Lynnae Quick, a planetary scientist, pondered one day, several years ago, if bodies of water existed on other planets. Beyond our solar system are other planets, or exoplanets, that maybe 'ocean worlds.'
Astronomers have discovered about 4,000 exoplanets with some having atmospheres covered in ice. They have become NASA's focus for possible life outside of earth, similar to Enceladus, Saturn's moon, and Europa, Jupiter's moon.
'Plumes of water erupt from Europa and Enceladus, so we can tell that these bodies have subsurface oceans beneath their ice shells, and they have energy that drives the plumes, which are two requirements for life as we know it,' she said. As one of NASA's planetary scientist who specializes in volcanism and ocean worlds, Quick said, 'so if we're thinking about these places as being possibly habitable, maybe bigger versions of them in other planetary systems are habitable too.'
In NASA's Goddard Space Flight Center, they began searching for planets similar to the ocean world moons, which hypothetically was possible. If such exoplanets existed, telescopes would be able to detect volcanic-like structures on their surface which could geologically be active.
Ocean Worlds
Using a mathematical analysis of exoplanets, including those in the TRAPPIST-1 system, they found that more than 25% of them were possibly 'harboring oceans beneath layers of surface ice,' like Enceladus and Europa. Quick also predicted that one day, astronomers would be able to measure heat emissions, volcanic activity, and cryovolcanoes, which spew liquid or vapor instead of lava.
However, technology today cannot see exoplanets in detail yet and are too far away. All theories are just mathematical models for now. Astronomers are hopeful for the upcoming James Webb Space Telescope and future space explorations to explore deep space for signs of life.
Aki Roberge, a NASA Goddard astrophysicist said 'future missions to look for signs of life beyond the solar system are focused on planets like ours that have a global biosphere that's so abundant it's changing the chemistry of the whole atmosphere,' Working alongside Quick, he said that even though exoplanets are far from the Sun and may have significantly colder temperatures, 'they have the features we think are required for life.'
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Heat Source
Quick and her colleagues chose 53 exoplanets that were the closest to Earth's size, assumed to be more solid than gaseous. Likely able to support water on and below the surface, they also determined how much energy these exoplanets generated and released as heat.
The first of two possible heat sources was radiogenic heat, the result of billions of years of radioactive decay from the exoplanet's mantle and crust. Next is heat produce by tidal force, or energy from gravitational attraction when one planetary object orbits another, like the relationship between the exoplanet and its stars. When the heat from this relationship generates to the planet's surface, one possible exit route is via volcanoes or cryovolcanoes.
Another pathway may be tectonics, movement of the planet's outer rocky or icy layer. Discovering how much heat exoplanets discharge can determine whether or not life can survive on them. "Forthcoming missions will give us a chance to see whether ocean moons in our solar system could support life," said Quick. 'If we find chemical signatures of life, we can try to look for similar signs at interstellar distances.' An exoplanet with temperatures that allow liquid water becomes an ocean world.
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