Callisto, one of Jupiter's moons, does have an extremely thin atmosphere, which is often called an exosphere.

Here's what we know about Callisto's atmosphere:

* Composition: It's primarily made up of carbon dioxide (CO2) with traces of oxygen (O2).

* Density: The atmosphere is incredibly thin, with a density much lower than Earth's. It's about 100 billion times thinner than Earth's atmosphere.

* Origin: The atmosphere is thought to be formed by the sublimation of frozen gases on Callisto's surface, especially carbon dioxide. This process is influenced by solar radiation and micrometeoroid impacts.

While Callisto's atmosphere is extremely tenuous, it is still considered a fascinating feature of the moon. It provides insights into the processes that shape the surface of this icy world.