The Possible Aqueous Origins of Manganese Alteration Minerals in the Máaz Formation of Jezero Crater

Home to a lake around 4 billion years ago, Jezero crater is a unique location to study the interplay between igneous processes and aqueous alteration on ancient Mars. The Perseverance rover, which landed on Mars in 2021, can be used to study the history of the Jezero ancient lake system to better understand the duration of time liquid water was present on the surface of Mars. The Máaz formation, rich in basaltic rock, is the highest stratigraphic unit in the crater floor and hosts a diversity of alteration phases that indicate multiple aqueous episodes may have affected the crater floor rocks. Manganese alteration phases can give us insight into aqueous alteration since manganese is sensitive to changes in redox conditions and so variations in manganese concentrations in the crater can indicate shifts in redox levels in the ancient lake. The Curiosity rover in Gale crater and the Opportunity rover in Endeavor crater have also discovered manganese enrichments, which have been used to infer the presence of more highly oxidizing conditions on Mars over its history than previously thought. Manganese is typically a minor component in igneous minerals, with concentrations often below 1 wt% in most terrestrial rocks. Using data from the PIXL (Planetary Instrument for X-Ray Lithochemistry) instrument aboard the Perseverance rover, we investigated alteration products in the Máaz formation with anomalous MnO (much greater than 1 wt%). Our analysis reveals two anomalously high Mn regions in the Guillaumes and Alfalfa abrasion patches. The first has been identified as despujolsite (Ca₃Mn⁴⁺(SO₄)₂(OH)₆·3H₂O), discovered in the Guillaumes abrasion at a low stratigraphic unit within Máaz, which forms from either hydrothermal or lacustrine deposition in Earth analogs. In the Alfalfa abrasion patch, in a high stratigraphic unit in Máaz, we identified Mn-rich magnetite and a Mn-Fe hydrated sulfate in the solid solution series between szomolnokite (Fe²⁺SO₄·H₂O) and szmikite (MnSO₄·H₂O), suggesting a history of serpentinization followed by uplift and exposure to oxidizing acidic fluids. These findings underscore the complexity of aqueous alteration over the course of Jezero history. Future sample return missions could refine mineralogical interpretations and provide more information to refine our understanding of aqueous conditions and habitability in the crater.