How can frozen nitrogen create Triton’s thin atmosphere?

Triton’s thin atmosphere is created through the process of sublimation, where frozen nitrogen on the moon's surface transitions directly from a solid state into a gas.1

Even at the extremely low surface temperatures of approximately 38 K (−390 °F, −235 °C), a sufficient amount of this surface ice sublimes to form a tenuous atmosphere. This resulting atmosphere is very thin, maintaining a near-surface pressure of less than 0.00002 bar. Additionally, active geyserlike plumes have been observed erupting from the surface, where nitrogen gas escapes through vents in the overlying ice, carrying dust particles into the atmosphere.1