Imagine an entire planet where its atmosphere is like that of a sauna. This is what “steam planets” are like. But there’s much more that these exoplanets have to offer than their hot environments. Recent research published in the The Astrophysical Journal ( ) explores how water behaves on exoplanets. These planets are categorized as sub-Neptunes because they have a mass and size between Earth and Neptune.
Even though the absence of liquid water makes it impossible to find life on steam worlds, understanding how they evolved can still help in the hunt for alien life.
Sorting Through Steam Worlds.
In 2024, after decades of predicting the existence of these worlds, James Webb Space Telescope confirmed the sighting. The exoplanet, GJ 9827d, was located nearly 100 light-years away. It had an atmosphere almost exclusively made of hot water vapour. The researchers believe future JWST observations are likely to discover many more exoplanets with a steamy atmosphere like this one.
Steam planets such as GJ 9827d don’t support the type of life found on Earth. They are closer to their star host than Earth is. Liquid water cannot be found at their surface, but there are other forms of water. Under the thick steamy air, there is a layer of “supercritical” water. This strange phase of water has both liquid and gas properties. It is not only found on other planets, but also on Earth. Supercritical water comes from deep ocean hydrothermal vents. The water has been created in labs and is used for waste treatment, nuclear engineering, and bioenergy. The phases of water on steam worlds.
Water in sub-Neptunes can transform from its supercritical and steamy states to “superionic Ice” under extreme temperatures and pressure. This phase occurs when water molecules are reorganized so that hydrogen ions can freely move through the oxygen lattice. Superionic ice has both liquid and solid properties. The researchers were inspired by these unusual water states to develop a better model for steam worlds. These models have been compared with those developed to examine icy moons of our Solar System. The sub-Neptunes are much larger and have no ice crusts. Researchers wanted to know how sub-Neptunes’ water could act as steam, supercritical fluid or in other extreme conditions like superionic liquid. They believe that understanding how exoplanets evolved to have these different forms of water could help them find life on other planets with water. The interiors of the planets provide a natural laboratory for studying conditions which are hard to replicate in an Earth-based university lab. The information we gain could be used in unexpected ways that we hadn’t considered. In this way, water worlds have a unique exotic quality,” Natalie Batalha said in a press release. She is a Professor of Astrophysics and Astronomy at the University of California Santa Cruz.
In the future we might find that some of these water-rich worlds are new niches in which life can exist, Batalha added.
The Search for Alien Life is Full Steam Ahead
By combining information from atmospheric and interior model, researchers developed a new map to show the evolution of an water-rich planet. This model shows that these planets have a smaller radius than previous models predicted, and the deep water in the interior of the planet is cooler than was previously thought. The model also confirms that the water inside a planet’s interior can change from plasma to superionic liquid. The properties of a subNeptune, such as its changing radius and composition over billions years are essential for understanding the evolution. Even though the steam worlds aren’t the solution to finding extraterrestrials, they can help refine predictions about the presence of Earth-like, water-rich exoplanets. You can read more abouthere.
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Discovermagazine.com writers rely on peer-reviewed articles and sources of high quality for their articles. Our editors also review the article for accuracy, scientific standards and editing. The Astrophysical Journal is the source for this article. Evolution of Steam Worlds – Energetic Aspects (19659022) University of Michigan News. JWST discovers first exotic “steam world” shrouded by water vapor.