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An illustration of K2-18B, an exoplanet that is a top-class candidate “water world”. | Credit: ESA/Hubble, M. Kornmesser
According to a new study, sub-neptune planets, which are often charged as “water worlds” as possible, can be more deserts than deep sea.
Scientists thought for years, these planets, which are larger than the earth, but smaller than Neptune, could form far from their stars and pick up ice beyond the so -called “snow line”. When the planets wandered inwards, scientists thought that ice could melt into oceans that are hidden under hydrogen sky. Such hypothetical worlds were called “Hycean planets“A mixture of” hydrogen “and” ocean “.
“Our calculations show that this scenario is not possible” opinion.
The results come just a few months after top-class claims via K2-18b, an exoplanet about 124 light years away. made global headlines As a likely ocean world “swimming before life“A team of scientists who examined James Webb Space Telescope (JWST) Boastings had referred to K2-18b reports on a possible biomark gas, dimethyl sulfide-and the speculation should be used in a hydrogen-rich atmosphere over a large global ocean that could potentially support life (as we do know).
But these claims were quickly met with pushback. Independent Analyzes The same JWST data indicated the evidence of the team for DMS at best was weakWhile other experts were before that sub-neptunes are not marine worlds at all, but also rather Fleeting planets that are wrapped in thick, enemy atmospheres.
In the new study, thorn and her team modeled how the sub-neptune develops in their early life when they are covered by hydrogen gas and are covered by molten rock millions. In contrast to previous studies, the researchers included chemical interactions between the magma and the atmosphere.
Of the 248 model planets that the team examined: “There are no distant worlds with massive water layers in which water has made around 50 percent of the planet of the planet, as previously assumed,” said Dorn in the explanation. “Hycean worlds with 10-90 percent water are therefore very unlikely.”
The team found that hydrogen and oxygen – the building blocks of H2O – tend to tie themselves with metals and silicates in the interior and effectively seed water deep in the interior. Even planets that started with plenty of ice cream had less than 1.5% of their mass than water near the surface, reports the new study, far less than the ten percent that are intended for Hycean planets.
“We concentrate on the most important trends and can clearly see in the simulations that the planets have much less water than originally accumulated,” said Aaron Werlen, a researcher in Dorn’s team at ETH Zurich, who headed the new study together. “The water that actually stays on the surface because H2O is limited to a few percent.”
The researchers also found that the most water -rich atmospheres did not appear on planets that were formed far from their stars, where ice is plentiful, but on planets that were shaped in more detail in these cases.
The effects are sober for astrobiology. If there are no Hycean planets, the most promising ports for liquid water and possibly life can be on smaller, rocky worlds that are more similar to the earth.
Nevertheless, K2-18B remains a captivating goal, say scientists. As a sub-neptune, a kind of planet is missing, which is missing in our own solar system in its own solar system often in the entire galaxyIt could be basic insights into the formation of planetary systems and why ours result in as it turned out.
The new results also suggest that the earth may not be exceptional, with many distant worlds being veiled in similarly modest traces of water.
“The earth may not be as extraordinary as we think,” said Dorn in the explanation. “At least in our study it seems to be a typical planet.”
The Research was published on September 18 in the Astrophysical Journal Letters.
