Atmosphere of Mercury Atmosphere of Mercury Mercury has a very tenuous and highly variable atmosphere (surface-bound exosphere) containing hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor, with a combined pressure level of about 10 bar (1 nPa). The exospheric species originate either from the Solar wind or from the planetary crust. Solar light pushes the atmospheric gases away from the Sun, creating a comet-like tail behind the planet. The existence of a Mercurian atmosphere had been contentious before 1974, although by that time a consensus had formed that Mercury, like the Moon, lacked any substantial atmosphere. This conclusion was confirmed in 1974
Atmosphere of Venus volcanoes as well as lightning. The Venus In-Situ Explorer, proposed by NASA's New Frontiers program is a proposed probe which would aid in understanding the processes on the planet that led to climate change, as well as paving the way towards a later sample return mission. A craft called the Venus Mobile Explorer has been proposed by the Venus Exploration Analysis Group (VEXAG) to study the composition and isotopic measurements of the surface and the atmosphere, for about 90 days. The mission has not been selected for launch. After missions discovered the reality of the harsh nature of the planet's