Why Is Mars Red?

Scientists have long believed that Mars' distinctive hue comes from iron particles being rusted... but by what? A new study suggests that it wasn't water that turned the Red Planet red, but wind.

According to experiments carried out by Jonathan Merrison of Aarhus University in Denmark, the color may be the result of magnetite and quartz particles colliding as the result of being blown about the planet's surface, with each collision exposing surfaces of the quartz that oxidize the magnetite. After tests artificially creating similar circumstances, Merrison and his team now suggest that "a few thousand years" worth of such collisions would've resulted in Mars becoming the color it is today.

Wind, not water, may explain Red Planet's hue [New Scientist]