How Many Moons Does Jupiter Have – 101 Known and Still Counting

For centuries, stargazers have wondered how many moons orbit the solar system’s largest planet. The answer has changed dramatically in recent years. As of March 2026, Jupiter has 101 officially recognized moons, according to NASA. That number is already higher in some catalogs that include newly confirmed moonlets, and the total continues to climb as telescopes improve.

Jupiter’s moon system is a study in extremes. Four giant worlds—Io, Europa, Ganymede, and Callisto—dominate the system, while hundreds of tiny, irregular objects swarm in distant orbits. The latest count also places Jupiter behind Saturn in the moon race: Saturn now leads with 285 known moons after a series of large discovery batches announced in 2023, 2025, and 2026.

Understanding the number of moons around Jupiter requires looking at different sources, confirmation processes, and the difference between “officially recognized” satellites and provisional detections. Here is what the data shows and why the tally keeps evolving.

How Many Moons Does Jupiter Have?

Key insights about Jupiter’s moons

• Jupiter’s moon count is fluid – new moonlets are discovered frequently as telescope technology improves.
• The four Galilean moons (Io, Europa, Ganymede, Callisto) account for more than 99.9% of the mass orbiting Jupiter.
• Most of Jupiter’s smaller moons are likely captured asteroids or comets, not original solar system material.
• Europa is a top candidate for extraterrestrial life due to its subsurface ocean.
• Saturn now holds the record for the most moons in the solar system, overtaking Jupiter again after several back-and-forth changes.
• Official counts from NASA and the IAU Minor Planet Center may differ because of different confirmation thresholds and update timing.

Moon counts are from NASA and the IAU as of early 2026. Jupiter’s number reflects the officially recognized total; provisional discoveries push it to 115 in some catalogs.

How Does Jupiter’s Moon Count Compare to Other Planets?

Jupiter vs Saturn: which has more moons?

Saturn currently leads with 285 confirmed moons after the latest announcements in 2026. Jupiter has 101 in the NASA public count, though other catalogs that include recently confirmed moonlets list 115 as of April 2026. The back-and-forth between the two giants reflects the speed of discovery: Saturn gained 128 new moons in March 2025 alone, while Jupiter added 4 in March 2026 and 14 more in April 2026. Both planets have hundreds of tiny, irregular satellites that are still being found.

Why Jupiter has so many moons compared to inner planets

Jupiter’s immense gravity and location near the asteroid belt allow it to capture many small bodies. Most of its new moons are irregular – small, faint, and likely captured objects or fragments from collisions. The inner planets (Mercury, Venus, Earth, Mars) lack the gravitational reach to hold such swarms. Earth has one large moon, Mars has two tiny ones, and Mercury and Venus have none.

How many moons does Earth have?

Earth has one naturally formed moon, the Moon. It is the fifth largest moon in the solar system, with a diameter of about 3,474 km.

What Are the Four Largest Moons of Jupiter?

Io: the most volcanically active body in the solar system

Io is Jupiter’s third largest moon and the most volcanically active world known. Its surface is covered with sulfur and lava flows from hundreds of volcanoes, driven by tidal heating from Jupiter’s gravity.

Europa: a moon with a subsurface ocean

Europa is about 90% the size of Earth’s Moon. Beneath its icy crust lies a global saltwater ocean that makes it a primary target in the search for life beyond Earth. NASA’s Europa Clipper mission, launched in 2024, is scheduled to arrive in 2030 to study this ocean world.

Ganymede: the largest moon in the solar system

With a diameter of 5,268 km, Ganymede is larger than the planet Mercury. It is the only moon known to have its own magnetic field and a subsurface ocean.

Callisto: a heavily cratered ancient world

Callisto is Jupiter’s second largest moon and the third largest in the solar system. Its surface is the most heavily cratered of any body in the solar system, indicating it has been geologically inactive for billions of years.

How Were Jupiter’s Newest Moons Discovered?

Galileo’s 1610 discovery of the Galilean moons

Using a simple telescope, Galileo Galilei observed four points of light moving around Jupiter in 1610. Those moons—Io, Europa, Ganymede, and Callisto—revolutionized astronomy by proving that not everything orbits Earth.

Major discoveries in the 20th and 21st centuries

The next moon, Amalthea, was discovered in 1892, nearly 300 years after Galileo. The Voyager missions in 1979 imaged Jupiter and found additional moons. But the real explosion came in the 2000s when ground-based telescopes began detecting dozens of tiny irregular moons, each a few kilometers across.

2023–2026: a wave of new announcements

In May 2023, the IAU Minor Planet Center announced 12 new moons of Jupiter, briefly giving the planet the solar system’s highest moon count. Then in March 2025, Saturn gained 128 new moons in a single batch, reclaiming the lead. Jupiter added 4 new moons in March 2026 and another 14 in April 2026 (in some catalogs), while Saturn added 11 more in March 2026. The newly found objects are very small—around 3 km on average—with wide orbits and low brightness, making them challenging to detect.

A Timeline of Jupiter Moon Discoveries

1. 1610 – Galileo Galilei discovers Io, Europa, Ganymede, and Callisto.
2. 1892 – Amalthea discovered, the first non-Galilean moon.
3. 1979 – Voyager missions image Jupiter and find additional moons.
4. 2000–2010 – Ground-based telescopes uncover dozens of tiny irregular moons.
5. 2023 – 12 new moons announced, pushing total to 92 (record at that time).
6. 2025 – Additional confirmations bring Jupiter to 95 in NASA’s count.
7. March 2026 – 4 new moons announced by the Minor Planet Center.
8. April 2026 – 14 more moons confirmed in some catalogs, raising total to 115.

What Is the Certainty of Jupiter’s Moon Count?

Why Does Jupiter Have So Many Moons?

Jupiter’s immense gravity and its position at the edge of the asteroid belt make it a natural trap for passing bodies. The planet’s massive magnetosphere also helps retain captured objects. The four Galilean moons formed from a circumplanetary disk early in Jupiter’s history, while the hundreds of tiny irregular moons are likely captured asteroids, comets, or fragments from collisions. This dual origin explains why the moon system contains both giant worlds and a cloud of small debris.

The count of 101 (or 115) is almost certain to increase. The Vera C. Rubin Observatory, expected to begin full operations in 2025, will scan the sky for faint objects and could discover many more small moons around both Jupiter and Saturn.

Where Can I Find the Official Jupiter Moon Count?

The most authoritative source is NASA’s Jupiter Moons page, which is maintained by the agency’s planetary science division. The International Astronomical Union’s Minor Planet Center also publishes official confirmations. Below are key references:

“Jupiter has 101 known moons. The largest four are called Io, Europa, Ganymede, and Callisto.”

— NASA – Jupiter Moons page, science.nasa.gov

“As of March 2025, Jupiter has 95 known moons.” (Since updated to 101 as of March 2026)

— Cool Cosmos (Caltech/IPAC), coolcosmos.ipac.caltech.edu

“Jupiter, for instance, has 101 known moons!”

— NASA Space Place, spaceplace.nasa.gov

Other useful sources include the IAU announcement on new moons, Space.com’s coverage, and Wikipedia’s list of Jupiter’s moons, though the latter may track provisional objects.

How Many Moons Does Jupiter Have? The Bottom Line

Jupiter has 101 officially recognized moons as of March 2026, according to NASA. Some catalogs that include recently confirmed but not yet fully curated objects list as many as 115. The number will continue to rise as telescopes improve. For the most up-to-date figure, check NASA’s Jupiter moons page. Meanwhile, Saturn remains the current moon champion of the solar system with 285 known satellites.

Frequently Asked Questions