Earth's Moon: Our own moon is often a favorite because it's the one we can see and study most easily. It has a significant impact on our planet, causing tides and stabilizing Earth's axial tilt.

Titan (Saturn's moon): Titan is the second largest moon in our solar system and it's larger than the planet Mercury. It's the only moon known to have a dense atmosphere, and it has lakes and seas of liquid methane and ethane.

Europa (Jupiter's moon): Europa is slightly smaller than Earth's moon. Scientists are particularly interested in Europa because they believe it has an ocean of liquid water beneath its icy surface, making it a potential habitat for extraterrestrial life.

Enceladus (Saturn's moon): Enceladus is known for its geysers that erupt icy particles, water vapor, and organic molecules into space. Like Europa, it's considered a potential habitat for life.

Io (Jupiter's moon): Io is the most volcanically active object in the solar system, with hundreds of volcanoes, some erupting lava fountains dozens of miles high.

Triton (Neptune's moon): Triton is the only large moon in the solar system that orbits its planet in the opposite direction of the planet's rotation. It's also one of the few moons known to be geologically active.