Study reveals Mars's red hue comes from mineral formed in ancient water

For as long as humans have looked skyward, Mars has burned red against the dark — a color long assumed to be the mark of a dead, desiccated world. A 2025 study now suggests that hue was painted not by dryness, but by water: ferrihydrite, an iron mineral born in cool liquid, appears to be the primary source of Mars's famous coloration, implying the planet held water far earlier in its history than science had supposed. In recoloring our understanding of Mars's past, the finding quietly expands the window in which life might once have been possible.