Alex McColgan

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.

and was vaporised by the planet's atmosphere, in a self-destructive manoeuvre designed to protect potential habitable life on Enceladus and Titan from contamination by Earth-born microbes.

Though Cassini's mission had been completed, ours had not.

An analysis in 2018 had confirmed the existence of ring-shaped organic molecules and simple oxygen-containing molecules, indicating some limited chemistry was occurring.

Another huge boost to the search for life came in 2022, when the last element crucial to life was observed in the data – phosphorus.

With its discovery, we now had all six main elements believed to be necessary for life – carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur, which scientists know by the acronym CHINOPS.

For a while, this felt like the end of the story, but it turns out this particular book had a few more chapters to go.

When scientists first saw the mass spec data from Cassini, they weren't confident in what they were looking at.

It turns out that the spectra of a carefully prepared sample, analysed while stationary in a lab, looks somewhat different to the one obtained by crashing the detector into an ejector at 64,000 km per hour in space.