Alex McColgan

This acts as a brake, circularising the orbit.

As the orbit becomes more circular, the tidal stretching stops and the heat source turns off.

This is also how we know that the ocean must be new.

If it was ancient, Mimas's orbit would already be circular.

Our best guess is put this cool down happening somewhere on the scale of millions of years.

But who knows, that may or may not be long enough for life to get going.

We are lucky to be living in the brief window where Mimas is an ocean world.

As its orbit settles down, the ocean will eventually begin to refreeze, and this refreezing will be destructive.

As water turns to ice, it expands.

This expansion will push outward on the crust, likely shattering it and creating massive canyons similar to those we see on Charon or Dione.

It turns out that the Mimas we see today is a snapshot of a world in transition, a change that will eventually destroy the moon as we know it.

The story of Mimas is a humbling lesson in planetary science.

For centuries, we saw a cratered grey wasteland and assumed it was devoid of activity.

We saw the Death Star and assumed it was a bringer of destruction, not a cradle of potential habitability.

But nature is far more creative than our assumptions.

The confirmation of an ocean on Mimas suggests that liquid water might be far more common than we ever dared to dream.

If a small, unassuming world like Mimas can hide a global ocean, what about the moons of Uranus?

What about the objects in the Kuiper Belt?

Mimas has taught us that even the dead worlds might have a heartbeat.

We just have to look close enough to find it.