Real photograph: Europa's surface, captured by NASA's Galileo spacecraft. Credit: NASA/JPL-Caltech.
29 kilometres of ice between here and an ocean twice the size of Earth's
Beneath Europa's cracked, radiation-blasted ice sits a salty ocean that may hold twice as much water as every ocean on Earth combined. NASA's Juno spacecraft recently measured that ice shell at roughly 29 kilometres thick — deep enough that no light, and almost nothing else, has reached that water in millions of years. This is an imagined tour of the one thing no real mission has ever done: going down into it.
Real photograph: Europa's surface, captured by NASA's Galileo spacecraft. Credit: NASA/JPL-Caltech.
This isn't guesswork. NASA's Europa Clipper — already on its way, arriving in 2030 — exists specifically to answer the questions this imagined dive skips straight past.
Using data from a 2022 flyby, NASA's Juno mission measured Europa's outer ice shell at roughly 29km (18 miles) thick — thicker than most earlier estimates, published in Nature Astronomy in late 2025.
Estimated at 50-150km deep, Europa's subsurface ocean is salty and in direct contact with a rocky seafloor — the exact conditions that support hydrothermal life on Earth's own ocean floor.
Every real spacecraft to Europa — Clipper included — studies the ice and ocean from orbit or the surface. Actually descending through 29km of ice remains far beyond current engineering.
Below is the imagined tour itself — the part that's fiction. A concept for what descending through Europa's ice into its ocean might actually feel like, moment to moment.
The submersible drops into a fracture in the ice — one of the reddish-brown cracks visible from orbit — and Jupiter's pale light fades within the first hundred metres, replaced by the hum of the hull and a wall of blue-white ice sliding past.
The ice thickens and darkens as you fall, the pressure readout climbing steadily. Occasional pockets of brine, trapped mid-shell for millions of years, drift past the viewport like frozen lightning.
The hull breaches into open water — utterly black, utterly still — and the submersible's lights pick out mineral-streaked rock on a seafloor that has been in the dark since before animal life existed on Earth.
As the submersible rises back through the ice, Jupiter reappears first as a diffuse glow, then a shape — a reminder of just how far beneath a familiar sky this entire dive actually took place.
This is written as a concept, not a promise. No cryobot capable of melting through 29km of ice and returning exists today, even unmanned — real ice-penetrating missions (like a proposed Europa lander) are still years from launch, and a human-carrying version is decades further still. Written here first, in case it's ever worth pitching further.