there are no moons in our solar system that have an atmosphere similar to Earth's. Earth's atmosphere is primarily composed of nitrogen (78%) and oxygen (21%), along with trace amounts of other gases, and it provides a breathable environment for life as we know it.
However, there are a few moons in the outer solar system that have atmospheres, although they are quite different from Earth's.
Titan (moon of Saturn): Titan is known to have a dense atmosphere primarily composed of nitrogen, with small amounts of methane and other hydrocarbons. It is the only moon in our solar system with a substantial atmosphere. The conditions on Titan, with its thick atmosphere and organic chemistry, make it one of the most Earth-like environments in our solar system, although it is not suitable for human life due to the extreme cold and lack of oxygen.
Triton (moon of Neptune): Triton has a thin atmosphere that contains nitrogen, methane, and trace amounts of other gases. It is believed to have an active atmosphere with geysers erupting from its surface.
Enceladus (moon of Saturn): Enceladus has a very thin atmosphere composed mostly of water vapor, with some other gases present. It is known for its geysers of water erupting from its icy surface, suggesting the presence of subsurface liquid water and potential habitable conditions.
It's important to note that our understanding of the solar system is constantly evolving, and future discoveries may reveal more moons with atmospheres or even environments that could potentially support life.