Rocky exoplanets have long been a subject of fascination for astronomers and researchers alike, with their potential to hold secrets about the origins of our universe. Recent studies suggest that these rocky planets could contain abundant water in their molten cores, challenging our previous assumptions about water worlds and opening up new possibilities for habitability beyond our solar system.
One of the key findings from this research is the revelation that as much as 95% of an exoplanet’s water could be trapped deep inside its iron core. This discovery has significant implications for our understanding of planetary formation and the potential for life to exist on these distant worlds. Caroline Dorn, a professor of exoplanets at ETH Zurich in Switzerland, emphasized the importance of this discovery, stating that “planets are much more water-abundant than previously assumed.”
The process by which water is drawn into an exoplanet’s core begins during the planet’s formation. As rocky planets accrete rubble and experience collisions with other protoplanets, they become so hot that their entire surface is covered in a vast ocean of molten rock. Over time, this magma cools to form a silicate-rich mantle and a solid crust, with a deep core of molten iron forming beneath. Water, one of the materials present during the planet’s early stages, becomes dissolved in the magma ocean.
Previous research has shown that young planets similar in size and mass to Earth have the ability to draw this dissolved water down toward their core as the planet evolves. In fact, studies have indicated that Earth itself contains significantly more water in its interior than it does on the surface in the form of oceans. This phenomenon sheds light on the complex processes involved in planetary formation and the distribution of water within rocky bodies.
While planets like Earth are able to draw water into their cores due to their moderate internal pressures and temperatures, the same process was not clearly understood for larger rocky exoplanets known as super-earths. These super-earths, which can have masses up to 10 times that of Earth, present more extreme internal conditions that raise questions about their ability to retain water within their cores.
Using computer modeling to simulate the interactions between water and molten magma on a young rocky planet’s surface, researchers have now answered this question. The results indicate that even on super-earths, a significant portion of the planet’s water can end up in its interior, integrated with the iron droplets sinking toward the core. This process highlights the unique properties of water and its ability to interact with planetary materials under varying conditions.
The presence of water in a planet’s core has important implications for its habitability and potential to support life. While the water trapped in the core may not be accessible to surface-dwelling organisms, it could play a crucial role in shaping the planet’s overall environment. By studying the mass and radius of exoplanets, scientists can infer the density of these worlds and estimate the amount of water they contain.
It was previously assumed that water on exoplanets existed primarily on the surface in the form of deep oceans. However, the new research suggests that most of the water could be inside the planet, challenging our understanding of water worlds and their potential habitability. The presence of water in a planet’s atmosphere could provide clues about the interactions between the magma ocean in its interior and the outer environment.
One particular exoplanet of interest in this research is TOI-270d, which orbits a red dwarf star 73 light-years from Earth and has a mass nearly five times that of our planet. Studies of its atmosphere using the James Webb Space Telescope have revealed the presence of methane, carbon dioxide, and water vapor, suggesting the existence of interactions between the planet’s interior and its atmosphere.
The concept of “Hycean” worlds, named after a combination of hydrogen and ocean, presents an intriguing avenue for further investigation. These worlds, with rich hydrogen atmospheres and potential deep oceans, could offer valuable insights into the distribution of water within rocky exoplanets and their habitability. Understanding how water seeps into a planet’s interior rather than accumulating on its surface opens up new possibilities for identifying habitable planets in the galaxy.
Overall, the study of rocky exoplanets and their potential for containing water in their molten cores represents a significant advancement in our understanding of planetary formation and habitability. By unraveling the mysteries of these distant worlds, scientists are paving the way for future discoveries that could reshape our understanding of the universe and our place within it.