The magnetic properties experiments on Mars Pathfinder

The Mars Pathfinder lander carried two magnet arrays, each containing five small permanent magnets of varying strength. The magnet arrays were passive ly exposed to the wind borne dust on Mars. By the end of the Mars Pathfinde r mission a bull's-eye pattern was visible on the four strongest magnets of the arrays showing the presence of magnetic dust particles. From the image s we conclude that the dust suspended in the atmosphere is not solely singl e phase particles of hematite (alpha-Fe2O3) and that single phase particles of the ferrimagnetic minerals maghemite (gamma-Fe2O3) or magnetite (Fe3O4) are not present as free particles in any appreciable amount. The material on the strongest magnets seems to be indistinguishable from the bright surf ace material around the lander. From X-ray fluorescence it is known that th e soil consists mainly of silicates. The element iron constitutes about 13% of the soil. The particles in the airborne dust seem to be composite, cont aining a few percent of a strongly magnetic component. We conclude that the magnetic phase present in the airborne dust particles is most likely maghe mite. The particles thus appear to consist of silicate aggregates stained o r cemented by ferric oxides, some of the stain and cement being maghemite. These results imply that Fe2+ ions were leached from the bedrock, and after passing through a state as free Fe2+ ions in liquid water, the Fe2+ was ox idized to Fe3+ and then precipitated. It cannot, however, be ruled out that the magnetic particles are titanomagnetite (or titanomaghemite) occurring in palagonite, having been inherited directly from the bedrock.