The mesosphere is a layer of Earth’s atmosphere above the stratosphere and beneath the thermosphere, extending from approximately 50 to 85 kilometers (31 to 53 miles) above the planet’s surface. This region acts as a transitional area between the lower atmosphere and space. It contributes to Earth’s defense against space debris and offers unique conditions for atmospheric research.
A Natural Shield Against Space Debris
The mesosphere acts as a natural shield, protecting Earth from incoming meteors and space debris. Most objects burn up within this layer, preventing impacts on the planet’s surface. As meteoroids enter the mesosphere, they encounter increasing air density.
Friction from high-speed entry against atmospheric gases creates intense heat. This heating causes meteoroids to incinerate and disintegrate into small dust particles before reaching the ground. This is why people observe “shooting stars,” which are meteors burning up in the mesosphere. Estimates suggest about 40 tons of meteors enter Earth’s atmosphere daily.
Unlocking Atmospheric Secrets in the Mesosphere
The mesosphere has unique characteristics, making it important for scientific investigation. It is the coldest layer of Earth’s atmosphere, with temperatures decreasing with height to approximately -90°C (-130°F) near its top, the mesopause. These low temperatures result from decreasing absorption of solar radiation at higher altitudes.
Within this frigid environment, rare phenomena such as noctilucent clouds, also called polar mesospheric clouds, can form. These are the highest clouds in Earth’s atmosphere, appearing as wispy, silvery-blue structures visible in deep twilight during summer months at high latitudes. Noctilucent clouds are composed of tiny ice crystals that form around fine dust particles, potentially originating from micrometeors. Their presence provides scientists with insights into atmospheric conditions and even climate change, as their increasing frequency and appearance at lower latitudes may indicate changes in the upper atmosphere.
Studying the mesosphere poses difficulties because it is too high for weather balloons and most aircraft, yet too low for satellites to orbit within its bounds due to atmospheric drag. Scientists primarily rely on sounding rockets for brief measurements or advanced radar systems that track meteor trails to gather data. Understanding this layer is important for modeling atmospheric dynamics, chemistry, and energy balance, as processes here can influence global circulation and long-term weather patterns. Research indicates that the mesosphere has been gradually cooling and contracting over decades due to increased greenhouse gas concentrations, demonstrating a complex interaction with climate change.