The availability of vast quantities of data through electronic archives has transformed astronomi-cal research. It has also enabled the creation of new products, models and simulations, often from distributed input data and models, that are themselves made electronically available. These prod-ucts will only provide maximal long-term value to astronomers when accompanied by records of their provenance; that is, records of the data and processes used in the creation of such prod-ucts. We use the creation of image mosaics with the Montage grid-enabled mosaic engine to emphasize the necessity of provenance management and to understand the science requirements that higher-level products impose on provenance management technologies. We describe e...