Mars

Mars is the 4th planet in the Solar System.

Surface
The red-orange appearance of the Martian surface is caused by iron(III) oxide, more commonly known as rust.

Life
The current understanding of planetary habitability—the ability of a world to develop and sustain life—favors planets that have liquid water on their surface. This most often requires that the orbit of a planet lie within the habitable zone, which for the Sun currently extends from just beyond Venus to about the semi-major axis of Mars.