Definition of the Mesosphere
The mesosphere is the third layer of Earth's atmosphere, located directly above the stratosphere and extending from about 50 kilometers (31 miles) to 85 kilometers (53 miles) above the Earth's surface. It is characterized by rapidly decreasing temperatures with increasing altitude, making it the coldest region of Earth's atmosphere.
Key Characteristics and Temperature Profile
In the mesosphere, temperatures can plummet to as low as -100 degrees Celsius (-148 degrees Fahrenheit) at its top boundary, known as the mesopause. This severe cooling occurs because there is very little ozone in this layer to absorb solar radiation, and the thin air radiates heat away efficiently. The air density is extremely low, meaning that while it contains gases, they are very sparse.
Role in Meteor Ablation
One of the most significant phenomena occurring in the mesosphere is the burning up of meteors. As meteoroids enter Earth's atmosphere at high speeds, they encounter sufficient atmospheric friction in the mesosphere to heat up intensely and vaporize, creating the luminous streaks we observe as 'shooting stars.' This layer effectively shields Earth's surface from countless incoming space debris.
Research and Observation Challenges
The mesosphere is notoriously difficult to study directly. It is too high for weather balloons and too low for orbiting satellites to maintain a stable trajectory. Scientists primarily use sounding rockets, ground-based radar, and lidar (light detection and ranging) to gather data on its composition, temperatures, and winds, providing insights into its dynamics and its role in the overall atmospheric system.