The Quest for a Liquid State Water Planet: A Speculative Journey

As of August 2023, there is no confirmed exoplanet that is completely covered in liquid water. However, several candidates have been identified that could potentially have large bodies of liquid water. This article explores the possibility of such a planet and the challenges faced by its formation.

The Known Candidates

One notable example is Kepler-22b, which orbits within its star's habitable zone and is often referred to as a "water world". However, its exact composition remains uncertain. Another candidate is TRAPPIST-1e, a part of the TRAPPIST-1 system, which might have conditions suitable for liquid water. These planets continue to fascinate scientists as the search for exoplanets with significant amounts of liquid water progresses.

The Physics and Formation of a Water Planet

It is highly unlikely for a planet to be entirely made of liquid water. Here’s why:

Gravity and Pressure

A planet-sized mass of liquid water would exert immense pressure at its core. This pressure would likely cause the water to compress and change phase, possibly forming high-pressure ice or other exotic forms of water. The extreme conditions at the core could transform the planet's structure in ways that are currently beyond our comprehension.

Formation

Planets form from accretion disks of gas and dust. Imagine a scenario where a planet were to form entirely from water. The gravitational forces required to keep such a planet cohesive and massive would also attract significant amounts of rock and ice, leading to a more complex composition. It is extremely difficult to envision a planet that remains purely water.

Evaporation

Even if a planet were somehow formed entirely of water, it would quickly lose its water to evaporation if it were located in the habitable zone of a star. The intense solar radiation would turn the water into vapor, which could then escape into space. This process would continue until the planet is no longer in a liquid state.

What Would Be Interesting About Such a Planet Hypothetically

While the idea of a water planet is intriguing, its existence would raise several fascinating possibilities:

Unique Atmosphere

A water planet would have a thick, steamy atmosphere, likely with a strong greenhouse effect. This could lead to extreme temperatures, even in regions not directly exposed to the star. The intense heat would create a unique environment that could support life in its deepest, coldest regions where pressure and temperature are more stable.

Potential for Life

While speculative, a water planet could potentially support life in its deepest regions, where conditions are more stable. These environments could harbor microbial life forms adapted to the extreme conditions.

Oceanic Circulation

The planet would experience massive, planet-wide ocean currents driven by heat from its core and the star. These currents could be incredibly powerful, shaping the planet's climate and geology. The dynamics of these currents would be fascinating to study, revealing a planet in constant motion.

Potential for Subsurface Oceans

Even if the top layers of a water planet were vaporized, deep beneath the surface, there might be pressurized oceans. These oceans could potentially host life, demonstrating the resilience and adaptability of life in extreme environments.

The Bottom Line

While the idea of a water planet is intriguing, it remains highly unlikely to exist in reality. However, it is a fascinating thought experiment and a reminder of the diverse possibilities that exist in the universe. The search for exoplanets continues, and with each new discovery, our understanding of the cosmos grows, bringing us closer to the truth about these hypothetical worlds.