Pioneer Venus gas chromatography of the lower atmosphere of Venus

Abstract

A gas Chromatograph mounted in the Pioneer Venus sounder probe measured the chemical composition of the atmosphere of Venus at three altitudes. Ne, N2, O2, Ar, CO, H2O, SO2, and CO2 were measured, and upper limits set for H2, COS, H2S, CH4, Kr, N2O, C2H4, C2H6, and C3H8. Simulation studies have provided indirect evidence for sulfuric acid‐like droplets and support the possibility of water vapor at altitudes of 42 and 24 km. The paper discusses the implications of these results for the origin, evolution, and present state of Venus' atmosphere.

Venus Atmospheric Thermal Structure and Radiative Balance

“…At that time, no explanation for the variation in the nitrogen abundance was available (von Zahn et al 1983) as the impact of the supercritical state of the two primary constituents was not appreciated and considered regarding these results. This gradient was noted by others (von Zahn et al 1983) but for lack of a plausible explanation even though the measurements were the most accurate ever obtained, the result was ignored and only an average value was provided in the VIRA model, with an error estimate of 0.8% equal to the standard deviation of the three measurements which is much larger than the accuracy of the nitrogen measurements (< 0.02%, Oyama et al 1980). It is interesting to note that at the same altitudes, CO 2 abundances were correspondingly lower (Fig.…”

“…The experimental values obtained by Oyama et al (1980) however show that the abundance of N 2 (measured with an accuracy of 0.01%) decreased by about 1.4% between 52 and 22 km altitude at the Pioneer Venus Large Probe location. At that time, no explanation for the variation in the nitrogen abundance was available (von Zahn et al 1983) as the impact of the supercritical state of the two primary constituents was not appreciated and considered regarding these results.…”

“…Thus it has been known that under the temperature and pressure conditions near the surface of Venus, both the primary constituents should be in supercritical state. Yet, surprisingly little attention has been paid to the effects of the mixture of two supercritical fluid states of the primary constituents in the lower atmosphere of Venus, and to the observation that a vertical gradient in the abundance of nitrogen was measured by the Pioneer Venus Large Probe GCMS (Oyama et al 1980) which could not be explained. Recent laboratory experimental data suggest that homogenous mixtures of supercritical carbon dioxide and nitrogen tend to separate vertically when left alone (Hendry et al 2013).…”

“…Fig. 39 Altitude profiles of CO 2 and N 2 volume mixing ratios measured by Oyama et al (1980) and inferred by Peplowski and Lawrence (2016). The dotted curve shows a linear fit to the nitrogen abundances measured at 64, 52, 41 and 22 km.…”

“…Additionally, experimental and theoretical investigations of mixtures of super critical gases are encouraging some earlier puzzling observational results such as the unexplained vertical gradient of nitrogen abundance in the atmosphere (Oyama et al 1980) and the presence of a puzzling unstable layer below 7 km altitude seen in the VeGa 2 lander data (Lebonnois and Schubert 2017) to be revisited. The LIR camera on Akatsuki orbiter ) is providing continuous cloud top brightness temperatures and raising more questions.…”