🧊 Triton — A Deep-Freeze World Triton, Neptune’s largest moon, is the coldest known place in our solar system. Its average surface temperature is about −391°F (−235°C), cold enough that nitrogen gas freezes into solid ice. This frozen nitrogen forms a bright, pale layer across much of the moon’s surface. Yet Triton is far from lifeless or boring. When NASA’s Voyager 2 spacecraft flew past in 1989, it discovered a surprisingly active world. The surface features vast icy plains, long fractures, a