Space World / fourth planet from the Sun / Mars planet

Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury.
View on Maps: google.com/maps/space/mars
Radius: 3,390 km
Mass: 6.39 × 10^23 kg (0.107 M⊕)
Surface pressure: 0.636 (0.4–0.87) kPa; 0.00628 atm
Moons: Phobos, Deimos
Did you know: On its one-year anniversary, the NASA's Curiosity Rover sang the "Happy Birthday" tune to itself on Mars. 

Mars The fourth planet from the sun, is a cold, dusty place. The dust, an iron oxide, gives the planet its reddish cast. Mars shares similarities with Earth: It is rocky, has mountains and valleys, and storm systems ranging from localized tornado-like dust devils to planet-engulfing dust storms. It snows on Mars. And Mars harbors water ice. Scientists think it was once wet and warm, though today it’s cold and desert-like.

Mars' atmosphere is too thin for liquid water to exist on the surface for any length of time. Scientists think ancient Mars would have had the conditions to support life, and there is hope that signs of past life — possibly even present biology — may exist on the Red Planet.

Discovery: Known to the ancients and visible to the naked eye
Named for: Roman god of war
Diameter: 4,217 miles (6,787 km)
Orbit: 687 Earth days
Day: Just more than one Earth day (24 hours, 37 minutes)
Related:
More Mars Facts
Mars Pictures
NASA Solar System Exploration: Mars
Close-up of Jupiter's Great Red Spot as seen by a Voyager spacecraft.
Close-up of Jupiter's Great Red Spot as seen by a Voyager spacecraft.
Credit: NASA/JPL-Caltech