Mars Exploration Rover PDS4 Documentation Bundle This bundle contains primary members for Mars Exploration Rover (MER) documents formatted for PDS4. Each document in this bundle is described by a PDS4 label in a separate file with the same name as the document but with the extension XML. PDS4 labels are XML (eXtended Markup Language) files that conform to the PDS4 Information Model XML schema at https://pds.nasa.gov/pds4/schema/released/. The PDS4 labels are best viewed in an XML- aware text editor, and may be used by software that can manipulate XML documents. The MER documentation bundle has one collection organized into several subdirectories. There is one subdirectory for each MER instrument along with a subdirectory for documents that apply across instruments. Within the instrument subdirectories there are documents that pertain to that instrument on both rovers. This bundle was created and archived by the Geosciences Node of the Planetary Data System. Questions about this bundle may be directed to geosci@wunder.wustl.edu.