Martian dust is mostly rust. Mars’s famed color has captivated humankind for centuries, earning its nickname of the ‘Red Planet’. Romans named Mars for their god of war because its colour was reminiscent of blood, while Egyptians called it ‘Her Desher’, meaning ‘the red one.’ CREDIT: A.Valantinas.

For centuries, Mars has captivated scientists and the public alike with its striking red hue. Early astronomers speculated that the planet’s color came from iron-rich minerals, much like rust on Earth.

New research shows that the red dust on Mars contains ferrihydrite, a water-rich iron oxide. It's evidence that the planet rusted in water.