Which Saturnian moon has a nitrogen atmosphere and liquid on its surface?

Which Saturnian moon has a nitrogen atmosphere and liquid on its surface?

• A. Titan
• B. Enceladus
• C. Mimas
• D. Rhea

Answer: (A)

The key idea is recognizing a Saturnian moon that combines a substantial atmosphere with actual liquids on its surface. Titan fits this description: it has a thick atmosphere largely made of nitrogen, with surface pressure about 1.5 times Earth’s, and it also hosts stable liquids on the surface—lakes and seas of liquid methane and ethane. The other moons don’t match both parts. Enceladus has only a very thin atmosphere and an icy surface; it’s famous for geysers of water vapor, not surface liquids. Mimas is essentially airless, a cratered ice world. Rhea has only an extremely tenuous exosphere and no liquid surfaces.

The key idea is recognizing a Saturnian moon that combines a substantial atmosphere with actual liquids on its surface. Titan fits this description: it has a thick atmosphere largely made of nitrogen, with surface pressure about 1.5 times Earth’s, and it also hosts stable liquids on the surface—lakes and seas of liquid methane and ethane.

The other moons don’t match both parts. Enceladus has only a very thin atmosphere and an icy surface; it’s famous for geysers of water vapor, not surface liquids. Mimas is essentially airless, a cratered ice world. Rhea has only an extremely tenuous exosphere and no liquid surfaces.