Which planet is known as the Red Planet?

Mars is known as the Red Planet due to its reddish appearance, which is primarily caused by iron oxide, commonly known as rust, that coats its surface. This unique coloration has intrigued humans for centuries and led to its designation as the Red Planet. Observations from Earth, as well as data collected by various missions to Mars, have confirmed this characteristic, making it easily distinguishable in the night sky compared to other planets.

The other planets mentioned do not share this distinctive red hue. Venus is often referred to as Earth’s "sister planet" because of their similar size, while Earth is known for its blue oceans and green landmasses. Mercury, being the closest planet to the Sun, has a grayish, heavily cratered surface that lacks the distinct iron oxide found on Mars. These differences highlight why Mars is specifically identified as the Red Planet.