THE DEEP ATMOSPHERE OF VENUS

Venus as a planet resembles the Earth, but has a much hotter and dense r atmosphere due to an extreme case of the greenhouse effect, caused b y compositional differences and tile thick cloud cover. Studies of the lower atmosphere are inhibited by the cloud opacity, which makes remo te measurements at most frequencies short. of the radio range quite di fficult. Progress in understanding of the com position and thermal str ucture below the clouds has been made by the Pioneer and Venera entry probes of the 1970s, and more recently with results from the Galileo f ly-by in 1990. The latter exploited the newly discovered near-infrared 'windows' to achieve measurements of carbon monoxide and water vapour abundances in the deep atmosphere, and provided the first detailed vi ew of the global cloud structure. The morphology and spatial variation s seen in the main mass of clouds are remarkable, and suggest a powerf ul and diverse meteorology dominated by convection. Carbon monoxide is significantly more abundant at high northern latitudes than at low la titudes in either hemisphere.