Understanding the Burning of Meteorites in the Mesosphere: A Detailed Explanation
Meteorites, often referred to as meteoroids in space, experience a unique and fascinating process as they enter Earth's atmosphere. They typically encounter intense friction, leading to significant heating and vaporization, mostly within the mesosphere. This phenomenon is not just about disintegration but a complex interplay of aerodynamic forces and atmospheric conditions. Let's delve into the details of this process.
Entry Speed
When meteoroids enter the Earth’s atmosphere, they are moving at incredible speeds, ranging from approximately 11 km/s (25,000 mph) to over 70 km/s (156,000 mph). These high velocities cause a rapid compression of air in front of the meteorite, leading to significant frictional forces.
Friction and Heating
As the meteoroid descends through the atmosphere, it collides with air molecules, creating friction. This friction generates substantial heat, causing the surface of the meteorite to rapidly heat up to thousands of degrees Celsius. This heat can ionize the surrounding air, producing a glowing trail of plasma, commonly observed as a shooting star.
Mesosphere Characteristics
The mesosphere is the atmospheric layer located approximately 50 to 85 kilometers (31 to 53 miles) above the Earth’s surface. It has lower temperatures than the layers above the thermosphere and below the stratosphere. Despite these lower temperatures, the intense heating due to friction still occurs. The pressure and temperature within this layer are just right to cause significant aerodynamic heating, leading to the disintegration of most meteoroids.
Aerodynamics and Atmospheric Pressures
Contrary to popular belief, the burning of meteorites is not simply due to friction against the thin atmosphere. Instead, it's a result of the compression of air and the subsequent rise in temperature due to the high velocity of the falling meteoroid. Think of it as a similar process to compressing air in your bicycle tires.
When compressing air through a valve, such as when you inflate your bicycle tires, you create a significant amount of heat. This is because you are increasing the pressure of the air, and with that, the temperature rises. When you release the air, it cools down.
The same principle applies to meteoroids entering the mesosphere. As they fall at extremely high velocities, they compress the thin air around them, creating a high-pressure area. The temperature rises dramatically, leading to the vaporization and ionization of the meteoroid and its surrounding air.
Complete Burn-up
Most meteoroids are small, and they often disintegrate completely in the mesosphere before reaching the lower atmosphere or the Earth's surface. However, larger meteoroids may survive the journey and eventually land as meteorites. For a meteorite to reach the surface, it must be at least the size of a marble, with a tiny portion finding its way to the ground.
Some meteors falling for a longer period are likely to be larger. Those that burn up within a fraction of a second, such as the luminous "shooting stars" we observe, are typically the size of a grain of sand or even smaller. Some of the fastest meteors can travel at speeds up to 71 km/s (160,000 mph), further intensifying the heating and compression effects.