The search for life beyond our Earth has long captured the collective imagination. Recently, a major breakthrough has been made in this area. Astronomers and astrobiologists who focus their research on exoplanets that are likely to harbor liquid oceans have made a surprising discovery.
Seventeen discovered exoplanets could host subsurface oceans hidden beneath thick layers of ice, according to a new NASA analysis. These worlds, similar to Jupiter's icy moons, could therefore be promising places to search for biosignatures, chemical signs of life.
Although these exoplanets are similar in size to Earth, they are less dense and have significantly lower surface temperatures. Lynnae Quick of NASA's Goddard Space Flight Center says these worlds could have ice-covered surfaces but receive enough internal heat from the decay of radioactive elements and the tidal forces of their stars to maintain internal oceans.
These planets' internal processes, such as gravitational interaction with their star, could generate enough heat to support a subsurface ocean. In addition, the radioactive decay of heavy elements in the planet's core could generate its own heat.
The study suggests that these planets could also experience cryovolcanic eruptions reminiscent of ice volcanoes. Inspired by geyser activity observed on two of Jupiter's moons, Europa and Enceladus, the study identifies Proxima Centauri b (closest to Earth) and LHS 1140 b as particularly promising candidates with potentially near-surface oceans and geyser activity that may exceed that of Europe.
Further observations of these worlds could include detecting the emission spectra of the light that passes through their atmospheres, potentially providing clues to the possibility of life in the cold, dark depths of these worlds.
These results were published in October in the Astrophysical Journal. They open up fascinating perspectives on the possibility of finding life forms in extreme conditions far from our blue planet and highlight human ingenuity in finding our place in the universe.