Mars appears red due to iron oxide (rust) on its surface. This review summarises current understanding of the mineralogical and atmospheric factors contributing to the planet's distinctive colouration.
Mars has been observed as a reddish planet since antiquity. The colour arises primarily from ferric oxide minerals distributed across the surface and suspended in the atmosphere as dust.
A narrative review of published spectroscopic and rover-based mineralogical studies was conducted.
Iron oxide, predominantly hematite and goethite, accounts for the characteristic red-orange hue. Fine dust particles suspended in the thin Martian atmosphere contribute an additional reddish tint to the sky.
The red colour of Mars is a well-documented consequence of surface iron oxidation. Future in-situ studies may further characterise regional colour variation.