Question

why mars is called red planet ?

Answer 1

Mars is called red planet due to its reddish appearance -- this appearance is due to the surface material containing large amounts of iron oxide.

Answer 2

Mars is often called the 'Red Planet' because it appears in the sky as an orange-red star. The colour caused the ancient Greeks and Romans to name it after their god of war. Today, thanks to visiting spacecraft, we know that the planet's appearance is due to rust in the Martian rocks.