Shock Demagnetization of Pyrrhotite (Fe_1−xS, x⩽0.13) and Implications for the Martian Crust and Meteorites

After cessation of the dynamo on Mars, giant impact events should have demagnetized large regions of the crust. Models of the decay of shock pressure with distance indicate that the demagnetized zones are bound by peak shock pressures between 1 and 3 GPa. We performed the first planar shock recovery experiments at these pressures on natural pyrrhotite, a magnetic mineral found in Martian meteorites. Post‐shock magnetic measurements show that pyrrhotite demagnetizes significantly (∼85–90%) when subject to shock pressures between 1 and 4 GPa. Permanent changes to the magnetic properties of recovered samples include an increase in the saturation remanence and the mean destructive field, indicating that shocks harden the coercivity. We conclude that pyrrhotite is a candidate carrier for the magnetization in the Martian crust and that pyrrhotite in meteorites shocked to modest pressures may retain a pre‐shock remanence.