Mars is often called the "red planet." It's red because its surface is covered with rusted particles of iron. Like the Earth, Mars has polar ice caps, mountains, craters, plains, canyons, and summer and winter seasons. Scientists think that liquid water once flowed on the surface of Mars when it was warmer. But today there are no signs of life or water on Mars' rocky surface.

Location: 4th planet from Sun
Diameter: 4,200 miles
Number of Moons: 2
Average Distance from Sun: 140,000,000 miles
Average Surface Temperature: summer 32 degrees F, winter -150 degrees F
Orbital Period: 687 days
Characteristics: volcanoes and deep canyons cover this red planet's rocky surface

Image credits: main image: courtesy of JPL/MSSS, and NASA.