Researchers have found that exoplanets, or planets outside our solar system, may contain significantly more water than previously believed. This could have major implications for the search for habitable worlds and the understanding of planetary formation and evolution.
Rethinking Planet Composition
Exoplanets have been modeled for decades as an iron core with a silicate mantle, topped by surface oceans or atmospheres resembling Earth.
The idea that planets existed — that they orbited stars, for example — was captured well in the 1902 science fiction movie A Trip to Mars. But new findings have revealed them to be far richer than this simple notion. These exoplanets are often found in a closer proximity to their stars, and thus originating hot worlds with oceans of molten magma rather that solid mantles.
It is vital, because how water acts in these magma oceans is very different While carbon dioxide is easily released into the atmosphere, water dissolves easily in its low density liquid form through molten mantle. And as the iron core grows it drags the water down with tiny drops of iron which then get assimilated in the core.
The Role of Pressure
The new research thus indicates that the higher the pressure inside a planet, the greater amount of water is dragged into the core along with iron.
Indeed iron can take up to 70 times as much water under certain conditions compared to silicates. As it is so high pressures in the core, this water exists not as molecules of H2O, but rather separate hydrogen and oxygen.
This has profound implications for the way we interpret our exoplanet data. That means without these water world delivery systems, we might be dramatically underestimating how much of what that has shaped Earth took place on other worlds — by as much as a factor of 10. Far More Watery Planets Than We Thought
Conclusion
The new research changes all that, with implications for how water is distributed on exoplanets. Instead of wide surface oceans, most of the water on a planet could be frozen solid in its bowels. This potentially means that so called ‘water world’ exoplanets could even support Earth-like habitable conditions. The findings also have broad significance in terms of interpreting observational data of exoplanets and understanding the formation and evolution of planetary systems. All in all, this is a big step forward in helping to solve one of the mysteries of exoplanets.
