The red planet's colour

Iron oxide makes Mars look blood-like, but there is a lot more to it.

- By David Joffe

People from cultures throughout the world have been looking at Mars since ancient times. Because it appears reddish, it has often been called the red planet.

The English name for the planet comes from the Romans, who named it after their god of war because its colour reminded them of blood. In reality, the reddish color of Mars comes from iron oxide in the rocks and dust covering its surface.

Your blood is also red because of a mixture of iron and oxygen in a molecule called haemoglobin. So, in a way, the ancient connection between the planet Mars and blood wasn't completely wrong.

Rust, which is a common form of iron oxide found here on Earth, also often has a reddish colour.

In my current research on exoplanets, I observe different types of signals from planets beyond Earth. Lots of interesting physics goes into how researchers perceive the colours of planets and stars through different types of telescopes.

Observing Mars with probes

If you look closely at pictures of Mars taken by rovers on its surface, you can see that most of the planet isn't purely red, but more of a rusty brown or tan colour.