Our solar system is home to hundreds of moons, but a select few stand out for their sheer size. These largest satellites are not merely rocks in orbit; they are diverse, geologically active worlds that rival the size of some planets.
The Five Largest Moons
The five largest moons in the solar system all orbit Jupiter or Saturn, except for our own moon. Below is a comparison of their size and key characteristics.
|
Moon |
Planet |
Diameter (km) |
Key Feature |
|---|---|---|---|
|
Ganymede |
Jupiter |
5,268 |
Largest moon, larger than the planet Mercury, only moon with its own magnetic field |
|
Titan |
Saturn |
5,149 |
Second largest, has a dense atmosphere and stable bodies of liquid methane/ethane on its surface |
|
Callisto |
Jupiter |
4,821 |
Heavily cratered, geologically "dead" world, potential subsurface ocean |
|
Io |
Jupiter |
3,643 |
Most volcanically active body in the solar system |
|
Earth's Moon |
Earth |
3,474 |
Fifth largest, responsible for ocean tides |
Moons Larger Than Planets
Two of the solar system's moons are actually larger than the planet Mercury.
- Ganymede (Jupiter): At 5,268 km across, Ganymede is the largest moon. It is the only moon known to have its own magnetic field. It is believed to have a massive, deep ocean sandwiched between layers of ice.
- Titan (Saturn): Only slightly smaller than Ganymede, Titan is unique for its dense, orange-hued atmosphere—a feature typically associated with planets. This atmosphere allows for a weather cycle similar to Earth's, but with liquid methane and ethane instead of water.
Other Notable Large Moons
Beyond the top five, other large moons exhibit fascinating characteristics, highlighting the diversity of worlds orbiting the sun.
Europa (Jupiter)
Europa is the sixth-largest moon and is slightly smaller than Earth's Moon. Its smooth, ice-covered surface suggests a vast, global ocean underneath that may harbor conditions for life. Missions, such as the Europa Clipper, are planned to investigate this further.
Triton (Neptune)
The seventh-largest moon, Triton, is unusual because it orbits Neptune in a retrograde (backward) motion, suggesting it was likely captured from the Kuiper Belt. It features plumes of nitrogen ice erupting from its surface.
Titania and Oberon (Uranus)
Uranus's largest moons, Titania and Oberon, rank as the eighth and ninth largest, respectively. They are primarily composed of roughly half water ice and half rock.