Table 2 Best-estimate bulk abundances of noble gases in comet 67P/C-G in the second column.

The third column gives the correction factor applied to the values from the second column in table S3 based on the expected outgassing velocities. We assume that, close to perihelion, N2 and H2O share the same velocity due to collisional coupling and apply no correction. Hence, for the May 2016 period, the reference mass for the 1/m velocity correction becomes that of molecular nitrogen (m1 = 28 u) instead of water (18 u). Errors reflect 1-σ SEM and calibration uncertainties.

SpeciesProduction rate ratio of 67P/C-Gm2/m1Conditions/notes
N2/H2O(8.9 ± 2.4) × 10−4(1.000)Collisional, measured near perihelion
36Ar/N2(5.5 ± 1.5) × 10−30.882Rarefied, measured beyond 3 AU
36A/H2O(4.9 ± 1.9) × 10−60.882Combination of rarefied and collisional
Ar/H2O(5.8 ± 2.2) × 10−60.882∙(1.000)Combination of rarefied and collisional
Kr/H2O(4.9 ± 2.2) × 10−70.577Combination of rarefied and collisional
Xe/H2O(2.4 ± 1.1) × 10−70.461Combination of rarefied and collisional
Ne/H2O<5 × 10−81.128Upper limit