Potential New Mineral Discovery on Mars Hints at Geothermal Activity
Valles Marineris, Mars – Scientists have identified an unusual iron sulfate on Mars that may represent a previously unknown mineral, potentially rewriting our understanding of the planet’s geologic history. The discovery, detailed in a new study published in Nature Communications, centers around a mineral dubbed ferric hydroxysulfate, found within ancient sulfate deposits near the massive Valles Marineris canyon system.
The research, led by Dr. Janice Bishop of the SETI Institute and NASA’s Ames Research Center, combined laboratory experiments with orbital data analysis. Sulfur is abundant on Mars, frequently combining with other elements to form sulfate minerals. Unlike Earth, where sulfates typically dissolve in rainwater, Mars’ extremely dry conditions allow these minerals to persist for billions of years, preserving clues about the planet’s past environments.
For nearly two decades, researchers have been puzzled by unusual spectral signals emanating from layered iron sulfates on Mars. The new investigation focused on two key areas near Valles Marineris: Aram Chaos, where ancient water once flowed, and the plateau above Juventae Chasma, a deep canyon.
Scientists discovered that heating polyhydrated sulfates to 50°C converts them into monohydrated forms, and exceeding 100°C results in the formation of ferric hydroxysulfate. This suggests that geothermal heat likely altered the minerals after their initial deposition. Ferric hydroxysulfate is rarer than other sulfates in the region, leading scientists to believe warmer geothermal sources may have once existed beneath the surface.
Laboratory experiments conducted at the SETI Institute and NASA Ames traced the mineral’s evolution, beginning with rozenite and transforming through szomolnokite to ultimately form ferric hydroxysulfate. This process requires oxygen and generates water.
“Our experiments suggest that this ferric hydroxysulfate only forms when hydrated ferrous sulfates are heated in the presence of oxygen,” explained Dr. Johannes Meusburger, a postdoctoral researcher at NASA Ames. The resulting change in the mineral’s structure drastically alters how it absorbs infrared light, enabling its identification using the CRISM instrument aboard orbiting spacecraft.
While the mineral’s crystal structure is similar to szomolnokite, it appears to form more readily from rozenite. The formation of ferric hydroxysulfate requires temperatures exceeding 100°C, significantly warmer than typical Martian surface conditions, indicating a more recent origin during the Amazonian period.
To officially recognize the material as a new mineral, scientists must also locate it on Earth. But, this discovery provides valuable insight into the roles of heat, water, and chemical reactions in shaping the Martian landscape and the planet’s potential for past habitability.