Massive Exoplanet Could Be a Water World

In a recent study using NASA’s James Webb Space Telescope, scientists looked at a distant planet called K2-18b. This exoplanet is much bigger than Earth and about 8.6 times heavier. What they found were some interesting molecules: methane and carbon dioxide, which have carbon in them.

This discovery by Webb’s powerful telescope adds to what we’ve been learning lately. It leads us to think that K2-18b might be a special kind of planet called a Hycean exoplanet. These planets could have substantial amounts of hydrogen in the air and a surface covered by a water ocean.

K2-18b is a planet that orbits around a small and somewhat cooler star called K2-18. It’s in a zone where the temperature might be just right for things to live, and it’s quite far away, about 120 light-years from Earth in the Leo constellation.

Now, what makes K2-18b interesting is its size. It’s not as big as Neptune but not as small as Earth either. Rather, it is medium-sized. We don’t have anything like it in our own solar system, according to experts.

K2-18b exoplanet is actually a ‘sub-Neptune’

These kinds of planets, which are smaller than Neptune but bigger than Earth, are a mystery for scientists. They’re called ‘sub-Neptunes,’ and we don’t know a lot about them, according to Science Daily.

The James Webb Space Telescope found traces of carbon dioxide and methane in the atmosphere of the exoplanet K2-18 b. The planet is located 120 light-years away from Earth and is 8.6 times more massive than Earth. The findings suggest that K2-18 b may have a water ocean beneath… pic.twitter.com/K870RnXTLQ

— Space Tracker 🌌 (@thespacetrackr) September 12, 2023

The idea that K2-18 b, a sub-Neptune, could be a Hycean planet is quite intriguing. Some scientists believe that these kinds of planets might be great places to look for signs of life on other planets.

Nikku Madhusudhan, an astronomer from the University of Cambridge who led the study, said that our discovery shows how important it is to think about all kinds of places where life could exist when we search for it on other planets.

Usually, we focus on smaller rocky planets, but these big Hycean worlds are even better for studying their atmospheres, Madhusudhan clarified.

Ocean of water under a hydrogen-filled atmosphere

The fact that there’s a lot of methane and carbon dioxide on K2-18b and not much ammonia suggests that there might be an ocean of water under a hydrogen-filled atmosphere.

Furthermore, when Webb looked at the planet, it might have found a molecule called dimethyl sulfide, or DMS for short. On Earth, DMS is made by living things. Most of the DMS in our own air comes from tiny plants in the oceans called phytoplankton, explained Science Daily.

This new discovery is causing scientists to wonder if there might be life on K2-18b, similar to the way phytoplankton make DMS here on Earth.