Life as we know it depends on water, and so astronomers and astrobiologists have focused their efforts on identifying exoplanets that could harbor liquid oceans. In a recent analysis, NASA has revealed that 17 exoplanets could house subsurface oceans buried beneath thick sheets of ice, making them promising places to search for biosignatures – chemical signs of life.
The Mystery of Icy Exoplanets
The exact composition of these exoplanets remains unknown, but previous studies suggest that they are significantly colder and less dense than Earth. Despite being roughly the same size as our planet, they are likely covered in ice. “Our analyses predict that these 17 worlds may have ice-covered surfaces but receive enough internal heating from the decay of radioactive elements and tidal forces from their host stars to maintain internal oceans,” said Lynnae Quick of NASA’s Goddard Space Flight Center.
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In other words, their host stars may not provide conditions warm enough to keep water in liquid form on their surfaces, but internal processes can generate heat beneath their icy exteriors. The stretching and compression of rock inside a planet due to gravitational interactions with its star can provide significant amounts of internal heat – enough to sustain a subsurface ocean. Radioactive decay of heavy elements inside a planet’s core can also produce intrinsic heat.
Cryovolcanism and Geyser Activity: Clues to Life Beneath the Ice?
Quick added, “Thanks to the amount of internal heating they experience, all planets in our study could also exhibit cryovolcanic eruptions in the form of geyser-like plumes.” The study referenced geyser activity on two of Jupiter’s moons, Europa and Enceladus, to better understand such phenomena.
The research identified two particularly promising exoplanets, Proxima Centauri b and LHS 1140 b, as potential candidates for having oceans relatively close to the surface. Quick explained, “Since our models predict that oceans could be found relatively close to the surfaces of Proxima Centauri b and LHS 1140 b, and their rate of geyser activity could exceed Europa’s by hundreds to thousands of times, telescopes are most likely to detect geological activity on these planets.”
Future observations may include astronomers capturing the emission spectra of light traveling through these planets’ atmospheres. Chemicals and molecules erupted into the atmosphere from cryovolcanic activity may hold clues as to whether life might exist in the cold dark depths of these worlds.
The Potential for Life Beyond Our Solar System
This NASA study has expanded our understanding of life beyond the solar system by discovering 17 exoplanets that could have oceans of liquid water beneath their icy shells. Such water can occasionally erupt as geysers through the icy crusts, which may be observable with telescopes.
These subsurface oceans could potentially harbor life if they also possess other necessities, such as an energy supply and elements and compounds used in biological molecules. In fact, on Earth, entire ecosystems thrive in complete darkness at the bottom of the ocean, receiving energy and nutrients from hydrothermal vents.
Overall, this new research sheds light on the possibilities of finding life elsewhere in the universe and deepens our understanding of the hidden worlds beneath the icy surfaces of exoplanets.
