New study confirms many sub-Neptune exoplanets are unlikely to be water worlds-Here is what study says

New study confirms many sub-Neptune exoplanets are unlikely to be water worlds-Here is what study says (Image: ESA/Hubble, M. Kornmesser)

A recent study has cast doubt on the idea that many exoplanets, especially the so-called “sub-Neptunes”. These are worlds larger than Earth but smaller than Neptune, which were once thought to be covered in oceans. Although astronomers once imagined these planets as water-rich and potentially habitable, new findings suggest that is unlikely to be the case.

• Who conducted the research?

An international team of planetary scientists carried out detailed computer simulations. Their models and research examined how water might behave when interacting with both the molten interiors and atmospheres of exoplanets.

The results suggest that much of the water is not available on the surface but instead it becomes bound up in their interiors. This reduces the chances of finding global oceans. The team looked closely at exoplanets orbiting stars throughout our galaxy, including well-known candidates once thought to have seas.

• Why water matters?

In earlier research, scientists had estimated that sub-Neptunes might hold anywhere from 10% to 90% of their mass as water. This raised hopes for the possibility of vast oceans. But the new analysis shows a different picture.

The water of these exoplanets is chemically locked inside the planet’s structure, leaving little left to form surface oceans. This is similar to K2-18b, which was once thought to be a promising ocean planet, but now considered far less likely to host liquid seas.

• What comes next?

These findings hint that Earth may not be a rare outlier but instead fairly typical in how it holds its water and balance between surface, ocean and interior. This means astronomers may need to turn their attention away from giant sub-Neptunes and instead focus on smaller, rocky planets.

With upcoming advanced telescopes, the new priority will be pinpointing truly Earth-like worlds rather than chasing worlds that only appear water-rich at first glance.