There are 288 discovered natural satellites – or moons, as they are colloquially known – in the Solar system. Most of these are found in the outer gas giants. However, many of these have not received proper names as they were discovered recently and have yet to be confirmed. Only 164 moons have proper names.
Out of those, there are 5 moons whose names start with the letter I. These are all listed in the following table. Below you will also find some additional details about each, including physical characteristics, the original meaning of their names, etc.
| Moon Name | Planet | Name Meaning |
|---|---|---|
| Iapetus | Saturn | One of the Titans. Father of Atlas and Prometheus. Also written as Japetus |
| Ijiraq | Saturn | Shapeshifting creature in Inuit mythology |
| Io | Jupiter | Ancestor to Perseus, Cadmus, Heracles, and Minos |
| Iocaste | Jupiter | Named after Jocasta, daughter of king Menoeceus and wife of Oedipus |
| Isonoe | Jupiter | One of the Danaides. Zeus turned her into a spring after her death |
Iapetus
Discovered by Giovanni Domenico Cassini in 1671, Iapetus is Saturn’s third-largest moon at 1,469 kilometers in diameter. Named after one of the Titans from Greek mythology, it’s famous for its dramatic two-toned appearance – one hemisphere is bright as snow, while the other is dark as coal. This unique coloration led to it being called the “yin-yang moon.” Iapetus orbits Saturn at a distance of 3.56 million kilometers and has a prominent equatorial ridge that makes it look like a walnut. The ridge, which stands up to 13 kilometers high, runs almost exactly along the equator for 1,300 kilometers.
Ijiraq
Discovered in 2000 by J.J. Kavelaars and his team, Ijiraq is one of Saturn’s irregular satellites. Named after a creature from Inuit mythology capable of shapeshifting and kidnapping children, this small moon is approximately 12 kilometers in diameter. It follows a prograde orbit at an average distance of 11.1 million kilometers from Saturn. Uniquely among Saturn’s moons, it was named from Inuit mythology rather than Greco-Roman or Norse mythology, as suggested by the Canadian astronomers who discovered it.
Io
Discovered by Galileo Galilei in 1610, Io is Jupiter’s innermost Galilean moon and the most volcanically active body in the solar system. Named after a priestess of Hera who was one of Zeus’s lovers in Greek mythology, Io measures 3,642 kilometers in diameter. Its surface is dotted with hundreds of volcanoes, some shooting plumes of sulfur as high as 500 kilometers into space. The intense volcanic activity is caused by tidal heating from friction generated within Io’s interior by its orbital resonance with Europa and Ganymede. Io completes an orbit around Jupiter every 1.77 Earth days at an average distance of 421,700 kilometers.
Iocaste
Discovered in 2000 by Scott S. Sheppard and his team, Iocaste is one of Jupiter’s irregular satellites. Named after Jocasta from Greek mythology, who was the mother and wife of Oedipus in the tragic myth, this small moon is approximately 5 kilometers in diameter. It orbits Jupiter at an average distance of 21.3 million kilometers in a retrograde direction. Iocaste is a member of the Ananke group, suggesting it originated from a larger body that broke apart through a collision.
Isonoe
Discovered in 2000 by Scott S. Sheppard and his team, Isonoe is one of Jupiter’s irregular satellites. Named after one of the Danaides in Greek mythology who, according to the legend, was transformed into a spring by Zeus after her death. This small moon is approximately 4 kilometers in diameter and orbits Jupiter at an average distance of 23.2 million kilometers. Like many of Jupiter’s irregular satellites, its retrograde orbit suggests it was captured by Jupiter’s gravity rather than forming alongside the planet.
Click on a letter below for a list of moons that begin with it.
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Related:
For more on how moons are named check out this article.