Since January 2004, Mossbauer spectrometers 1] have been making measurements on Mars as a component of the Athena instrument suite because the technique can "yield information about early Martian environmental conditions" and can help in "identifying minerals formed in hot, watery environments that could preserve fossil evidence of Martian life" (from an early Athena web site; cf. 2]). The spectrometers are mounted on the instrument deployment armsoftwo Mars Exploration Rovers, MER-A (Spirit) and MER-B (Opportunity), where they have access to a wide range of rocks and soils. Initial...