Mars is the fourth planet from the Sun and the second smallest (after Mercury), with a diameter of 6794 kilometers (53% of that of Earth). Mars is one of the four terrestrial planets (planets having a solid surface). If you were standing on Mars, you would weigh just 38% of what you weigh on Earth.
Mars orbits the Sun once every 1.8809 Earth-years, with an orbital eccentricity of 0.093—the greatest eccentricity of any planet except Mercury. It averages 1.52 times as far from the Sun as does Earth.
Mars rotates about its axis prograde (in the same direction as its solar orbit) once every 24 hours 37 minutes 23 seconds. This is closer to one Earth-day than the rotational period of any other planet. Its axis is tilted by 25.19° relative to the perpendicular of its orbital plane; this is closer to Earth's axial tilt of 23.45° than that of any other planet.
Scientists of 19th century believed that life had gained a toehold on Mars.Canals were discovered on the red planet by Italian astronomer,Giovanni Schiaparelli in 1887.These appeared as markings on the surface of Mars.Scientists believed that these canals are constructed by intelligent beings to divert water from polar regions to the desert areas. Like Earth,Mars had seasons .In spring and summer,the colour of the dark areas of the Mars changed from bluish green to yellow.So,It was suspected that plant life thrived on Mars.However,the Mars probe,Mariner 4 sent home pictures of a lifeless planet.Ultraviolet radiation from the sun coupled with the special nature of soil prevents Life from gaining on toehold on Mars.
Phobos is the larger and closer of Mars's two satellites, with a diameter of just 26 kilometers along one axis and just 18 kilometers along another axis. Of all the moons that are their planet's largest, Phobos is the smallest both in absolute terms and relative to its planet's size.
Deimos has a diameter of 16 kilometers along one axis and 10 kilometers along another.