Final answer:
Saturn's moon Titan has a thick atmosphere composed mostly of nitrogen, along with a significant amount of methane, and is known for its unique surface features and chemistry.
Step-by-step explanation:
The moon that has a thick atmosphere made mostly of nitrogen is Saturn's moon Titan. Titan is unique among moons in the solar system, with a thick atmosphere composed primarily of nitrogen and about 5% methane. It is recognized for its vibrant orange haze resulting from organic compounds known as tholins, imagery of hydrocarbon 'dunes', and evidence of a hydrocarbon cycle similar to the water cycle on Earth. Titan is the only known moon with such a substantial atmosphere, and it has potential for scientific research due to its complex organic chemistry.