Named after the Roman god of war, the red appearance of Mars is caused by iron oxide that covers much of its surface. The fourth planet shows volcanoes, valleys, deserts and polar ice caps much like those on Earth. A day on Mars is almost the same as Earth: 24h 37m 22s.

Channels on the surface of Mars are very similar to river channels on Earth. This suggests that liquid water once flowed on the surface of Mars when it had a thicker atmosphere. Today, much of the Martian atmosphere has been eroded away by the solar wind, and water can no longer exist on the surface due to the low atmospheric pressure. Large amounts of water ice are thought to be trapped in a thick permafrost layer below the surface. Radar data from satellites support this concept.

Mars is also home to the largest volcano in the Solar System – Olympus Mons. This shield volcano would cover the state of Arizona, and is so tall it extends out of the Martian atmosphere. With a pressure suit, you could hike from the surface of Mars to space! Now that's a field trip.

For years people thought Mars was inhabited. Percival Lowell build an observatory in Flagstaff, AZ to study Mars and wrote many books about life on Mars. H.G. Wells wrote War of the Worlds, a book about a Martian invasion. A radio play in 1938 based on the book caused widespread panic. Today we hope to find bacteria on Mars.

Mars is the most explored of the planets. Currently the Curiosity rover is the largest on Mars. Several orbiters are also active around the planet and more are on their way.

  • Mars
  • Mars Closeup
  • Mars Symbol
Orbit Specifications
Semi-major axis 2.28 x 108 km
1.5237 AU
Eccentricity 0.09
Orbital Period 686.971 days
Physical Characteristics Specifications
Mean radius 3,390 km
0.533 Earths
Mass 6.4185 x 1023 kg
0.107 Earths
Mean density 3.93 g/cm3
Surface gravity 3.71 m/s2
0.38 g
Axial tilt 25.19°