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 measurements at the Spirit site showed that surface samples contained primarily basaltic minerals with weathering by physical processes [3], while mineralogy inferred from data acquired at the Opportunity site provided evidence for past aqueous processes [4]. More recently, Mossbauer spectroscopy has identified goethite at Columbia Hills [5] and contributed to an understanding of the nature of Martian atmospheric dust and its implications for the history of water on Mars [6]. It is important that MER-team results be verified and expanded upon. Since August 2004, Mars Mossbauer and related data, with supporting documentation, have been made available to the science community via the Planetary Data System (PDS) at the MER Analyst's Notebook download site (http://www. anserverl. eprsl. wustl. edu/) and at the PDS Geosciences Node (http://www. pds-geosciences. wustl. edu/).