The vast majority of natural satellites (moons) in the Solar System that orbit planets are tidally locked to their primaries-meaning the same face always points toward the planet they orbit. Here’s a detailed breakdown:
Approximate Statistics:
- There are over 200 known natural satellites of planets in the Solar System.
- More than 99% of the major moons (those large enough to be rounded by their own gravity or well-studied) are tidally locked to their parent planet.
- This includes all the large moons of the gas giants, like:
- Io, Europa, Ganymede, Callisto (Jupiter)
- Titan, Rhea, Iapetus, Dione, Tethys, Enceladus (Saturn)
- Miranda, Ariel, Umbriel, Titania, Oberon (Uranus)
- Triton (Neptune – though retrograde and captured, it is also tidally locked)
The few exceptions are:
- Hyperion (a small, irregularly shaped moon of Saturn) – which tumbles chaotically and is not tidally locked.
- Some very small or recently captured moons (like Neptune’s Nereid) may not yet be locked, or their rotation hasn’t been conclusively measured.
