There is an urgent need in the ocean science community for accurate, unambiguous measurements of iron(II) (Fe(II)) in the marine water column. Without these data it is impossible to obtain a complete understanding of the iron cycle and its biological implications. While the luminol chemiluminescence method and existing data obtained from oxygen minimum zones are probably robust, this method may overestimate Fe(II) in the euphotic zone. Moffett proposes here take on the challenge of producing...