Unique Martian sulfate points to recent thermal activity and mineral formation

Unique Martian sulfate points to recent thermal activity and mineral formation
by Clarence Oxford
Los Angeles CA (SPX) Aug 06, 2025

New research led by the SETI Institute has identified an unusual iron sulfate on Mars that may represent a previously unknown mineral, offering new insights into the planet's thermal and geochemical history. The study, published in Nature Communications, reveals the presence of ferric hydroxysulfate, a mineral that likely formed through heating and oxidation of more common hydrated sulfates.

The team, headed by Dr. Janice Bishop, combined laboratory simulations with Mars orbiter data to identify this rare phase of sulfate in two regions near the vast Valles Marineris canyon system: Aram Chaos and the plateau above Juventae Chasma. These areas contain sulfates with distinct spectral signatures, previously unclassified, which now appear linked to recent heat-driven transformations.

In Juventae Plateau, ferric hydroxysulfate occurs in thin, meter-scale layers sandwiched between basaltic materials. Researchers suggest these layers were altered by thermal energy from volcanic sources such as lava or ash. "Investigation of the morphologies and stratigraphies of these four compositional units allowed us to determine the age and formation relationships among the different units," explained Dr. Catherine Weitz, co-author and Senior Scientist at the Planetary Science Institute.

Aram Chaos, a rugged terrain shaped by ancient floods, also contains layered sulfates. The upper layers consist of polyhydrated sulfates, while the lower ones transition into monohydrated and ferric hydroxysulfate phases. These changes align with lab results showing that heating polyhydrated forms above 50 C creates monohydrated sulfates, and above 100 C yields ferric hydroxysulfate.

Mars orbiter data, specifically from the CRISM instrument, allowed the team to match these transformations to observed spectral data. "Our experiments suggest that this ferric hydroxysulfate only forms when hydrated ferrous sulfates are heated in the presence of oxygen," said Dr. Johannes Meusburger of NASA Ames. "While the changes in the atomic structure are very small, this reaction drastically alters the way these minerals absorb infrared light."

Equation 1 summarizes the transformation: 4 Fe2+SO4-H2O + O2 - 4 Fe3+SO4OH + 2 H2O

This reaction, requiring both heat and oxygen, likely occurred in localized geothermal environments - conditions more active and recent than previously assumed. While structurally similar to known sulfates like szomolnokite, the newly identified ferric hydroxysulfate appears more thermally stable and may qualify as a new mineral. However, as Dr. Bishop noted, "Scientists must also find it on Earth to officially recognize it as a new mineral."

The findings suggest that Mars has experienced recent chemical and thermal processes, particularly during the Amazonian period, less than 3 billion years ago. This evidence of recent mineral transformation deepens our understanding of Mars's evolving surface and its capacity to support habitable conditions.

Research Report:Characterization of ferric hydroxysulfate onMars and implications of the geochemicalenvironment supporting its formation