Enceladus, Saturn’s moon with a hidden ocean


  • Enceladus has an icy surface with massive fissures called “tiger stripes.”

  • NASA’s Cassini spacecraft confirmed Enceladus has the right chemical ingredients for microbial life in its ocean.

  • Enceladus’ hydrothermal vents may be similar to the ones that helped life flourish on early Earth.

While it’s not Saturn’s biggest moon (that distinction belongs to Titan) or even its closest satellite, Enceladus makes a strong case for being one of its host planet’s most captivating worlds. Not every moon can boast that it creates its own planetary ring, if a moon could boast at all.

Even more surprisingly, somewhere beneath the so-called “tiger stripes” of Enceladus’ icy crust is an ocean that harbors the ingredients necessary for life. Though a few spacecraft have studied Enceladus in the past — most recently, NASA’s Cassini — so much about it remains a mystery. By peeling back the layers of this tiny, fissured world, we can learn about the building blocks of life and how it may exist outside Earth.

Why do we study Enceladus?

In 2015, Cassini made a groundbreaking discovery after plunging through one of Enceladus’ plumes, a massive spray of water vapor gushing from the moon into space. Within the plume, Cassini detected molecular hydrogen, a gas that has been described as “candy for microbes.” Cassini scientists concluded that Enceladus’ plumes contain material from the moon’s underground ocean, which is pushed up by hydrothermal vents on the seafloor. Material then ejects out through the tiger stripes.

Cassini didn’t detect life on Enceladus. But it did confirm the moon has the right components for life: water, energy sources from hydrothermal vents, and certain chemicals (e.g. carbon, hydrogen, nitrogen, oxygen). At this point there are many more questions than answers about Enceladus’ ocean and what it might hold — it’s a good reason to someday go back.

Enceladus in view
Enceladus in view This false-color image was assembled using infrared, green, and ultraviolet filtered images (IR3/GRN/UV3).Image: NASA / JPL-Caltech / SSI / Kevin M. Gill

Enceladus Facts

Surface temperature: -201 degrees Celsius (-330 degrees Fahrenheit)

Average distance from Sun: 9.5 AU

Diameter: 504 kilometers (313 miles)

Volume: 67.1 million cubic kilometers (roughly 16 million cubic miles)

Gravity: 0.113 m/s²

Solar day: 32.9 hours

Solar year: N/A

Atmosphere: Mostly water vapor; small amounts of nitrogen, carbon dioxide and methane

Enceladus and early Earth

There’s a popular idea that life on Earth began about 4 billion years ago on stretches of ocean floor where sunlight couldn’t reach. Here, warm water came into contact with Earth’s rocky crust, causing hydrothermal vents on the bottom of the ocean to release chemical food for life, including molecular hydrogen.

Life was able to flourish around these hydrothermal vents, feeding off the nutrients released through these underwater chimneys. Cassini’s findings would suggest that these conditions on early Earth might be similar to the ones on present-day Enceladus — therefore, microbial life could be hiding somewhere in the moon’s salty depths.

Even with our best guesses, we can’t say for certain how life came to be on our planet. We certainly can’t confirm that there is — or ever was — something life-like on Enceladus. What we do have are clues that deserve further inspection; leads that illuminate what kind of life may bloom in darkness.