Mars is a terrestrial planet like Earth, Venus and Mercury which means it is made of minerals, metals and other elements that make up rock and it has a solid surface. The large amount of iron oxide on the surface gives Mars its reddish colour, which is why it is often called the Red Planet. It has two tiny, irregular shaped moons, Phobos and Deimos.
The diameter of Mars is about half the diameter of Earth and because of its smaller size and mass the surface gravity on Mars is about 40% of that on Earth. Mars has a thin atmosphere mainly consisting of carbon dioxide (95%), argon (2%) and nitrogen (2%).
Mars is home to the largest volcano (called Olympus Mons) and the largest canyon (called Valles Marineris ) in the Solar System. You should be able to see the canyon on the rotating image by comparing it with the image of Valles Maineris below.
Huge dust storms can cover the entire planet which makes the surface look different sometimes. Mars has polar ice caps mostly made of frozen water and it looks like there may have been lakes on the surface a long time ago. If there was liquid water on Mars in the past it is possible that life could have existed there.
Since the arrival of Mariner 4 back in 1964, lots of spacecraft have been to Mars. Two spacecraft are on the surface, they are called Opportunity and Curiosity. One of the things they are looking for is evidence of life on Mars.