Beneath the Ice: Humanity’s First Base on Callisto

Introduction

Callisto, one of Jupiter’s largest moons, has always fascinated me. As a child, I read a comic published in weekly episodes in the Italian magazine Corriere dei Piccoli (translation: “The Children’s Mail”). The story was about Gianni Bibò, a bizarre, overweight, middle-aged, bespectacled astronaut who, together with his rinky-dink android sidekick, Rob-8, was on a mission to explore Callisto, only to discover intelligent alien life dwelling beneath its icy crust. Gianni and Rob-8 left an indelible mark on my imagination, likely contributing to my choice to major in astronomy decades later. It seemed pure science fiction then — a frosty fantasy set in a distant, unreachable corner of the solar system.

But today, that vision feels surprisingly prescient. ¹

Thanks to decades of space exploration and the revelations of robotic missions like Galileo and Juno, we now know that Callisto, along with its sibling moons Europa and Ganymede, likely hides a subsurface ocean beneath its ancient, cratered surface—an environment that could support extraterrestrial life.

Even more intriguing? Callisto may be the most practical location for human habitation in the Jovian system.

Why Callisto?

Callisto is the outermost of the four Galilean moons, orbiting farther from Jupiter than Europa or Ganymede. While this might seem a disadvantage at first glance, it gives Callisto one key feature that makes it ideal for long-term human exploration: it lies mostly outside Jupiter’s deadly radiation belt.

Jupiter’s magnetic field is the strongest of any planet in our solar system. Its inner moons—especially Io and Europa—are bombarded by intense levels of ionizing radiation. Building a base there would require massive shielding, dramatically increasing the cost and complexity of any long-term mission.

On Callisto, those dangers drop dramatically. Astronauts could live and work on the surface with far fewer radiation countermeasures, making it a cost-effective and safer candidate for the Solar System’s first permanent base beyond the asteroid belt.

Life Beneath the Surface?

Callisto’s surface is ancient and heavily cratered, suggesting geological inactivity. But beneath its icy shell, models suggest the presence of a salty liquid ocean, kept warm not by tidal forces (as on Europa or Io), but likely through radioactive decay in its rocky interior.

If that ocean exists—and it almost certainly does—it raises a thrilling question: Could it harbor life?
Simple microbial organisms may thrive in hydrothermal vents as they do on Earth’s ocean floors. Some theorists even speculate about complex ecosystems preserved in isolation for eons.

A future Callisto base could include deep-penetrating probes or cryobot submersibles designed to melt through the ice and explore the dark waters below.

A Blueprint for a Base

Soon — perhaps within the next 50 to 100 years — space agencies or commercial partners might build a modular base on Callisto’s surface, featuring:

• Radiation-hardened habitats, partially buried beneath the ice for added protection.

• Robotic drills and cryobots, slowly boring through the ice to the subsurface ocean.

• Autonomous nuclear or fusion power generators, enabling long-term operations.

• A low-gravity launch system (Callisto’s gravity is just 12.5% of Earth’s) for interplanetary supply chains or orbital research stations.

Callisto could also serve as a stepping stone to exploring Jupiter’s other moons or a remote refuelling station for missions to Saturn or the Kuiper Belt.

From Comics to Cosmos

It’s remarkable how a childhood comic about aliens under Callisto’s ice now echoes real scientific hypotheses. While intelligent civilizations may not greet our astronauts anytime soon, the idea of finding life — even simple microbial life — in a hidden ocean on a Jovian moon would be one of the most significant discoveries in human history.

And if humanity is to become a multi-world species, Callisto may very well be the gateway to a new era of exploration.

---

1. Recently, I tried to retrieve the comic episode in which Gianni and Rob-8 land on Callisto. The illustration that struck me so much at the time showed a Saturn V-like spaceship standing on the moon’s surface while a green alien watched from a nearby icy cave. After a long web search, I found the original April 1969 picture, and I couldn’t believe my eyes: the moon was Titan, Saturn’s largest moon, NOT Callisto! This isn’t possible. Why would I have been so obsessed with Callisto if it wasn’t Callisto? If this isn’t an example of the Mandela Effect, then I don’t know what it is. ↩︎