hours, a day on Mars is only slightly longer than a day on Earth.

The surface of Mars has undergone many changes due to volcanism, impacts from other bodies, movements of its crust, and atmospheric effects such as dust storms. The dust storms can reach tremendous proportions. Recent Hubble images have shown the whole surface of the planet covered with a massive dust storm. Polar ice caps are present on Mars. These ice caps increase and decrease in size depending on the season.

Mars has some remarkable geological characteristics, including the largest volcanic mountain in the solar system, Olympus Mons (27 km high and 600 km across); volcanoes in the northern Tharsis region that are so huge they deform the planet's roundness; and a gigantic equatorial rift valley, the Valles Marineris.

Mars has two small moons, Phobos and Deimos. It is uncertain how they formed, but it is believed that they may be asteroids that have been snared by Mars' gravity.

Mars: Facts & Figures

  • Average Distance from the Sun: Metric: 227,936,640 km
  • Perihelion (closest): Metric: 206,600,000 km
  • Aphelion (farthest): Metric: 249,200,000 km
  • Equatorial Radius: Metric: 3,397 km
  • Equatorial Circumference: Metric: 21,344 km
  • Mass: 641,850,000,000,000,000,000,000 kg
  • Volume: 163,140,00,000 km3
  • Density: 3.94 g/cm3
  • Surface Area: 144,100,000 km2
  • Equatorial Surface Gravity: 3.693 m/s2
  • Escape Velocity: 18,072 km/h
  • Length of Day: 24.62 hours
  • Length of Year: 686.93 Earth days
  • Mean Orbit Velocity: 86,871 km/h
  • Orbital Eccentricity: .0934
  • Orbital Inclination to Ecliptic: 1.8 degrees
  • Equatorial Inclination to Orbit: 25.19
  • Orbital Circumference: 1.366,900,000 km
  • Min/Max Surface Temperature: -87 to -5 °C
  • Atmospheric Constituents: Carbon Dioxide, Nitrogen, Argon
  • Number of Moons: 2

Source: NASA