The names of the planets in our solar system are derived from Roman mythology. Each planet is named after a Roman god or goddess, with the exceptions of Earth and, according to popular belief, Pluto. This leads many to wonder, what is the only planet not named after a Roman god or goddess?
Quick Answers
The planet Earth is the only planet in our solar system not named after a Roman deity. The other seven planets (Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune) all take their names from Roman gods or goddesses. Pluto was also initially believed to be named after the Roman god of the Underworld, but its name actually comes from suggestions by an 11-year-old girl named Venetia Burney.
The Origins of the Planetary Names
The tradition of naming planets after Roman gods and goddesses originated with the Romans themselves. Ancient Roman astronomers named the five planets visible with the naked eye (Mercury, Venus, Mars, Jupiter, and Saturn) after Roman deities because of the importance of mythology in their culture. This tradition was later continued when Uranus and Neptune were discovered in more modern times.
The Romans believed that gods like Jupiter and Mars held power over the heavens and human affairs. It seemed natural to name the planets after these important figures in their mythology. The Romans saw the planets as representations of the gods in the sky.
Mercury
Mercury was named after the Roman mythological god Mercury, the swift messenger of the gods. The planet received this name because it moves quickly across the sky compared to other objects in the night sky.
Venus
Venus was named after the Roman goddess of love and beauty. It received this name because it is the brightest object in the night sky after the Moon. Ancient Romans thought it was the most beautiful planet.
Mars
Mars was named after the Roman god of war because of its red color, which resembles blood. The Romans saw Mars as a symbol of military power and strength.
Jupiter
Jupiter was named after the king of the Roman gods. As the largest planet in the solar system, Jupiter was seen as the most important after the Sun, so it received the name of the supreme Roman deity.
Saturn
Saturn was named after the Roman god of agriculture and time. The planet likely received this name because it is visible for long spans of time compared to other night sky objects.
The Modern Planet Names
The tradition of naming planets after Roman gods was continued even after new planets were discovered using telescopes and other modern astronomical tools.
Uranus
Uranus was the first planet discovered after ancient times, spotted in 1781 by astronomer William Herschel. It was named after Ouranos, the Greek primordial god of the sky.
Neptune
Neptune was discovered in 1846 and named after the Roman god of the sea, an equivalent to the Greek god Poseidon. Its blue color reminded astronomers of the ocean.
The Exceptions: Earth and Pluto
While the other seven planets all take their names from Roman mythology, the planet Earth does not follow this pattern. Earth is the only planet whose English name does not come from Greek or Roman mythology.
The name Earth originated from Old English and Germanic languages. It is derived from words like ‘ertha’ and ‘eor(th)e’, which mean “ground” or “soil.” Earth received its name because it was seen as the planet humans inhabited, unlike the more distant celestial objects orbiting in the heavens.
Pluto was also initially believed not to take its name from mythology like the other planets. When Pluto was discovered in 1930, an 11-year-old British girl named Venetia Burney suggested naming it after the Roman god of the Underworld. However, the name Pluto was favored for other reasons.
Pluto’s name was proposed by astronomer Herbert Hall Turner, who based it on the initials P and L for Percival Lowell, the astronomer who predicted the existence of Pluto. So while Pluto’s name resembles that of the Roman god Pluto, the name’s origins were a coincidence, unlike the intentionally mythological names of the other planets.
| Planet | Name Origin | Named After |
|---|---|---|
| Mercury | Roman God | Messenger God Mercury |
| Venus | Roman Goddess | Goddess of Love Venus |
| Earth | English Origins | The ground/soil |
| Mars | Roman God | God of War Mars |
| Jupiter | Roman God | King of the Gods Jupiter |
| Saturn | Roman God | God of Agriculture Saturn |
| Uranus | Greek Primordial Deity | Personification of the Sky Ouranos |
| Neptune | Roman God | God of the Sea Neptune |
| Pluto | Coincidence | Named for astronomer Percival Lowell |
Why Earth is Different
There are a few reasons why Earth came to receive a name separate from the mythological naming tradition of the other planets:
- Proximity – Earth is the planet that humans inhabit, so it was seen as fundamentally different from the distant celestial objects in the sky.
- Perspective – Ancient cultures saw Earth as the center of the universe, so it occupied a central place in their cosmologies distinct from the heavens.
- Literal meaning – The word “Earth” stems from words meaning ground/soil, reflecting how ancient people saw the planet beneath their feet.
- Multiple creation myths – Many cultures had their own creation stories for how the Earth came to be, so no single mythological source stood out as definitive.
- Lost origin – The word “Earth” predates modern recording of ancient religions and mythologies, so its precise origins are unknown.
Earth has gone by various names in different languages, but its English name derives from literal descriptions of the ground rather than stories about gods. Earth’s special status in the cosmos led people to set it apart from mythologically named celestial objects like Saturn, giving rise to our planet’s unique name.
Pluto’s Reclassification
Pluto was originally classified as the ninth planet from the Sun when it was first discovered in 1930. But beginning in the 1990s, astronomers began to debate whether Pluto truly qualified as a planet.
In 2006, the International Astronomical Union passed a resolution that officially reclassified Pluto as a dwarf planet. The factors that led to this included:
- Small size – Pluto is significantly smaller than the other planets, even smaller than Earth’s Moon.
- Irregular orbit – Pluto has an elongated, eccentric orbit that is tilted compared to the solar system’s planets.
- Composition – Pluto is composed mostly of ice and rock, unlike the gas giants Jupiter and Saturn.
- Shared features – Pluto shares many attributes with objects like Eris in the Kuiper Belt region.
Due to not meeting some of the criteria for a full-fledged planet like having cleared its neighborhood of debris, Pluto lost its planet status after only 76 years. However, Pluto remains culturally important as one of the solar system’s most famous dwarfs planets.
Number of Planets Over Time
| Date | Number of Planets |
|---|---|
| Before 1781 | 6 (Mercury, Venus, Earth, Mars, Jupiter, Saturn) |
| 1781 | 7 (Uranus discovery) |
| 1846 | 8 (Neptune discovery) |
| 1930 | 9 (Pluto discovery) |
| 2006 | 8 (Pluto reclassification) |
Conclusion
Earth holds a unique place as the sole planet with a name not derived from Roman mythology. While planets like Mars and Jupiter were named after Roman gods, Earth’s name developed independently to literally mean “ground” in English. Pluto was also initially thought to be an exception, but its name in fact came from suggested initials rather than the Underworld deity.
The tradition of naming the planets after mythological figures originated with the Romans and continues today, underscoring the importance of stories and mythology in understanding humanity’s place in the cosmos. Earth stands alone as the planet named for what lies literally beneath our feet rather than tales of gods in the heavens.
