Detection of ferrihydrite in Martian red dust records ancient cold and wet conditions on Mars.

Iron oxide-hydroxide minerals in Martian dust provide crucial insights into Mars' past climate and habitability. Previous studies attributed Mars' red color to anhydrous hematite formed through recent weathering. Here, we show that poorly crystalline ferrihydrite (FeOH · nHO) is the dominant iron oxide-bearing phase in Martian dust, based on combined analyses of orbital, in-situ, and laboratory visible near-infrared spectra.

Active Mars: A Dynamic World.

Mars exhibits diverse surface changes at all latitudes and all seasons. Active processes include impact cratering, aeolian sand and dust transport, a variety of slope processes, changes in polar ices, and diverse effects of seasonal CO frost. The extent of surface change has been surprising and indicates that the present climate is capable of reshaping the surface.