Hopes Dim for Habitable ‘Hycean‘ Planets Following New Simulations
WASHINGTON – Recent simulations challenge the prevailing theory that “Hycean” planets – potentially habitable worlds covered in vast oceans - are common throughout the galaxy, casting doubt on the likelihood of finding life on exoplanets like K2-18b. The findings, published by researchers led by Dr. Chao Dorn at the University of Arizona, suggest these sub-Neptune planets are more likely to possess thick atmospheres and limited surface water, diminishing their potential for supporting life as we know it.
Just months ago, K2-18b, located 124 light-years away, generated excitement after the detection of dimethyl sulfide (DMS), a potential biomarker frequently enough associated with life on Earth. This sparked speculation about a global ocean surroundings. however, subsequent analysis revealed the DMS evidence was weak, and the new research indicates that K2-18b, and planets like it, may not be the water worlds initially envisioned.
The team modeled the early evolution of 248 sub-Neptune planets, factoring in interactions between magma and atmosphere - elements frequently enough overlooked in previous studies. The results demonstrate that none of the simulated planets developed the massive water layers previously hypothesized. Planets with 10-90% water content, characteristic of the Hycean model, were not observed. Instead, hydrogen and oxygen tend to bind with metals and silicates within the planet’s interior, effectively trapping water deep below the surface. Even planets initially rich in ice retained less than 1.5% of their mass as surface water.
“Water that really survives on the surface is only a few percent,” explained Aaron Werlen, a researcher and colleague of Dr. Dorn.
Interestingly, the simulations revealed that planets forming closer to their stars - not beyond the “snow line” where ice can condense - are more likely to develop water-rich atmospheres, formed through chemical reactions between hydrogen and oxygen from molten rock.
The implications for astrobiology are significant. If hycean planets are rare, the search for extraterrestrial life may need to refocus on smaller, rocky planets similar to earth. Despite these findings, K2-18b remains a valuable subject of study as a representative of the common sub-Neptune planet type, offering insights into planetary system formation.
“The earth may not be as famous as what we imagine,” Dr. Dorn stated. “In our simulation, he is seen as a fairly ordinary planet.”
