The Clouds of Venus – an overview of Venus Express results

International audienceVenus is completely enveloped by clouds. The main cloud layers stretch from altitudes of 48 – 75 km, with additional tenuous hazes found at altitudes 30 – 100 km. Clouds play a crucial role in governing atmospheric circulation, chemistry and climate on all planets, but particularly so on Venus due to the optical thickness of the atmosphere. The European Space Agency’s Venus Express (VEx) satellite has carried out a wealth of observations of Venus clouds since its arrival at Venus in April 2006. Many VEx observations are relevant to cloud science – from imagers and spectrometers to solar, stellar and radio occultation – each covering different altitude ranges, spectral ranges and atmospheric constituents.We have formed an International Team at the International Space Science Institute to bring together scientists from each of the relevant Venus Express investigation teams as well as from previous missions, as well as those developing computational and analytical models of clouds and hazes. The aims of the project are (1) to perform intercomparisons of cloud parameters measured using different techniques, (1) to create self-consistent reference cloud/haze models which capture not only a mean cloud structure but also its main modes of variability; and (2) to bring together modelers and observers, to reach an understanding of clouds and hazes on Venus which matches all observables and is physically consistent.This talk will present an overview of Venus Express cloud observations of all different types, and discuss progress towards a new reference cloud model to be submitted to an update of the Venus International Reference Atmosphere

The 2010 European Venus Explorer (EVE) mission proposal

International audienceThe European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an 'M-class' mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55 km, where temperatures and pressures are benign (∼25°C and ∼0.5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet. This offers an ideal platform for the two main science goals of the mission: study of the current climate through detailed characterization of cloud-level atmosphere, and investigation of the formation and evolution of Venus, through careful measurement of noble gas isotopic abundances. These investigations would provide key data for comparative planetology of terrestrial planets in our solar system and beyond