The Mysterious Red Planet, Mars
Thin, carbon dioxide clouds dot the surface of Mars from Olympus Mons on the left, across the Tharsis Highlands. A short distance from veiled Olympus Mons (the tallest volcano in the Solar System) stand the three large calderas of Tharsis Montes ranging from the Northeast to Southwest across the western highlands. The southernmost is Arsia Mons, the central peak is Pavonis Mons, and the northernmost is Ascraeus Mons. None of these three stand as high as Olympus Mons, despite the greater starting elevation of the highlands.
Just below the middle, in the center of this image, starts the Valles Marineris—a deep gash in the planet's surface which runs eastward from here, one-fourth of the way around Mars.
The atmosphere is extremely thin, roughly equivalent to that on Earth at an altitude 21 miles above sea level. No surface water exists, but there is evidence that the surface has been eroded by liquid water in the remote past. And so far, no indigenous life has been found on Mars.
Aphelion (farthest from Sun): 155 million miles.
Perihelion (closest to Sun): 128 million miles.
Orbital Period: 686.971 days.
Mass: 0.107 times that of Earth.
Diameter: 0.533 times that of Earth.