Mars, often referred to as the red planet because of the color of rusty iron in its surface, is the most-explored body in our solar system. Twenty spacecraft and four rovers from earth have visited this cold desert planet so far.

Facts about Mars:

Astronomers once believed Mars had seas and regions of vegetation. They now understand sandstorms cause the light and dark areas visible on the planet's surface.

Evidence of erosion caused by flowing water implies Mars was once much warmer and had a thicker atmosphere.

Mars has canyons and volcanoes, just like Earth. It cannot currently support life because of its thin atmosphere and limited amounts of oxygen and water vapor. 

Mars statistics:

• Distance from the sun: 228 million km (142 million mi)

• Diameter: 0.53 x Earth

• Mass: 0.107 x Earth

• Time for one full orbit ("year"): 1.88 Earth years

• Time for one full rotation ("day"): 24.7 Earth hours

• Elliptical, egg-shaped orbit and two moons