No, the mesosphere and the mantle are not the same thing. They are completely different structures in different parts of the Earth:

* Mesosphere: A layer of Earth's atmosphere located between the stratosphere and the thermosphere. It is characterized by decreasing temperature with altitude.

* Mantle: A layer of Earth's interior located between the crust and the outer core. It is primarily made of solid rock, but it can behave like a viscous fluid over very long timescales.

Here's a table to clarify:

| Feature | Mesosphere | Mantle |

|---|---|---|

| Location | Atmosphere | Interior |

| Composition | Gases (nitrogen, oxygen, etc.) | Solid rock (silicates, iron, etc.) |

| Temperature | Decreases with altitude | Increases with depth |

| Role | Protection from meteoroids | Drives plate tectonics, volcanism |

Essentially, the mesosphere is a layer of air, while the mantle is a layer of rock.