HCl was observed for the first time in the Venus atmosphere by Connes et al. [Connes et al., 1967], who estimated its mixing ratio at the cloud top as being 0.6 ppm (refined to 0.4±0.07 ppm by [Young, 1972]). More recent nightside observations [Bézard et al., 1990] provided measurements of HCl below the clouds. These authors reported values of 0.5±0.15 ppm, which are similar to the values found by Connes et al. (1967). Recently, Iwagami et al. [Iwagami et al., 2008] measured hemispheric distributions of HCl mixing ratio above and below the Venus ‘ cloud deck. These authors reported mean values of 0.76±0.1 ppm at altitudes between 61-67 km and 0.4±0.05 ppm at about 20 km. They argued that the larger HCl mixing ratio found above the clouds than that existing below the cloud requires the presence of a production process of HCl in the cloud region or above.

Isotopologues H35Cl and H37Cl

MATLAB Handle Graphics

Vertical profiles of the HCl density (left) and volume mixing ratio in ppm (right) obtained during the three occultations 341 ( ---: 28/03/2007; distance to the limb at 65 km tangent height: 3346 km; 82 N), 356 ( … : 12/04/2007; distance to the limb: 3298 km; 84 N), and 366 ( - - - : 22/04/2007; distance to the limb: 3898 km; 73 N). For comparison, the solid line with dots corresponds to a profile of constant vmr (0.5 ppm). The vmr in this plot correspond to the ratios of the HCl densities to the total air densities obtained from the temperatures and pressures of the VENUS model. Error bars correspond to the fitting error on the single fitted parameter, i.e. the density in the corresponding layer, and does not take into account the errors on the densities in the upper layers. (credit: BISA)

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Relevant Publications

A warm layer in Venus’ cryosphere and high-altitude measurements of HF, HCl, H2O and HDO (pdf - 384 KB)
Composition of the Venus mesosphere sosphere measured by SOIR on board Venus Express (pdf - 743 KB)
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