The 10 largest moons in the Solar System
Moons, also known as natural satellites, are celestial bodies that orbit planets or dwarf planets in the solar system. They come in various shapes and sizes and are usually solid; only a few have an atmosphere. As of March 2025, more than 891 moons, including orbiting planets, dwarf planets, asteroids, and trans-Neptunian objects, had been discovered in the solar system.
Only celestial bodies with high mass and powerful gravity could afford such luxury. Mercury and Venus have no moons; Mars has only two, but 79 moons revolve around Jupiter at once, and 82 around Saturn. The ten largest moons of the planets of the Solar System are rated “My Planet.”
10 largest moons of the planets of the Solar System
1. Ganymede
Ganymede is Jupiter’s largest Moon and the largest Moon in the Solar system. Its diameter is 5268 km, compared to 3476 km for the Earth. The huge celestial body is covered with a thick layer of water ice, and the temperature on its surface drops to -203 °C. However, scientists suggest that an ocean of liquid water may be hiding in the depths of Ganymede. It is the only solar system satellite with a magnetic field, and the northern lights often blaze over its poles. The scientist Galileo Galilei saw the largest Moon of Jupiter with the first telescope at the beginning of the 17th century.
2. The Titan
Saturn’s giant Moon, Titan, is slightly smaller than Ganymede: its diameter also exceeds 5,000 km, and its weight is 95% of the total mass of Saturn’s 82 moons. Of all the moons in the Solar System, only Titan has a dense atmosphere consisting mainly of nitrogen. On its icy surface are mountains and cryovolcanoes spewing water, ammonia, and methane.
Like on Earth, Titan has seas and lakes that contain methane and ethane instead of water. Astronomers often compare Saturn’s largest Moon with the young Earth and do not exclude the fact that the simplest organisms can live in its underground reservoirs.
3. Callisto
Callisto is Jupiter’s second-largest Moon and third in our ranking. She bears the name of a beautiful nymph from ancient Greek myths, whom Artemis turned into the big dipper and Zeus into the constellation of the same name. But this cold Moon, almost the size of Mercury, does not shine with beauty: its surface is covered with ice and rocks and dotted with craters from falling meteorites.
Multicircular structures resembling amphitheaters have formed around them. The largest is called Valhalla: from the central crater, which has a diameter of 600 km, concentric rings radiate over a distance of about 2000 km.
4. Io
Another large moon of Jupiter is Io. This is one of the most troubled places in the solar system. It has over 400 active volcanoes on its surface, continuously spewing sulfur and sulfur dioxide into the atmosphere. Such violent volcanic activity is explained by its proximity to the largest planet in the Solar system: due to Jupiter’s gravitational influence, Io’s interior is warming up. Lava flows and volcanic ash paint its surface bright colors, and 90% of its thin atmosphere is poisonous sulfur dioxide.
5. Moon
The Moon is the fifth-largest satellite in the Solar System. It is slightly smaller in diameter (3,474 km) than Io and larger in area than Africa but smaller than Asia. Our closest cosmic neighbor is not the most cozy corner of the universe: a thin atmosphere, a black sky, and a temperature difference from -173 °C in the shade to +127 °C in the sun. Several times a year, it is shaken by moonshakes of magnitude up to 5.5. On the surface of the Moon, mountains and lunar seas are adjacent — huge craters filled with frozen basalt lava. Frozen water has been found at the bottom of some craters. What else to see on the Moon? We suggest you take a look at the guide to the main attractions of the Moon.
6. Europa
Europa is a satellite of Jupiter, and its structure resembles terrestrial planets. Visit. A F R I N I K. C O M .For the full article. From above, Europa is covered with a thick layer of smooth ice, under which the ocean is presumably lapping, and below are rocks.
If there is water under the ice, then there is two to three times more of it than on Earth, and living creatures can live there, from extremophile bacteria to fish. According to one version, there is enough oxygen in the ocean of Europa to develop complex life forms, and the tides warm up its waters.
7. Triton
Neptune’s largest Moon is Triton. It is the only large Moon that orbits Neptune in the opposite direction of the planet’s movement. Triton is the coldest Moon in the Solar system: its surface temperature reaches a record-breaking -235 °C, it is covered with water and nitrogen ice, and cryovolcanoes emit liquid nitrogen into the atmosphere.
8. Titania
Titania is a satellite of Uranus. It is a harsh realm of ice and stone: Titania is covered with frozen water and carbon dioxide from above, and there is a stone core inside. The celestial body is covered with huge craters and rugged canyons. It is one of the least studied moons in the Solar System—only Voyager 2 explored Titania from a close distance in 1986.
9. Rhea
Astronomer Giovanni Cassini discovered Rhea and three other large moons of Saturn at the end of the 17th century. He named them Louis Stars in honor of the king of France, and almost 200 years later, he gave her the name of the mother of the Olympian gods. Rhea consists of two-thirds frozen water, and its atmosphere consists of oxygen and carbon dioxide. Scientists suggest that Rhea, like Saturn, has a ring system, but this is only a hypothesis.
10. Oberon
Oberon rounds out the top ten largest natural satellites. This satellite of Uranus consists of ice and rocks, and a large mountain about 6,000 m high stands out on the surface. Due to the peculiarities of Uranus’ rotation (the planet has an ellipsoidal orbit), the seasons on Oberon alternate much less frequently than on Earth: each of its poles is constantly illuminated for 42 years and remains in total darkness for 42 years.
