Superadiabatic Atmospheric Layer on Venus, as inferred from the Venera-4 Probe Measurements

Abstract

THE USSR Venera-4 probe entered the atmosphere of Venus on October 18, 1967, made the first direct measurements of the physico-chemical characteristics of the lower atmosphere and landed smoothly on the planet's surface^1,2. The probe's whole descent took place on the night side of the planet, close to the equator and about 1,500 km from the terminator. The probe contained two resistance thermometers, an anaeroid barometer transducer, a densitometer and eleven core gas analysers. Immediately after the probe's parachutes opened at an altitude of 26 km, an atmospheric sample was inserted in five cores. The remaining six cores received samples at an altitude of 23 km. All the analysers operated. The carbon dioxide content turned out to be 90 per cent, with less than 10 per cent error. The water or moisture content turned out to be greater than 0.1 per cent and less than 0.7 per cent. In one analyser the oxygen content was greater than 0.4 per cent. In another analyser the oxygen and water content were less than 1.5 per cent, that is, the oxygen content is somewhere between 0.4–1.4 per cent. Finally, the nitrogen content is less than 7 per cent, for an analyser with this response showed no presence of nitrogen. Table 1, derived from these measurements, presents five atmospheres of differing composition for Venus, depending on the relative amounts of carbon dioxide, between the possible limits 80–99.5 per cent. Probably small quantities of argon and other inert gases are present in the atmosphere of Venus as may be deduced from the composition.