What are the unique features of Mars?

The planet Mars is home to Olympus Mons, the tallest volcano in the solar system. Valles Marineris, also located on Mars, is the largest known canyon found on any planet within the solar system.

Mars is the fourth planet from the sun. Its bright red color is due to the iron-rich minerals found on its surface. Temperatures on Mars are too cold for liquid water to exist for any length of time, but frozen water can be found at both poles. Mars is only about half the size of the Earth, but it has enough mass to retain a thin atmosphere.