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Moons of the Solar System

Our Moon has a lot of company

Hundreds of moons circle the planets of our solar system: volcanic Io, ocean worlds like Europa and Enceladus, hazy Titan, backwards Triton and tiny Phobos. Here is how they compare with our Moon, and which ones might even host life.

Jupiter's four largest moons side by side: yellow Io, white Europa, grey-brown Ganymede and dark Callisto

NASA/JPL/DLR, Galileo (PIA01299). Public domain.

Size lineup

Big moons drawn to scale, with our Moon outlined in gold. Mercury and the dwarf planet Pluto are dashed for comparison.

Our Moon is the fifth-largest moon in the solar system. Ganymede and Titan are bigger than the planet Mercury, though less massive. Diameters: NASA/JPL.

How many moons does each planet have?

Mercury0
Venus0
Earth1
Mars2
Jupiter115
Saturn293
Uranus29
Neptune16
Pluto5

Confirmed moons recognised by the International Astronomical Union and NASA, late 2026. The numbers keep growing as telescopes find more small, distant moons, mostly a few kilometres across. Pluto is a dwarf planet.

Pick a planet

Tap a planet to see its biggest moons drawn to scale next to ours. The pick is saved in the link, so you can share it.

Jupiter's four largest moons side by side: yellow Io, white Europa, grey-brown Ganymede and dark Callisto

Jupiter: 115 known moons

A mini solar system. The four big Galilean moons include Io, the most volcanic world known, and Europa and Ganymede with hidden oceans.

  • Ganymede5,268 kmLargest moon, own magnetic field
  • Callisto4,821 kmMost cratered surface known
  • Io3,643 kmHundreds of active volcanoes
  • Europa3,122 kmSalty ocean under the ice
  • Our Moon3,475 kmFor scale
  • Ganymede is bigger than the planet Mercury
  • Europa Clipper arrives in 2030

Explore the moons of Jupiter →

What counts as a moon?

A moon (or natural satellite) is any natural body that orbits a planet, dwarf planet or even an asteroid. There is no minimum size, so some "moons" are only a kilometre or two wide. Many small moons are probably captured asteroids or fragments from collisions, and many orbit backwards or on steep, tilted paths.

Our Moon is unusual. It is very large compared with its planet (more than a quarter of Earth's width), and it probably formed from a giant impact. Of the rocky planets, only Earth and Mars have moons, and Mars's two are tiny.

Ocean worlds: where life might hide

One of the biggest discoveries of the space age is that some icy moons hide oceans of liquid water under their frozen crusts, kept warm by the squeezing and stretching of tides from their giant planets.

Life as we know it needs three things: liquid water, the right chemical ingredients (like carbon, nitrogen and phosphorus), and a source of energy. Europa, Enceladus and maybe Ganymede, Titan and Triton may have all three. Each system page has a "Could life be here?" card for every major moon.

Our own Moon is not on that list: it has ice in dark craters but no liquid water. See Water & Ice.

Illustration of Europa cut open to show an ice shell over a deep ocean and hydrothermal vents on a rocky seafloor
AI-generated illustrationEuropa cut open: an ice shell over a deep salty ocean, with possible hydrothermal vents on the seafloor.AI-generated illustration for BotBuhdy.

Explore each system

Phobos, Mars's larger moon: a lumpy, potato-shaped body with the big Stickney crater

Mars: Phobos & Deimos

Two tiny, lumpy moons, Phobos and Deimos, probably captured asteroids or debris from a giant impact. Phobos is slowly spiralling in and will one day break apart.

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Jupiter's four largest moons side by side: yellow Io, white Europa, grey-brown Ganymede and dark Callisto

Jupiter's Moons

A mini solar system. The four big Galilean moons include Io, the most volcanic world known, and Europa and Ganymede with hidden oceans.

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Orange Titan passing in front of pale Saturn and its thin rings

Saturn's Moons

The record holder for moons. Titan has thick air, rain and seas of liquid methane; little Enceladus sprays its ocean into space.

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Uranus's moon Miranda, a patchwork of grooved and cratered terrain with giant cliffs

Uranus's Moons

Icy moons named after characters from Shakespeare and Alexander Pope. Miranda looks as if it was smashed and glued back together.

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Triton's pinkish and grey icy south polar cap with dark streaks from nitrogen geysers

Neptune: Triton

Triton orbits backwards, so it was probably captured from the Kuiper Belt. Voyager 2 saw nitrogen geysers on its frozen surface.

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Pluto's moon Charon in enhanced colour, with a dark red north polar region and a band of canyons

Pluto: Charon

Pluto and its giant moon Charon face each other forever, a double world. Charon has a rusty red cap made from gas that escaped Pluto.

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Quick answers

Which planet has the most moons?

Saturn, with 293 confirmed moons as of 2026, far ahead of Jupiter with 115. Most are small irregular moons a few kilometres across.

What is the biggest moon in the solar system?

Jupiter's Ganymede, 5,268 km across. It is larger than the planet Mercury. Saturn's Titan is second.

Where is our Moon in the size ranking?

Fifth largest, after Ganymede, Titan, Callisto and Io.

Which moons might have life?

The best candidates are ocean worlds: Saturn's Enceladus and Jupiter's Europa, followed by Titan and Ganymede. No life has been found anywhere beyond Earth so far.

Do Mercury and Venus have moons?

No. They are the only planets without any moons.

Sources and credits

  1. NASA Science, Moons of the solar system and planet moon pages (2026 counts).
  2. NASA JPL Solar System Dynamics, Planetary satellite data.
  3. NASA, Europa Clipper and Dragonfly.
  4. Images: NASA/JPL Galileo, Cassini, Voyager 2, New Horizons and Mars Reconnaissance Orbiter (public domain).

Photos credited to NASA, NOAA and other public-domain sources are used with thanks; BotBuhdy adds a small botbuhdy.com mark. Pictures labelled AI-generated illustration are artist-style illustrations made for this page, not photographs.