Composition of Venusian Atmosphere
The atmospheres of Venus and Mars are similar in the fact that they are both mainly composed of carbon dioxide (CO2); However their atmospheres have very different situations while the atmosphere of Mars is very dilute in comparison to the atmosphere of earth, Venusian atmosphere is very dense when compared to Earth atmosphere. Mass and pressure of Venusian atmosphere are about 90 times greater than those of Earth atmosphere.
The dense concentration of carbon dioxide in the Venusian atmosphere results in a very strong greenhouse effect causing the surface temperature of Venus to rise very high (more than 700 K) and surpass that of the Mercury, the closest planet to the Sun in the solar system.
Another important feature of Venusian atmosphere is thick clouds mainly composed of sulfuric acid formed through chemical reactions from sulfur dioxide and water present in the atmosphere. Such thick clouds prevent visual observation of the Venusian surface beside they reflect and scatter most of the sunlight.