By Amit Malewar 20 Aug, 2024
Collected atL https://www.techexplorist.com/planets-contain-water-thought/87466/
Earth’s iron core is surrounded by a mantle of rock and water on the surface. Scientists are investigating exoplanets using this simple planet model, but Caroline Dorn from ETH Zurich suggests that planets are more complex than we thought.
Most exoplanets are near their stars. Hence, their temperature is boiling, with oceans of molten rock that haven’t cooled yet. Water dissolves very well in these magma oceans – unlike, for instance, carbon dioxide, which quickly outgasses and rises into the atmosphere.
The iron core is below this molten rock. Dorn, along with Princeton researchers, studied how water is spread between the molten rock and the iron core using physics-based models. For this, they used model calculations based on fundamental laws of physics.
Almost four years ago, a study suggested that Earth’s ocean only contains a small fraction of our planet’s water. The content of more than 80 of the Earth’s oceans could be hidden in its interior. This conclusion comes from simulations and experiments that show how water behaved when the Earth was young.
The newest findings regarding water distribution on planets will significantly affect the interpretation of data from astronomical observations. Under some circumstances, astronomers can measure the mass and size of an exoplanet with their telescopes both in space and on Earth. These computations are used to create mass-radius graphs that allow inferences about the planet’s composition. Water volume can be drastically overestimated by up to 10 times if, as has been the case so far, the solubility and distribution of water are disregarded.
Dorn said, “Planets are much more water-abundant than previously assumed.”
Water distribution is an important factor in understanding planet formation and development. Once water has submerged to the core, it is stuck there indefinitely. On the other hand, when the mantle cools, the water dissolved in its magma ocean may degas and rise to the surface.
“So if we find water in a planet’s atmosphere, there is probably a great deal more in its interior,” explains Dorn.
Webb is seeking the same. The telescope has the potential to track molecules in an exoplanet’s atmosphere. Direct measurements are only possible for the upper atmospheric composition of exoplanets. Scientists want to determine the connection between the atmosphere and the inner depths of celestial bodies.
The new data on the exoplanet TOI-270d is especially intriguing. It shows clear signs of interactions between the planet’s magma ocean and its atmosphere.
According to this new study, planets with deep water layers are likely rare. As previously thought, most of the water on Super-Earths might be trapped within the core rather than on the surface.
Based on this, scientists assumed that water-enriched planets could develop Earth-like habitable conditions. Dorn and her team believe their findings offer a new perspective on the possibility of water-rich planets that could potentially support life.
Dorn said, “The iron core takes time to develop. A large share of the iron is initially contained in the hot magma soup as droplets. The water sequestered in this soup combines with these iron droplets and sinks with them to the core. The iron droplets behave like a lift that is conveyed downwards by the water.”
“Until now, this behavior had only been known to be the case for moderate pressures of the sort that also prevail on the Earth. It was not known what happens in the case of larger planets with higher pressure interior conditions. This is one of the key results of our study. The larger the planet and the greater its mass, the more the water tends to go with the iron droplets and become integrated into the core. Under certain circumstances, iron can absorb up to 70 times more water than silicates.”
“However, owing to the enormous pressure at the core, the water no longer takes the form of H2O molecules but is present in hydrogen and oxygen.”
Journal Reference:
- Luo, H., Dorn, C. & Deng, J. The interior as the dominant water reservoir in super-Earths and sub-Neptunes. Nat Astron (2024). DOI: 10.1038/s41550-024-02347-z
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