Direct comparisons of the datasets from Fig. 6. Panel a: monthly averages of the gas production rate Q (derived from NG data) plotted against the monthly NG detection rate multiplied by the square of the average cometocentric distance. The Pearson correlation coefficient is 0.86. Panel b: monthly averages of the water production rate (Hansen et al. 2016) versus the monthly NG detection rate multiplied by the square of the average cometocentric distance. The Pearson correlation coefficient between the two quantities is 0.98. Panel c: monthly average of the ground-based measurements of the brightness of 67P (Snodgrass et al. 2016) versus the monthly NG detection rate multiplied by the square of the average cometocentric distance. The Pearson correlation coefficient is −0.73.