The Tellus airborne geophysical data sets provide impetus to many new lines of research. The radiometric data, conventionally used for bedrock investigations, have recently been used to support regional mapping of peat extent and thickness, and thus contribute to refining our estimates of the soil carbon inventory. By extending the theory to include density and water saturation we can also begin tentatively to apply these radiometric data to mapping changes in these diagnostic soil characteristics. Here the complete Tellus data set is revisited and examples shown of how radiometric signatures vary over different soil types.