The mesosphere protects Earth by preventing meteor impacts. When objects from space enter the atmosphere, the mesosphere is the first dense region of gas they encounter. Most of these objects vaporize or melt when they collide with atmospheric gas particles.
The mesosphere is one of the least-studied parts of Earth's atmosphere. This is because it lies above the maximum altitude for aircraft or weather balloons, but below the minimum altitude for a spacecraft to maintain orbit. The only way to study the mesosphere is with non-orbital rocket flights called sounding rockets.
The mesosphere begins approximately 31 miles above Earth's surface and ends approximately 62 miles above Earth. Its upper boundary is called the mesopause, and is the coldest naturally-occurring location on Earth. These temperatures reach a low of minus 226 degrees Fahrenheit.
The lower levels of the mesosphere are home to unique weather phenomena. Noctilucent clouds are the highest-altitude clouds in Earth's atmosphere, and most often form around the North and South Poles. A form of lightning called a sprite forms in the mesosphere, many miles above thunder clouds. The mesosphere also has a higher concentration of iron and other metal molecules than the rest of the atmosphere; this is due to the many meteors that vaporize there.