What is the outer layer of the thermosphere that extends outward into space called?

What is the outer layer of the thermosphere that extends outward into space called?

• A. Ionosphere
• B. Exosphere
• C. Thermosphere
• D. Stratosphere

Answer: (B)

The outermost layer extending into space is the exosphere. In this region the atmosphere is incredibly thin, so molecules rarely collide and can travel long distances or even escape Earth's gravity, creating a gradual boundary between air and the vacuum of space. This makes the exosphere the final edge of the atmosphere. The ionosphere is a highly ionized part of the upper atmosphere that affects radio waves, but it lies within the thermosphere rather than forming the outer boundary. The stratosphere sits below the troposphere and is well under the thermosphere, so it isn’t the outermost layer.

The outermost layer extending into space is the exosphere. In this region the atmosphere is incredibly thin, so molecules rarely collide and can travel long distances or even escape Earth's gravity, creating a gradual boundary between air and the vacuum of space. This makes the exosphere the final edge of the atmosphere. The ionosphere is a highly ionized part of the upper atmosphere that affects radio waves, but it lies within the thermosphere rather than forming the outer boundary. The stratosphere sits below the troposphere and is well under the thermosphere, so it isn’t the outermost layer.