Mars is the fourth planet from the Sun and the second smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is often described as the "Red Planet" because the iron oxide prevalent on its surface gives it a reddish appearance.[14] Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons.
Since 6 August 2012, there have been two scientific rovers on the surface of Mars beaming signals back to Earth (Opportunity of the Mars Exploration Rover mission, and Curiosity of the Mars Science Laboratory mission), and three orbiters currently surveying the planet: Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter. Two orbiters launched in November 2013, Mars Orbiter Mission and MAVEN, are currently on their way to Mars.
