During its visit to Mercury, Mariner 10 detected a tiny amount of helium 1000-km above the surface as well as traces of sodium, potassium and oxygen. Aside from these elements, Mercury has almost no atmosphere due to an interaction between the planet's magnetic field and the Sun. Combined with the Sun's solar wind and Mercury's extremely high temperatures, atoms of the atmosphere are constantly blasted into space. However, it is also constantly replenished by the capturing of solar wind particles and radioactive decay of Mercury's crust.
The planet's temperature can range from a bitter -300 degrees to a searing 800 degrees Fahrenheit (hot enough for lead to melt). The large range of surface temperature is due to two factors: the thin atmosphere and extreme close range to the Sun. Because almost no atmosphere exists on Mercury, it is not possible to regulate temperature. In addition, a Mercury year is only 88 Earth days long, with summer lasting around 60 days and the rest of the season's 30 days.
The Thin Atmosphere on Mercury 
