A natural satellite, commonly called a moon, is a celestial body that orbits a planet in the Solar System. The official counts of these satellites are constantly changing as advancements in technology allow astronomers to confirm the orbits of smaller, fainter objects. These numbers include only bodies whose paths around the parent planet have been confirmed. This article focuses only on the eight recognized major planets.
The Moons of the Inner Planets
The four planets closest to the Sun—Mercury, Venus, Earth, and Mars—demonstrate a dramatic contrast in their satellite populations. Mercury and Venus possess no natural satellites at all, a condition largely attributed to their close proximity to the Sun. The immense gravitational pull of the Sun makes it nearly impossible for these planets to retain any orbiting material for long periods.
Earth holds a single, large moon, which is unusual because of its size relative to the planet itself. Our Moon’s diameter is about one-quarter that of Earth, making it the largest satellite relative to its host planet among all the major planets. This large ratio suggests a unique formation history, likely involving a massive impact early in the Solar System’s history.
Mars maintains two small, irregularly shaped moons named Phobos and Deimos. These satellites are physically small, with diameters under 15 miles. Their appearance is more akin to lumpy asteroids. Their irregular shapes and close orbits have led scientists to theorize that they are not native to Mars but are instead captured asteroids from the nearby main belt.
Jupiter and Saturn The Satellite Giants
Jupiter and Saturn collectively host the vast majority of the Solar System’s natural satellites. As of late 2025, Jupiter has an impressive count of 97 confirmed moons. This count includes the four large Galilean moons—Io, Europa, Ganymede, and Callisto—which are substantial bodies. Ganymede is the largest moon in the entire Solar System.
Saturn currently holds the record for the most moons, with 274 confirmed satellites. This high number is the result of recent, extensive searches that confirmed the orbits of 128 new, small, irregular moons in early 2025. The majority of these newly confirmed satellites are only a few kilometers across and likely represent fragments from larger objects that were shattered by ancient collisions.
Both gas giants possess a distinct mix of large, geologically complex moons and numerous small, outer satellites. Saturn’s largest moon, Titan, is unique for being the only moon with a dense atmosphere and stable bodies of liquid on its surface.
The Moons of the Ice Giants
Uranus and Neptune, the Solar System’s ice giants, have fewer satellites than their gas giant counterparts, but their systems are complex. Uranus has 29 confirmed moons, all of which orbit a planet that is uniquely tilted on its side relative to the rest of the Solar System. This extreme axial tilt means the entire moon system experiences unusual seasonal cycles.
The naming convention for the Uranian moons is also unique, with its satellites named after characters from the works of William Shakespeare and Alexander Pope. The system is dominated by five large, icy moons, including Miranda, which has a surface showing evidence of intense geological activity.
Neptune has 16 confirmed moons, with its largest satellite, Triton, being the most notable. Triton is considered a captured object because it has a retrograde orbit, meaning it circles Neptune in the direction opposite to the planet’s rotation. This unusual orbital direction and its very cold, nitrogen-ice surface make Triton a distinctive satellite.