Enceladus, Saturn’s frozen ocean

If you’ve been following universe news in recent months, you’ll have heard about Enceladus, one of Saturn’s most fascinating moons. It is not the brightest and not the largest, but in 2025, it has once again made headlines with discoveries that raise the hope of finding life outside Earth.

Imagine a world covered in pure ice, with a warm underground ocean rich in organic compounds… Sounds like science fiction, right? Well, it’s real, and today we tell you about this Saturnine gem. Learn more below.

A Little Giant with a Liquid Heart

Enceladus is the sixth largest moon of Saturn and the 18th in the entire solar system. With a diameter of just 504 kilometers, just a little larger than the distance between Madrid and Barcelona, ​​it looks like a cosmic pebble compared to our planet.

Its surface, completely covered in ice, is almost perfectly spherical, making it unique among Saturn’s irregular moons, and is composed primarily of nearly pure water ice, with a high density suggesting a rocky core beneath. But what really makes it special is its underground global ocean, a vast sea of ​​water that extends beneath an ice crust between 16 and 28 kilometers thick.

This moon orbits Saturn every 33 hours about 238,000 kilometers away, which subjects it to intense tidal forces. Saturn “stretches and squeezes” it, generating heat through internal friction, a process called tidal heating. This heat keeps the ocean liquid despite surface temperatures around -200°C.

Mosaic of Saturn’s moon Enceladus, created with images captured by NASA’s Cassini spacecraft on October 9, 2008. Image credit: NASA/JPL/Space Science Institute

Ice Geysers: Windows to the Hidden Ocean

What made Enceladus best known in 2005 was the discovery of its polar geysers. NASA’s Cassini probe detected jets of water vapor and ice particles erupting from “striated tigers,” streak-like fissures at its south pole.

These geysers spew material at speeds of up to 400 meters per second, forming Saturn’s E ring and creating a “tail” of plasma that extends for thousands of kilometers. In fact, the existence of at least 101 erupting geysers has been confirmed.

These jets are not just a visual spectacle; They are direct windows to the ocean. The ejected material contains salts, silica and gases such as hydrogen, methane and carbon dioxide, evidence of hydrothermal activity on the ocean floor, similar to vents on Earth’s seafloor, where early life could have emerged.

In 2017, Cassini “drank” from these geysers and confirmed the presence of phosphates, a key ingredient for DNA and ATP, the “energy currency” of life.

NASA’s Cassini spacecraft captured this image of Enceladus on November 30, 2010. The shadow of Enceladus’s body in the lower parts of the jets is clearly visible. Image credit: NASA/JPL-Caltech/Space Science Institute

Recent Discoveries: Game-Changing Organics and Heat

In 2025, Enceladus continues to surprise us. A study published Oct. 1, based on old Cassini data, revealed a new variety of complex organic compounds in the geysers: esters, alkenes and ethers. These had not been detected before in the Saturn system and come directly from the ocean, analyzing particles captured minutes before their ejection.

This raises Enceladus’ chemistry to a “prebiotic” level, with all the building blocks for life: carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur. But wait, there’s more!

In November, another Cassini analysis showed unexpected heat flow at the north pole, with warmer than expected surface temperatures, in data collected from 2005 to 2015. When the heat from the south pole is added, it releases a total energy of 54 gigawatts, that is two-thirds of the Earth’s geothermal energy. This heat emission is so high that it explains how the moon maintains its liquid ocean.

These new data confirm that the ocean can remain stable for billions of years, ideal for the evolution of microbial life. These findings, from decade-old data, demonstrate how science continues to unravel secrets from the past to illuminate the future and underscore the need for long-term missions to ocean worlds.

14-hour images create this sequence of images from the last dedicated observation of Enceladus’s plume by Cassini. Image credit: NASA/JPL-Caltech/Space Sciences Institute

Life on Enceladus? One Step Closer to the Answer

With a warm ocean, hydrothermal energy, and a rich organic soup, Enceladus meets the three pillars of habitability: liquid water, energy sources, and complex chemistry. Experts like those at the University of Washington call it “the most promising candidate” for extraterrestrial life in the outer solar system.

Microbes on your ocean floor? Or something more exotic? We don’t know yet, but the hydrogen detected suggests microbial metabolism, like in the deep Earth.

NASA plans the Enceladus Life Finder (ELF) mission with a probe that directly surveys geysers for biosignatures. Meanwhile, the James Webb telescope has captured spectra of the jets, and Europa Clipper (launched in 2024) could inspire similar designs. Hopefully we’ll see a “Cassini 2.0” soon!

In conclusion, Enceladus reminds us that life could flourish in the most unexpected places: under ice sheets, on distant moons. In a year like 2025, with these advances, the dream of finding signs of life outside of Earth would be closer.