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Comparison of H2SO4 and SO2 Abundances in the Venus Atmosphere Derived from Previous Radio Occultation Studies

Presentation #406.04 in the session Venus (Poster)

Published onOct 23, 2023
Comparison of H2SO4 and SO2 Abundances in the Venus Atmosphere Derived from Previous Radio Occultation Studies

Venus is an enigmatic world shrouded in a thick atmosphere composed predominantly of carbon dioxide. Within this complex atmospheric environment, sulfuric acid vapor forms a ca. 20 km thick cloud deck located between about 50 and 70 km altitude. Due to the increasing temperature at lower altitudes, H2SO4 evaporates and forms a haze layer extending to about 35 km. The latter is a strong absorber of radio waves as was observed in radio occultation measurements.

Radio occultation, a powerful remote sensing technique, has been employed to probe the vertical structure and composition of Venus’ atmosphere since the 1960s. By measuring the bending and attenuation of radio waves as they pass through the planet’s atmosphere, radio occultation allows to derive valuable information about temperature, pressure, density, and amount of sulfuric acid vapor and sulfur dioxide.

First measurements of the H2SO4(g) mixing ratio using the radio occultation technique were carried out in 1967 with the Mariner V spacecraft. Two measurements were performed at the equatorial day side and nightside. Later, the Mariner 10 flyby on Venus in 1974 was used to conduct one radio occultation measurement at the equatorial region. In the years 1983/1984, the Venera 15/16 spacecrafts have provided attenuation profiles derived from radio signals at 5 cm wavelength. The first extended study covering a wide range of latitudes was performed with the Pioneer Venus mission between the years 1978 and 1992. In the early 1990s, sulfuric acid vapor profiles were derived simultaneously from X- and S-Band radio signals of the Magellan spacecraft. Similar to PVO, Venus Express has provided the H2SO4(g) mixing ratio from different latitudes and local times between the years 2006 and 2014.

We present, compare, and discuss the H2SO4(g) profiles calculated from the previous radio occultation measurements. For this purpose, the Mariner V RO measurements were translated into H2SO4(g) profiles using the published temperature, pressure, and attenuation profiles. The atmospheric profiles derived from the PVO mission were recalculated on the basis of improved orbit data. Based on a model atmosphere, we additionally present the degree of attenuation expected for the future EnVision RO measurements.

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