Alex McColgan

Cassini's initial photos and infrared images from 2006 showed significant heat at the South Pole.

This incredible photo shows the famous tiger stripes, long fissures in the icy crust, hinting at the activity below.

and clearly some form of a liquid ocean exists here, potentially with hydrothermal activity that powers the huge ice plumes.

For years, scientists believed this ocean was small and lens-shaped.

However, by meticulously tracking surface features over seven years, they noticed the moon librates, or wobbles, a lot more than would be possible with just a small polar ocean.

This finding led to an astonishing realization.

The core isn't rigidly connected to the surface,

We are now confident that the ocean covers the rocky core across its entire surface.

In 2025, there was another breakthrough.

Scientists from the University of Oxford, Southwest Research Institute and the Planetary Science Institute looked back through the Cassini observations of the North Pole from its winter in 2005 and summer in 2015.

They found that not only was heat escaping at the South Pole, but also at the North Pole.

It was 7 degrees warmer than they expected.

This result tells us that Enceladus is generating a lot more internal heat than we thought, and suggests the ocean may have been there for a while.

But, this far from the sun, it is bitterly cold.

As I mentioned, the surface temperature of Enceladus is minus 201 degrees Celsius.

There is no way water should be liquid.

So, next on the list for scientists to check out was energy.

Where was the heat coming from?

If Encella does generated heat by radioactive decay in its core, like Earth does, the energy produced would only be 1% of what Cassini was witnessing.

So in 2017, a team led by Gail Schoble proposed a solution.