Mars is easily identifiable in the night sky by its prominent red hue. Thanks to the fleet of spacecraft that have studied the planet over the last decades, we know that this red color is due to rusted iron minerals in the dust.

Thanks to new research techniques published today, scientists say that "our understanding of why Mars is red has been transformed."

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.

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.