CNES – EHVAV

The objective of the project is to provide experimental constraints on potential elemental and/or isotopic fractionation induced by high speed sampling of the Venus atmosphere. This project is part of the development of the VATMOS-SR (Venus atmospheric sample return) space mission concept that has been submitted to ESA in early 2022. The space probe of the VATMOS-SR project would dive into the atmosphere of Venus and sample its atmosphere at about 110 km altitude. The measurement of the elemental and isotopic composition of rare gases and stable isotopes of the Venus atmosphere would allow to bring constraints on the origin of the Venus atmosphere, on its evolution over time but also on the geological history of the planet, in particular thanks to the measurement of radiogenic isotopes produced inside Venus and degassed over time in its atmosphere (Avice et al., 2022). The orbital parameters of the probe (which must then return to Earth) imply that the sampling will take place at a speed between 10 and 13 km.s-1. Once inside the probe, the sampled gas will have to circulate through a series of ducts but also through valves that will be used to close the sampling cylinders to preserve the gas for measurement after the return to Earth of the probe. Numerical simulations have shown that the valves used have a significant impact on the gas velocity and are therefore likely to induce elemental and/or isotopic fractionation. The scientific objective of this project is therefore to measure the fractionation induced by these valves by reproducing, in the laboratory, the pressure differential of a gas of known composition that will flow through a miniaturized valve and that will be sampled in sealed tanks. The gas sampled during this analogous experiment will then be measured on the rare gas measurement platform of the Institut de physique du globe de Paris.