This page lists 7 moons with names starting with the letter I, ranging from “Io” to “Inarime.” These moons vary widely in size — from massive, volcanically active worlds to tiny rocks in distant orbits. They circle some of the largest planets in our Solar System and have fascinated scientists and space enthusiasts for generations.

Moons are natural satellites that orbit planets, held in place by gravity. They range from planet-sized bodies with rich geology to small captured rocks just a few kilometers wide. Earth’s Moon has inspired mythology and navigation for thousands of years, and the many moons of Jupiter and Saturn continue to reveal new surprises.

Below you’ll find the table with Moon, Parent Planet, Diameter (km), Discovery Year, and Description.

Moon: The name of each moon, which you can use to look it up or compare it with others on this list.

Parent Planet: The planet each moon orbits, helping you understand which part of the Solar System it belongs to.

Diameter (km): The approximate size of the moon in kilometers, giving you a sense of how large or small it is.

Discovery Year: The year astronomers first identified each moon, showing how our knowledge of the Solar System has grown over time.

Description: A brief summary of each moon’s key features, orbit, or history, so you can quickly understand what makes it notable.

Moons

MoonParent PlanetDiameter (km)Discovery Year
IoJupiter3,6431610
IapetusSaturn1,4691671
IjiraqSaturn122000
IocasteJupiter52000
IsonoeJupiter42000
IoneJupiter42000
InarimeJupiter32000

Descriptions

Io
The most volcanically active body in the Solar System, Io is one of Jupiter’s four large Galilean moons. Intense tidal heating from Jupiter’s gravity fuels hundreds of constantly erupting volcanoes across its surface.
Iapetus
One of Saturn’s largest moons, Iapetus is famous for its striking two-toned surface — one hemisphere is as bright as snow while the other is as dark as coal. Giovanni Cassini discovered it in 1671.
Ijiraq
A small irregular moon of Saturn in the Inuit group, named after a shapeshifting creature from Inuit mythology. It follows a highly inclined, eccentric orbit far from Saturn.
Iocaste
A small irregular moon of Jupiter belonging to the Ananke group, orbiting in a retrograde direction. It was discovered along with many other tiny Jovian moons during surveys in 2000.
Isonoe
One of Jupiter’s small irregular moons in the Ananke group, traveling in a retrograde orbit far from the planet. It was found during a survey that uncovered dozens of new Jovian moons.
Ione
A tiny irregular moon of Jupiter in the Ananke group, named after a sea-nymph in Greek mythology. It was among many small moons discovered around Jupiter in 2000 by Scott Sheppard and colleagues.
Inarime
A very small irregular moon of Jupiter in the Ananke group with a retrograde orbit. It is named after an island in ancient Greek mythology, sometimes identified with modern-day Ischia in Italy.
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