Earth’s atmosphere is a complex system of distinct layers, each with unique characteristics. These layers collectively protect our planet and enable life. Among them is the mesosphere, a region that plays a subtle yet important role in atmospheric processes and planetary defense.
Defining the Mesosphere
The mesosphere is located directly above the stratosphere and below the thermosphere. It extends from about 50 kilometers (31 miles) to 90 kilometers (56 miles) above Earth’s surface. A defining characteristic of this layer is its temperature profile, where temperatures steadily decrease with increasing altitude.
This temperature drop is significant, with the upper boundary of the mesosphere, known as the mesopause, being the coldest region in Earth’s atmosphere. Temperatures at the mesopause can plummet to about -90°C (-130°F). While the air in the mesosphere is considerably thin compared to lower atmospheric layers, it still contains enough gas molecules to create significant effects.
Key Phenomena and Significance
The mesosphere protects Earth. As meteors enter our atmosphere at high speeds, they encounter the relatively thin but sufficient air molecules in the mesosphere. This interaction generates intense friction and heat, causing most incoming meteors to burn up and disintegrate. This process prevents many space rocks from reaching the ground as meteorites.
Another phenomenon observed in this layer is the formation of noctilucent clouds. These rare, shimmering clouds, also known as “night-shining” clouds, are the highest clouds in Earth’s atmosphere, forming at altitudes between 76 and 85 kilometers (47 to 53 miles). Composed of tiny ice crystals, they require the mesosphere’s extremely cold temperatures, typically below -120°C, to form. They are most visible during twilight hours at high latitudes in the summer.
The extreme cold of the mesopause, reaching temperatures as low as -90°C to -173°C, makes it the coldest naturally occurring place on Earth. This frigid environment is crucial for the formation of noctilucent clouds and provides scientists with valuable insights into atmospheric dynamics and energy transfer. The mesosphere’s position as a transition zone between the lower atmosphere and space also makes it sensitive to external influences from the sun and changes in the lower atmosphere.
Despite its importance, the mesosphere remains one of the least understood atmospheric layers. It is too high for weather balloons and aircraft to reach, and too low for satellites to orbit within for direct, continuous measurements. Scientists primarily rely on sounding rockets, which provide only brief data collection opportunities, to study this elusive region. This limited accessibility challenges for comprehensive research into its processes and interactions.