If you look up at the night sky, you see one moon. It's big, it's bright, and it's basically defined our concept of what a natural satellite is for thousands of years. But honestly, our Moon is a total weirdo. Compared to the rest of the solar system, having just one moon—or no moons at all—is actually the exception, not the rule. When people ask which planets have moons, they usually expect a short list. The reality is a chaotic, crowded orbital dance involving over 200 distinct worlds, ranging from giant spheres of ice to tiny, lumpy space potatoes.
Space is messy. We like to think of the solar system as this clockwork machine where everything is orderly, but the distribution of moons across the eight planets is wildly lopsided. You have the "inner" rocky planets that are basically a ghost town for satellites, and then you have the gas giants, which are essentially mini-solar systems of their own.
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The Inner Circle: Why Mercury and Venus Are Lonely
Let’s start with the losers. Not that they aren't great planets, but if we are talking about which planets have moons, Mercury and Venus are a big zero. They have nothing. No moons, no rings, just vibes.
Why? It basically comes down to location. Mercury is so close to the Sun that any potential moon would be in a constant tug-of-war. The Sun’s massive gravitational pull would either snatch the moon away or pull it into a crash course with Mercury's surface. It’s a "Hill Sphere" problem. A planet’s Hill Sphere is the region where its own gravity dominates over the Sun’s. For Mercury, that region is tiny.
Venus is a bit more of a mystery. It’s bigger, so it has more gravity. Some researchers, like Alex Alemi and David Stevenson from Caltech, have proposed that Venus might have actually had a moon billions of years ago. The theory is that Venus was hit by a massive object, created a moon, and then got hit again by something else that flipped the planet’s rotation. That flip would have caused the moon to spiral inward and get swallowed by the planet. Talk about bad luck.
Earth and Mars: The Rocky Exceptions
Then there's us. Earth has one moon. It’s huge compared to the size of our planet, which is actually quite rare. Most scientists, following the "Giant Impact Hypothesis," believe a Mars-sized object named Theia slammed into Earth about 4.5 billion years ago. The debris eventually clumped together to form the Moon. Without that violent accident, we'd probably be moonless too.
Mars is different. Mars has two moons: Phobos and Deimos. But don't get excited. They aren't majestic like ours. They are tiny. Phobos is only about 13 miles across. They look more like captured asteroids than actual moons, and honestly, that’s exactly what many astronomers think they are. Phobos is actually "doomed." It’s getting closer to Mars by about six feet every hundred years. In about 50 million years, it’ll either crash into the planet or get ripped apart to form a temporary ring.
The Gas Giants: Where the Real Party Is
Once you cross the asteroid belt, the answer to which planets have moons gets insane. Jupiter and Saturn are currently in a cosmic arms race for the most satellites. For a long time, Jupiter was the king. Then Saturn took the lead. As of 2026, Saturn sits at 146 confirmed moons, while Jupiter has 95. These numbers change every few years because our telescopes, like the James Webb Space Telescope and Earth-based observatories using new AI-driven tracking, keep finding tiny new ones.
Jupiter’s Mini-Solar System
Jupiter is basically the boss of the solar system. Its gravity is so intense that it catches everything. The stars of the show are the four "Galilean" moons: Io, Europa, Ganymede, and Callisto.
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- Io is a pizza-colored hellscape of volcanoes. It’s the most volcanically active body in the solar system because Jupiter’s gravity literally squeezes the moon like a stress ball.
- Europa is the one everyone is obsessed with. It’s covered in ice, but underneath that ice is a salty ocean that might have more water than all of Earth’s oceans combined. NASA’s Europa Clipper mission is literally on its way there right now to see if it could host life.
- Ganymede is the biggest moon in the solar system. It’s actually bigger than the planet Mercury. If it orbited the Sun instead of Jupiter, we’d call it a planet.
- Callisto is the old, cratered veteran. It’s one of the most heavily cratered objects we’ve ever seen.
Saturn: The King of Moons
Saturn has the most moons, but most of them are small. However, it does have Titan. Titan is weirdly Earth-like but in a "don't breathe the air" kind of way. It has a thick atmosphere and liquid lakes on the surface. The catch? The lakes are made of liquid methane and ethane, not water. It’s the only other place in the solar system where we’ve seen standing liquid on the surface.
