What causes Mars’s characteristic red color?

Iron oxide causes Mars’s characteristic red color.

Mars’s surface materials contain iron-bearing minerals. When these minerals react with oxygen and water, they can form iron oxides, commonly described as rust. Fine particles of this oxidized material are spread across the surface and suspended in the atmosphere, giving the planet its familiar reddish appearance.

The red dust is not a single continuous coating. It mixes with darker volcanic rocks and covers large areas in varying thicknesses. Dust storms can lift it high into the atmosphere, sometimes creating planet-wide haze.

Mars’s color does not mean that liquid water is currently rusting the entire planet in the same way iron rusts on Earth. Scientists study several possible pathways for oxidation, including ancient water-related processes and reactions involving atmospheric chemistry. The key identifying mineral family is iron oxide.