Which moon of Saturn is known for its thick atmosphere?

Titan is the correct choice because it is the only moon of Saturn that possesses a substantial atmosphere. Its atmosphere is primarily composed of nitrogen, with significant amounts of methane and other organic compounds. This thick atmosphere is unique among the moons of our solar system and plays a crucial role in its surface processes. The presence of this dense atmosphere allows for weather phenomena, including liquid methane lakes, and creates a somewhat Earth-like environment conducive to the potential development of prebiotic chemistry.

In contrast, the other moons listed, such as Tethys, Mimas, and Enceladus, have very thin or negligible atmospheres, primarily composed of trace amounts of gases, making them less capable of supporting any significant atmospheric processes. Thus, Titan stands out distinctly due to its extensive and dense atmosphere, making it a unique body of interest in the study of planetary environments.