Beyond Titan, Saturn has "shepherd moons" like Pan and Daphnis that live inside the rings and keep the ring particles in line. It’s a delicate, beautiful system that looks like a record player from space.
The Ice Giants: Uranus and Neptune
Uranus has 28 moons (we just found another one recently!). They are mostly named after characters from William Shakespeare and Alexander Pope. Titania and Oberon are the big ones. Uranus is tilted on its side, so its moons orbit at a weird vertical angle compared to the rest of the solar system.
Neptune has 16 moons. The standout is Triton. Triton is special because it orbits Neptune "backward" (retrograde). This is a smoking gun that Neptune didn't "grow" Triton; it kidnapped it. Triton was likely a dwarf planet in the Kuiper Belt that wandered too close and got snagged by Neptune’s gravity.
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| Planet | Number of Moons | Notable Satellites |
|---|---|---|
| Mercury | 0 | None |
| Venus | 0 | None |
| Earth | 1 | The Moon |
| Mars | 2 | Phobos, Deimos |
| Jupiter | 95 | Europa, Ganymede |
| Saturn | 146 | Titan, Enceladus |
| Uranus | 28 | Titania, Miranda |
| Neptune | 16 | Triton |
Common Misconceptions About Planetary Moons
One thing people get wrong is thinking that moons have to be big spheres. Most aren't. Most moons in the outer solar system are just "irregular" moons. They are chunks of rock and ice that look like lumpy potatoes. They don't have enough mass for gravity to pull them into a circle.
Another big one: people think Earth only has one moon. Technically, yes. But we occasionally get "mini-moons"—small asteroids that get caught in Earth's orbit for a few months or years before being flung back out. They are temporary visitors, but for a brief moment, Earth becomes a multi-moon planet.
Then there are "Trojan" asteroids. These are rocks that share an orbit with a planet but don't actually orbit the planet itself. They sit in "Lagrange points" where the gravity of the Sun and the planet cancel out. Jupiter has thousands of them. They aren't moons, but they are part of the planet's gravitational family.
Why Should We Care?
Knowing which planets have moons isn't just for trivia night. Moons are our best chance of finding alien life. While Mars is a dry desert, moons like Enceladus (Saturn) and Europa (Jupiter) have active geysers shooting water into space. We’ve literally flown spacecraft through the plumes of Enceladus and tasted organic molecules.
If we ever become a multi-planetary species, these moons will be our "gas stations." We can mine ice from them for water and fuel. They are the stepping stones to the rest of the galaxy.
Actionable Insights for Amateur Astronomers
If you want to see these moons yourself, you don't need a multi-billion dollar telescope.
- Binoculars are enough: If you have a decent pair of 10x50 binoculars, you can actually see the four Galilean moons of Jupiter. They look like tiny white dots lined up next to the planet.
- Track the positions: Use an app like Stellarium or SkySafari. Since the moons move fast, their positions change every single night. It’s fun to watch Ganymede "hide" behind Jupiter and pop out the other side.
- Look for Titan: With a basic backyard telescope (4-inch aperture or larger), you can easily spot Saturn’s largest moon, Titan. It looks like a faint star very close to the rings.
- Follow the Missions: Keep an eye on the JUICE (JUpiter ICy moons Explorer) mission and Europa Clipper. They are currently in transit or beginning operations and will be sending back high-resolution images of these water worlds over the next decade.
The solar system is a lot more crowded than your elementary school textbook led you to believe. Whether it's the volcanic chaos of Io or the silent, frozen oceans of Enceladus, these moons are where the real action is happening. We’re just starting to scratch the surface of what these 200+ worlds have to hide.
Next Steps for Exploration:
Check the current moon phase and planetary alignment for your location using the NASA Night Sky Network. Focus on Jupiter during its "opposition" (when it's closest to Earth) to get the clearest view of its moon system through even a cheap pair of binoculars. If you're interested in the chemistry of these worlds, look up the recent findings from the Cassini mission regarding the "Tiger Stripes" on Enceladus—it’s the most likely place in our solar system to find active biological markers today.