Mercury has almost no atmosphere. The planet was very hot when it formed. Also, it is very near the Sun. The intense heat caused almost all its gases to burn up. Floating above the surface is a tiny amount of sodium and potassium. There are also traces of oxygen, hydrogen, and helium. These gases may be released from rocks on the surface. They may be gases left by the solar wind.
From Earth, Mercury doesn't appear nearly as bright as Venus. One reason is that it's smaller and farther from the Earth than Venus. Another reason is that Mercury's albedo is only 0.1. Mercury has no clouds to reflect light. So, most of
