The exosphere is a layer of the Earth's atmosphere that is primarily made up of thin gas particles and extends far beyond the planet's surface. It is also known as the outermost layer of the Earth's atmosphere. There are several synonyms that can be used to refer to the exosphere such as outer space, vacuum, atmospheric limit, and thermosphere. The exosphere is further divided into the ionosphere and the magnetosphere. While the ionosphere is responsible for reflecting radio waves back to Earth and the magnetosphere shields the planet from harmful solar radiation. The exosphere is an important part of the Earth's protective barrier and plays a critical role in preserving life on the planet.