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From Atmospheres to Oceans: Assessing Water on Habitable Zone Exoplanets

Discover how researchers are pioneering new methods to estimate the water content of exoplanets in habitable zones, moving beyond traditional atmospheric detection techniques. This insightful article delves into the innovative modeling approach led by Adam Boldog, which assesses the potential for surface and subsurface oceans on planets orbiting red dwarf stars and beyond. Understand the significance of radiogenic and tidal heating in supporting life, and explore the intriguing findings related to ocean worlds and the TRAPPIST-1 planets. Join us in rethinking the possibilities for life in the cosmos.

The Quest for Habitable Exoplanets

Astronomers have identified around 60 rocky exoplanets in the habitable zones of their stars, sparking curiosity about their potential for life. The presence of water is a key factor in considering a planet’s habitability. Traditionally, scientists have focused on detecting water in exoplanet atmospheres, but new research is broadening our understanding.

A New Approach to Finding Water

A team of scientists, led by Adam Boldog, is pioneering a method to estimate the water content of these distant worlds without solely relying on atmospheric data. Their innovative modeling technique examines the internal structure of exoplanets to predict the presence of surface or subsurface oceans.

An artist’s conception of a violent flare erupting from a red dwarf star. Such flares can obliterate the atmospheres of nearby planets. Credit: NRAO/S. Dagnello.

The Challenge of Red Dwarf Systems

Many potentially habitable planets orbit red dwarf stars, which are known for intense flaring that could strip planets of their atmospheres, and with it, any surface water. However, these planets might still host vast amounts of liquid water beneath their surfaces, akin to the ocean moons in our Solar System.

How the Study Works

The researchers modeled 28 rocky exoplanets, taking into account factors like radiogenic and tidal heating, to assess the likelihood of thick ocean layers. This method provides insights into the potential for habitability beyond the traditional markers of surface water and atmospheric composition.

Findings That Expand Our Horizons

  • Ocean Worlds: Several planets studied may have enough water to be considered ocean worlds, potentially with surface or subsurface oceans.
  • TRAPPIST-1 Planets: These well-studied worlds are likely to have extended water layers, enhancing their prospects for supporting life.
  • The Role of Heat: Both radiogenic and tidal heating are crucial in maintaining liquid water, either on the surface or underground.
This is a Hubble image of our closest stellar neighbour, Proxima Centauri. Proxima Centauri b is a rocky exoplanet in the star’s habitable zone. Credit: ESA/Hubble & NASA

The Bigger Picture

This research underscores the diversity of habitable environments and the need for innovative approaches to studying exoplanets. While direct observation remains challenging, these models help scientists make informed guesses about where life might thrive beyond Earth.

Embracing the Unknown

The study acknowledges uncertainties, such as the exact amount of radiogenic elements in exoplanet mantles or the impact of tidal heating over time. Yet, it opens up exciting possibilities for the existence of water-rich worlds, potentially teeming with life.

A Universe of Potential

The idea that Earth-like conditions for life might be rare or unique is challenged by the possibility of subsurface oceans as cradles for life. This research invites us to reconsider our place in the cosmos and the myriad ways life might find a foothold on distant worlds.


While we can’t yet directly observe these potential ocean worlds, studies like this one play a crucial role in guiding future exploration and expanding our understanding of habitability in the universe. It’s a reminder of the vast unknowns waiting to be discovered and the innovative approaches we’ll need to uncover them.