Atmosphere of Venus
In 1761, Russian polymath Mikhail Lomonosov observed an arc of light surrounding the part of Venus off the Sun's disc at the beginning of the egress phase of the transit and concluded that Venus has an atmosphere. In 1940, Rupert Wildt calculated that the amount of CO in the Venusian atmosphere would raise surface temperature above the boiling point for water. This was confirmed when Mariner 2 made radiometer measurements of the temperature in 1962. In 1967, Venera 4 confirmed that the atmosphere consisted primarily of carbon dioxide.
Maat Mons
Intriguingly for planetary geologists, atmospheric studies carried out by the Pioneer Venus probes in the early 1980s revealed a considerable variation in the concentrations of sulfur dioxide (SO) and methane (CH) in Venus' middle and upper atmosphere. One possible explanation for this was the injection of volcanic gases into the atmosphere by plinian eruptions at Maat Mons.