Written by Tadashi

Modified & Updated: 04 Mar 2024

Jessica Corbett

Reviewed by Jessica Corbett

ocean planet facts

Ocean planets are quite common in popular fiction and mythology. However, while rare in reality, ocean planets are scientifically possible. After all, we are living in one: the Earth is the most well-known ocean planet by far. Discover the other potential ocean planets in the universe with these facts.

  1. Water bodies cover 71% of the Earth’s surface.
  2. 96.5% of Earth’s water lies in the oceans.
  3. Scientists suspect that an ocean 10 km deep lies under at least 200 km of ice on Jupiter’s moon of Callisto.
  4. Scientists also suspect an ocean 10 km deep lies under 30 to 40 km of ice on Saturn’s moon of Enceladus.
  5. Saturn’s moon of Titan is also suspected to have an ocean under 50 km of ice.
  1. Theoretical work on the concept of ocean worlds began in the 1970s.
  2. In 1971, Scientists determined that heat from radioactive elements can create underground oceans on large moons.
  3. Scientists determined in 1979 that large moons heat up further from the gravitational effects of their orbits.
  4. From the 1990s up to the present, space telescopes like the Hubble collected evidence of water on the moons of the solar system’s gas giants.
  5. The discovery of the first planets outside of the solar system (exoplanets) took place in 1992.
  6. In 2004, scientists theorized that icy planets forming in outer systems could then migrate into the inner system, where the ice melts and forms oceans.
  7. The Kepler Space Observatory discovered thousands of exoplanets since its launch in 2009, of which at least 50 are like Earth in size.
  8. In 2018, scientists confirmed that worlds with water could also have life of their own.
  9. Also in 2018, the Cassini orbiter confirmed the existence of organic chemicals in the geysers of Saturn’s moon of Enceladus.
  10. As for 2020, scientists have confirmed the discovery of over 4000 exoplanets.
  1. Some volcanoes on gas giants’ moons spew out ice and water vapor, not lava.
  2. Earth’s water came from condensing water vapor from erupting volcanoes, and asteroid impacts.
  3. Evidence suggests Venus was once an ocean world like Earth but became too hot to keep its oceans.
  4. Evidence also suggests Mars was once an ocean world too, but was too small and had too thin an atmosphere to keep its oceans.
  5. Mars still has water in its polar ice caps, and rarely has liquid water in small amounts during the Martian summer.
Table of Contents

Ocean Planet Facts Infographics

Ocean Planet Facts Infographics

Ocean planets are rocky planets with large amounts of liquid on or below its surface.

Gas giants like Jupiter can never be ocean planets. Most of their mass is in the form of gas, with their atmospheres making up 90% of the planet. In the Solar System, only Earth, Mars, Venus, and Mercury are rocky planets. However, Earth is the only ocean planet among them. Despite its name, water isn’t the only liquid that can form an ocean planet. In fact, the lava covering Jupiter’s moon Io, and the methane forming oceans on Saturn’s moon Titan, also count.

mars, ocean planet
Photo by WikiImages from Pixabay

Ocean planets with too much water will have difficulty supporting life.

If water covers the whole planet, the lack of dry land causes the surrounding water to become phosphorus-deficient. On Earth, phosphorus brought to the sea by precipitation fostered the evolution and growth of microorganisms like plankton.

These, in turn, served as the foundation of other organisms. On a more extreme level, if oceans grow too deep, then the water pressure becomes too great that it keeps plate tectonics from working. This inhibits underwater volcanoes, which introduce key elements and chemicals into the water essential for aquatic life.

Ocean planets that get too close to a star lose their water.

The heat of the star turns the water into vapor, which is then broken down by ultraviolet radiation. The hydrogen escapes from the atmosphere, leaving the oxygen behind. This process takes billions of years to finish but ends with an oxygen-rich, hydrogen-poor, and waterless planet behind. This is also why scientists don’t consider the presence of oxygen in exoplanets as a sure sign of life.

Scientists suspect that Jupiter’s moon Europa is made of ice.

Based on images from telescopes and probes, scientists suspect that ice makes up Europa’s crust. Jupiter’s moon Europa has the smoothest surface of any body in the solar system, which backs this theory. Geysers and eruptions of snow and water vapor point to a possible ocean lying 100 km deep beneath the crust.

Scientists theorize that the heat driving water processes behind geysers and eruptions come from various sources. First is heat from the Europa’s core, second is gravitational effects from the moon’s orbit around Jupiter, and finally, Jupiter’s own radiation.

europa, ocean planet
Photo by skeeze from Pixabay

Sandwiches of ice and rock could make up Ganymede.

Ganymede is Jupiter’s largest moon. Studies of images taken of the moon by telescopes and probes suggest that instead of one or two layers, the moon’s body instead has many more. These layers alternate between rock, ice, and liquid water, though scientists also say there’s evidence for a large, underwater ocean on Ganymede. Based on what’s known of its mass though, if Ganymede does have an underwater ocean, it’d have more water than all of Earth’s oceans combined. How’s that for ocean planet facts?

Water makes up the mantle of Neptune’s moon Triton.

Since the volcanoes on Triton erupt ice and water vapor, scientists conclude that its mantle is composed entirely of water. Telescopes also detected unknown solids in the erupted materials. Because of its low mass and temperature, scientists suspect that they’re organic compounds underneath the moon’s surface.

Triton’s distance from the Sun and its large mass is also similar to the Earth. Triton has a hot metallic core which drives reactions in the watery mantle. In turn, this drives the cold volcanoes on the surface.

triton, ocean planet
Photo by NASA from Wikipedia

Water also makes up the Pluto's mantle.

Pluto’s crust undergoes slow geological changes despite no sign of volcanic activity. Much like Triton, scientists theorize that water makes up Pluto’s mantle, heated by radioactive elements in a metallic core. The heat drives water processes, which causes the geological changes on Pluto’s crust.

Scientists think that Kepler-22b could have oceans.

Kepler-22b is an exoplanet 587 light-years away from Earth. It’s more than twice the size of the Earth. Scientists indicate that the planet may have water in large quantities, and thus count as an ocean planet. Scientists estimate that Kepler-22b’s orbit sits between Venus’ and Mars’ orbits around our Sun.

Kepler-452b is another example of an exoplanet that could have oceans.

Kepler-452b is another exoplanet 1,402 light-years away from Earth. It’s also older than our solar system, at over 6 billion years old. Its host star is also 10% brighter and 20% larger than our Sun. Some scientists theorize that with its Earth-like orbit, Kepler-452b lost its oceans millions of years ago, and is now too hot to support life.

Other scientists disagree due to Kepler-452b’s larger size. It’s about 50% bigger than the Earth. This increased mass offsets the star’s greater output, so Kepler-452b could still have oceans, making it an potential ocean planet.

Kepler-62f is so far the exoplanet most like our Earth.

Kepler-62f is an exoplanet 990 light-years away from the Earth. It’s also older than our solar system, at over 7 billion years old. Its host star is dimmer and cooler than the Sun, and Kepler-62f further away from it than Earth is from the Sun. That said, scientists think that Kepler-62f’s greater mass (40% greater than the Earth) lets it keep enough heat to remain an ocean planet.

kepler-62f, ocean planet
Photo by NASA from Wikipedia

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