The Earth's mesosphere is part of the atmosphere, located above the stratosphere and below the thermosphere, and it primarily consists of gases, mostly nitrogen and oxygen.
However, if you are looking for a layer within the Earth (geological layers), then the lower part of the Earth's mantle, which is also called the mesosphere (or lower mantle), has a different chemical composition compared to the atmospheric mesosphere. The lower mantle is composed mostly of silicate minerals rich in magnesium and iron, such as olivine, pyroxene, and garnet, and has a different physical state and composition compared to the atmospheric layers.
If you need a more specific comparison or context, please clarify!
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