Alex McColgan

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.

Enceladus is tidally locked to Saturn, meaning the Moon only ever shows one face to the planet.

This distorts Enceladus, which creates heat inside the Moon through internal friction, and powers geological activity.

But it's not enough to just generate and radiate the heat, it needs to be physically transported from the core to the ocean above.

How?

Well, incredibly.

It seems that water perfuses the silicate mineral core where it is heated, causing it to rise in focused plumes that pepper the seafloor around the South Pole.

In 2022, a study led by Wan-Ying Han found further proof of these events.

Based on Cassini's data, they created models of Enceladus' icy surface to try and work out the salinity of the ocean.

They found that it's just a little less salty than we find here on Earth, and that means that there must be, or have been, water-rock reactions, or in other words, vents, at some point.

Hydrothermal vents are credited by scientists as powering the origin of life on Earth.

That these vents may also exist on a small moon around a gas giant is an electrifying discovery, because they give us the third requirement for life, chemicals.

Cassini was equipped with a mass spectrometer, an instrument that can identify individual molecules by the mass of their ions.

On its flybys, it detected hydrogen, believed to be a fuel source for early life.

and complicated hydrocarbons containing oxygen, carbon and nitrogen.

But scientists racing to process the huge volume and richness of data couldn't keep up.

Before they could get through it all, the Cassini mission came to an end, and on the 15th of September 2017, it was sent hurtling towards Saturn.