Atmosphere of Mercury

Mercury has a very weak atmosphere. Its atmosphere contains hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor. It has a combined pressure level of about 10−14 bar (1 nPa). The elements may come from either the solar wind or from the planetary crust.
Composition.
Mercury's atmosphere consists of different types of elements. These elements may come from the solar wind or from the planetary crust. The first elements discovered were atomic hydrogen, helium and atomic oxygen. They were observed by the ultraviolet radiation photometer of "Mariner 10" in 1974. The hydrogen and helium in Mercury's atmosphere are believed to come from the solar wind. Oxygen is believed to come from Mercury's crust.
The fourth element that was discovered in Mercury's exosphere was sodium. It was discovered in 1985 by Drew Potter and Tom Morgan. The fifth element that was discovered in Mercury's exosphere was potassium. It was discovered in 1986 by Drew Potter and Tom Morgan. In 1998, calcium was found in Mercury's atmosphere. Magnesium was discovered by "MESSENGER".