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Solar System Moons Series

Enceladus

The moon spraying an ocean into space: water geysers feeding Saturn's rings.

Author: Juan Carlos Euyoque Aguilera · October 7, 2026 · CC BY 4.0

Image of Enceladus (NASA/JPL, public domain)
Enceladus and its polar fractures (Cassini spacecraft, NASA/JPL, public domain). Not to scale.
504 km
Diameter
237,948 km
Distance from Saturn
~75 K
Temperature
0.113 m/s²
Gravity

Enceladus, just 504 km across, orbits Saturn at 237,948 km. So small its gravity is 0.113 m/s² — yet it is one of the most active worlds: plumes of water vapor and ice erupt from its south pole, discovered by Cassini in 2005.

Those plumes feed Saturn's E ring and, from Cassini's gravity and libration measurements, come from a global ocean under the ice. Enceladus is now one of the best candidates in the search for life.

Measured data [DATO]

DataValueStatusSource
Diameter504 km[DATO] observadoNASA Planetary Fact Sheets
Mass1.08×10²⁰ kg[DATO] observadoNASA Planetary Fact Sheets
Mean density1,610 kg/m³[DATO] observadoNASA Planetary Fact Sheets
Surface gravity0.113 m/s²[DATO] observadoNASA Planetary Fact Sheets
Orbital period1.370 days[DATO] observadoNASA Planetary Fact Sheets
Rotation periodsynchronous (1.370 days)[DATO] observadoNASA Planetary Fact Sheets
Distance from Saturn237,948 km[DATO] observadoNASA Planetary Fact Sheets
Temperature~75 K (the Tiger Stripes, warmer)[DATO] observadoNASA Science
AtmosphereTenuous: water vapor from the plumes[DATO] observadoNASA Science
Notable featureGlobal ocean under the ice; plumes feed the E ring (Cassini)[DATO] observadoNASA Science

Truths [DATO]

  • [DATO] Cassini flew through Enceladus's plumes and analyzed their composition: water, salts, ammonia and organic molecules — ocean water, not just surface ice.
  • [DATO] The libration (wobble) measured by Cassini only fits if the ice crust floats on a global ocean, not on rock.
  • [DATO] The south pole's 'Tiger Stripes' are ~130 km fractures venting the plumes; tidal heating keeps them active.
  • [DATO] In 2023 the JWST confirmed a huge water-vapor column from Enceladus stretching thousands of kilometers: the E ring, seen live.

Labeled myths [MITO]

[MITO] Enceladus's geysers are boiling water.

False: they are cryovolcanic plumes —vapor and ice crystals erupting into vacuum from fractures, driven by tidal heating; 'boiling' assumes an atmospheric pressure that does not exist there.

Fuente: NASA Science

[MITO] Enceladus is too small to have an ocean.

False: Cassini's libration and gravity measurements confirm a global ocean under the ice; size does not rule — tidal heating does.

Fuente: NASA Science

Open questions [PREGUNTA]

  • [PREGUNTA] Are there active hydrothermal vents on its ocean floor?
  • [PREGUNTA] Is Enceladus's ocean habitable?
  • [PREGUNTA] How long will the plume activity last?

The chain in brief

  1. [DATA] 1. Small, and yet one of the most active: Just 504 km across with a surface gravity of 0.113 m/s², orbiting Saturn at 237,948 km: plumes of water vapor and ice erupt from its south pole, discovered by Cassini in 2005.
  2. [DATA] 2. The tiger stripes that spray an ocean: The south pole's 'Tiger Stripes' are ~130 km fractures venting the plumes, kept active by tidal heating.
  3. [MODEL] 3. A global ocean beneath the ice: The libration measured by Cassini only fits if the ice crust floats on a global ocean, and Cassini flew through the plumes and analyzed their composition: water, salts, ammonia, and organic molecules — ocean water.
  4. [DATA] 4. The E ring is born here: Those plumes feed Saturn's E ring; in 2023 the JWST telescope confirmed a huge water-vapor column from Enceladus stretching thousands of kilometers.
  5. [DISPUTED] 5. A habitable ocean?: Whether there are active hydrothermal vents on its ocean floor, whether that ocean is habitable, and how long the plume activity will last remain open: Enceladus is now one of the best candidates in the search for life.