Why is Mars Red? New Research Suggests Ferrihydrite is the Key

In a recent study, Dr. Janice Bishop of the SETI Institute, along with postdoctoral researcher Adomas Valantinas from Brown University, propose that Mars' characteristic red hue is primarily due to ferrihydrite—a water-rich iron oxide mineral—rather than the previously assumed hematite. Analyses of data collected by Martian orbiters, rovers, and laboratory experiments showed that ferrihydrite closely matches the composition of the dust covering Mars' surface. Ferrihydrite typically forms in environments abundant in cool water, suggesting Mars once had significant liquid water on its surface. The research implies that Mars transitioned from a wet to a dry environment billions of years ago. Confirming these findings would require returning samples from Mars to Earth for comprehensive analysis. Join planetary scientist Beth Johnson for a chat with Dr. Bishop about the evidence for ferrihydrite and what it could have meant for life on Mars. (Recorded live 3 April 2025.)