Hviid S F, Madsen M B, Gunnlaugsson H P, Goetz W, Knudsen J M, Hargraves R B, Smith P, Britt D, Dinesen A R, Mogensen C T, Olsen M, Pedersen C T, Vistisen L
Oersted Laboratory, Niels Bohr Institute for Astronomy, Physics, and Geophysics, University of Copenhagen, Copenhagen, Denmark.
Science. 1997 Dec 5;278(5344):1768-70. doi: 10.1126/science.278.5344.1768.
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 (gamma-Fe2O3). The presence of the gamma 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.
