Correction to ‘‘Chemical markers of possible hot spots on Mars’’

The rate coefficient, k, of the reaction is, however, the same as for R34 of WAE, i.e., k = 3.6 10 12 cm s . The above correction in R34 impacts the SO2 abundance and lifetime somewhat, as discussed below. [2] Once in the atmosphere, SO2 is photodissociated to produce SO, which is further photodissociated to form sulfur atoms. The reaction of SO with O2 or OH recycles sulfur atoms back to SO2 (R33, R35 in Table 2 of WAE). On the other hand, SO2 reacts with ozone (O3) to form sulfur trioxide (SO3, R34), which quickly combines with water vapor to form sulfuric acid (H2SO4, R39). H2SO4 undergoes condensation in the atmosphere. The revised reaction pathway is shown in Figure 1. [3] After applying the correction, for Model B in the original paper (WAE) where the assumed mixing ratio of the outgassed SO2 is 10 5 at the surface, the column abundance of SO2 above 10 km is found to be 3.8 10 molecules cm . The new abundance is 40% smaller compared with WAE because the additional loss of SO2 with O3 (R34) is now properly included. The abundance of SO3 and SO are also reduced but only slightly. The photochemical lifetime of SO2 is now 40 days, smaller than in WAE. Other species and their abundances, as well as the overall conclusions, are not affected. [4] For Model G of the original paper (WAE), where both SO2 and H2S are outgassed, each with a mixing ratio of 100 ppm at the surface, the resulting mixing ratios at 10 km are calculated to be 1.6 10 , 1.7 10 , and 1.9 10 , respectively, for SO2, H2S, and SO. The corresponding column abundances above 10 km are, in molecules cm , 1.5 10, 6.2 10, and 5.4 10. The maximum difference is in the SO2 abundance, with approximately 40% reduction compared to WAE. The number densities and mixing ratios of important sulfur species for this case are shown in Figure 2. For the case with current global upper limit of 0.1 ppm each for SO2 and H2S, the change due to above correction in R34 is imperceptible.