Mars has fascinated humans for thousands of years, partly because of its distinctive reddish glow. The reason behind that colour is surprisingly down-to-earth: Mars is literally rusty.
It’s all about iron
The Martian surface is rich in iron. Over billions of years that iron reacted with oxygen — the same process that turns an old nail orange — forming iron oxide, better known as rust. A fine layer of this reddish dust coats the entire planet.
Dust storms spread the colour
Mars is famous for enormous dust storms that can cover the whole globe. These storms lift the rusty dust high into the thin atmosphere and spread it everywhere, giving the planet its uniform reddish-orange tone — even the Martian sky often looks butterscotch-coloured.
Not the same red everywhere
Up close, Mars isn’t a single shade of red. Rover photos show browns, tans, and even darker, almost grey rocks where the dust has blown away. The vivid red we see from Earth is mostly that thin coating of oxidised dust catching sunlight.
So the next time you spot Mars as a reddish dot in the sky, you’re really looking at an entire planet that has slowly rusted over billions of years.
Photo: NASA / public domain.