The planet known as the Red Planet is Mars. Mars gets its nickname due to its reddish appearance, which is caused by iron oxide (or rust) on its surface. This iron oxide gives the planet a distinct reddish color when viewed from Earth.

Mars' reddish hue can be seen clearly even with the naked eye. When observing Mars through a telescope, the planet's surface features, such as its dusty deserts, canyons, and volcanic regions, become more apparent. These features contribute to the overall reddish tone of the planet.

One of the most famous examples of Mars' red color can be seen in the Martian dust storms. These storms, which can cover the entire planet, kick up fine dust particles into the atmosphere, further enhancing the red coloration of the planet.

References:

1. NASA. (n.d.). Mars. Retrieved from https://solarsystem.nasa.gov/planets/mars/overview/
2. National Geographic. (2021, February 18). Mars. Retrieved from https://www.nationalgeographic.com/science/space/solar-system/mars/