Is Mars Really Red? A Physicist Explains the Science Behind Its Colour and More

Mars has been inspiring human imagination for millennia, mainly because it has a reddish colour, which earned it the title “Red Planet”. Its colour was associated by the ancient Romans with blood and war; thus, they named it after their god of war. The redness is the result, scientifically, of iron oxide — rust that coats the surface of Mars. Yet images of the surface produced by robotic probes have shown a more subtle spectrum. Much of the terrain appears more like dusty tan or rusty brown. Even the poles defy the planet's nickname, presenting as bright white due to water ice and frozen carbon dioxide that expand and contract with seasonal sunlight.

Mars Is Not Just Red: Telescopes Reveal a Complex Palette of Colors, Ice Caps, and Hidden Features

As per a recent article published by The Conversation and republished on Space.com, the iron-rich minerals of Mars have rusted, which is why it looks rusty. Like how iron and oxygen give blood its colour, Martian dust also rusts naturally. The polar caps, which are composed of frozen water and carbon dioxide and have a clearly different colour, are generally white. The sunshine prompts the layer of dry ice to sublimate and refreeze, making these caps expand and contract with the seasons.

Images taken by previous missions and rovers reveal Mars's palette, but telescopes and spacecraft equipped with ultraviolet and infrared cameras capture false colour images, leading to some confusion about the true colour of Mars.

Spectral observations, infrared and ultraviolet images, and the broader array of the electromagnetic spectrum are assisting scientists in investigate Mars' appearance, history, composition and potential past habitability.

Mars might still look red in the sky, but its actual narrative is rather more complex. Thanks to science and high-resolution cameras, our understanding of this neighbouring world is still unfolding.