Evidence for Antarctic alteration of Martian meteorite

The magnetites and sulfides located in the rims of carbonate globules in the Martian mete-orite ALH84001 have been claimed as evidence of past life on Mars. The globules ’ chemical zonation patterns suggest that the rims may be a product of weathering processes. A kinetic model was used to examine the possibility that these rims formed through the dissolution and reprecipitation of a primary Martian carbonate while the meteorite was exposed at the surface in Antarctica. The results suggest that the formation of the rims under such conditions would take less than fifty years, and that sufficient time was therefore available for the rims to form in Antarctica. If this model is correct, then any biogenic features in the rims are most likely the products of terrestrial, rather than Martian, life.