Magnetic properties experiments on the Mars Pathfinder lander: Preliminary results

Many of the particles currently suspended in the martian atmosphere are magnetic, with an average saturation magnetization of about 4 A-m²/kg (amperes times square meters per kilogram). The particles appear to consist of claylike aggregates stained or cemented with ferric oxide (Fe₂O₃); at least some of the stain and cement is probably maghemite (γ-Fe₂O₃). The presence of the 'y phase would imply that Fe²⁺ ions leached from the bedrock, passing through a state as free Fe²⁺ ions dissolved in liquid water. These particles could be a freeze-dried precipitate from ground water poured out on the surface. An alternative is that the magnetic particles are titanomagnetite occurring in palagonite and inherited directly from a basaltic precursor.