For decades, the question has haunted astronomers, philosophers, and science fiction enthusiasts alike: If the universe is so vast and the probability of alien civilizations so high, why haven’t we detected any signs of them? This enduring puzzle, known as the Fermi Paradox, continues to challenge our assumptions about life beyond Earth.
Now, a provocative new perspective from a former NASA scientist offers a compelling—and somewhat chilling—explanation. According to Alan Stern, currently with the Southwest Research Institute in Texas, the great majority of extraterrestrial civilizations may be thriving not on dry, Earth-like surfaces, but deep beneath the icy crusts of vast ocean worlds.
Stern presented his hypothesis at the 2017 Division for Planetary Sciences meeting, directly addressing the Fermi Paradox. “Many possible explanations [to this paradox] have been proffered,” he noted. His alternative? “Namely that the great majority of worlds with biology and civilizations are water ocean worlds.”
Life Beneath the Ice
On these water-dominated planets, alien life would enjoy significant natural protection. A thick layer of ice or rock and ice would shield inhabitants from the dangers of space: exploding stars, intense radiation spikes, and other cosmic hazards. The ocean environment itself could provide a stable, buffered setting conducive to the long-term development of complex life.
Yet this same protective barrier creates a profound communication blackout. “Water worlds are naturally cut off from communication by their interior nature below a thick roof of ice or rock and ice, therefore do not easily reveal themselves,” Stern explained. From our vantage point on Earth, scanning the cosmos for radio signals or other technological signatures, these civilizations would remain effectively invisible—hidden beneath frozen shells that prevent any easy outward transmission.
Water Worlds: The Cosmic Norm?
Mounting astronomical evidence suggests that ocean worlds may be far more common in the galaxy than rocky, land-rich planets like our own. Stargazers increasingly believe the majority of habitable worlds are almost entirely covered in water. This raises the intriguing possibility that the dominant forms of intelligent life elsewhere might resemble aquatic creatures more than land-dwelling humanoids—perhaps something akin to the amphibious Mon Calamari species featured in the Star Wars films.
Supporting this view, Dr. Fergus Simpson of the Institute of Cosmos Sciences at the University of Barcelona employed Bayesian probability analysis earlier that year to estimate that the surfaces of most planets are likely more than 90 percent covered in water. His work reinforces the idea that truly Earth-like balances of land and sea could be statistical outliers.
The Challenge of Aquatic Intelligence
However, Simpson remains skeptical about the emergence of highly advanced technological civilizations in such environments. “The main reason I’m skeptical about there being lots of intelligent underwater alien species is that I think it’s harder for aquatic creatures like dolphins to use tools or build a fire,” he observed. The absence of easy access to fire and the physical limitations of manipulating technology underwater could hinder the kind of industrial and scientific progress seen on Earth.
Earth itself offers a telling point of comparison. With only 29 percent of its surface covered by land, our planet is already remarkably watery. The unusual prevalence of exposed continents may have played a crucial role in fostering the environmental conditions necessary for humanity’s technological leap.
Rethinking the Search for ET
Stern’s hypothesis adds a fascinating layer to the ongoing debate surrounding the Fermi Paradox. If most life-bearing worlds are submerged ocean planets, then the silence we observe in the cosmos may not indicate a lack of life—or even intelligent life—but rather the hidden nature of that life beneath impenetrable icy barriers.
As astronomers continue scanning the skies with ever-more-powerful telescopes, this theory serves as a reminder that extraterrestrial intelligence, if it exists, may look and live in ways far different from our expectations. The search for aliens might require us to look not just outward, but to reconsider what “habitable” truly means—and where the bulk of the universe’s civilizations might actually be residing: shivering, perhaps contentedly, at the bottom of chilly, ice-capped oceans far beyond our solar system.