NASA identifies 17 exoplanets that may have oceans

In a new NASA analysis, it has been revealed that 17 of the detected exoplanets may harbor subsurface oceans hidden beneath a thick layer of ice. Similar to the icy moons of Jupiter, these worlds represent potentially promising locations for the search for biosignatures—chemical signs of life.

Although the exact composition of these worlds remains unclear, temperature estimates of their surfaces from previous studies indicate that they are significantly colder than Earth. Additionally, despite being roughly the same size as our planet, their density is lower.

"Our analysis suggests that the surface of these 17 worlds may be covered in ice, but they may receive enough internal heat from the decay of radioactive elements and tidal forces caused by their stars to maintain subsurface oceans in a liquid state," notes Lynnae Quick from NASA's Goddard Space Flight Center.

In other words, while the host stars of these planets may not provide sufficiently warm conditions to maintain water in a liquid state on their surfaces, these planets could undergo processes capable of generating heat beneath their surfaces. For instance, gravitational interactions with their stars might cause stretching and compressing of rocky materials inside the planets, providing a significant amount of internal heat to sustain subsurface oceans. The radioactive decay of heavy elements in the planet's core could also contribute to internal heat.

"Thanks to internal heating, all planets in our study could exhibit cryovolcanic eruptions in the form of geyser-like plumes," says Quick.

This study builds on what we know about the geyser activity of Jupiter's two moons—Europa and Enceladus. Two exoplanets mentioned in the study, Proxima Centauri b and LHS1140 b, stand out as particularly promising candidates for having oceans relatively close to the surface.