Assessing the Role of Water–Rock Interactions in Martian Crustal Magnetization

Mars exhibits strongly magnetized crust, interpreted as a remanent signature acquired during the operation of the ancient martian dynamo. Several mechanisms can produce crustal magnetization, including thermal, shock, and chemical remanent processes. Thermal remanent magnetization can produce relatively clear and coherent signatures, shock-related magnetization associated with impact craters often yields more ambiguous or spatially complex magnetic patterns.Chemical remanent magnetization (CRM) can be acquired when water interacts with specific rock types, particularly olivine-rich lithologies, leading to the formation of secondary magnetic minerals such as magnetite. Geological and mineralogical evidence for past water activity on Mars, together with the widespread presence of suitable precursor minerals, suggests that this process may have been an important contributor to the martian crustal magnetic field.

Here, we evaluate magnetic field signatures in regions where water was likely present, at or beneath the surface. In areas where hydrothermal circulation is thought to have been active, such as impact-related hydrothermal systems, we identify magnetization signatures in regions that were active early in Mars’ history, including areas surrounding Ladon crater. In contrast, other regions such as Eridania basin, exhibit distinct demagnetization signatures, which may indicate that hydrothermal circulation persisted beyond the cessation of the martian dynamo. By further comparing magnetic anomalies with morphological indicators of aqueous alteration on the surface, we assess whether chemical remanent magnetization associated with water–rock interactions can explain observed crustal magnetic signatures and contribute significantly to the magnetization of the martian crust.