![]() Even if such heating lasts only a few hundred million years, it could provide a richer source of energy than the free-floating planet’s own heat to keep an ocean warm, initiate complex geology and possibly develop microbial life.īut how likely is it for free-floating planets to have moons in the first place? It induced such a strong tidal heating that scientists think the Moon may have played a key role in making the early Earth habitable. When the Moon formed more than 4.4 billion years ago, it was about 15 times closer to us than it is today. Hypothetically, if a free-floating planet has a large enough moon, it could further heat the planet using tidal mechanisms, similar to our Moon and Earth. That said, life on free-floating worlds would still have to miraculously emerge using the planet’s minuscule internal energy, compared to over 99% of Earth’s energy coming from sunlight. Simulated hydrogen-rich environments in labs show that certain terrestrial microorganisms can thrive under such conditions. Getting kicked out of a star system early on does have at least one advantage: strong ultraviolet light from young stars can’t strip away hydrogen atmospheres of these planets, which helps retain heat.Ī 1999 research paper Life-sustaining planets in interstellar space? suggests that a hydrogen-rich atmosphere can not only prevent free-floating planets from losing their internal radioactive heat to space but could also keep surface temperatures warm enough to sustain Earth-like oceans. Without a star, how can these dark worlds conceivably host life as we know it? Our exploration of the solar system combined with two decades of exoplanet research tells us there are several possibilities. Planets may have been ejected out of our solar system too over 4 billion years ago, and now orbit our galaxy as dark worlds. These planets originally form around stars like any other but get kicked out of their system at some point due to gravitational effects of giant planets within. ![]() Scientists think planets that don’t orbit any star, called free-floating planets or rogue planets, can harbor life too. If sunlight, a surface and an atmosphere aren’t necessary to make a world habitable, then why confine our search for life to Earth-like worlds that orbit stars? Their liquid water isn’t due to the Sun’s heat but rather warmed by friction between parts of their interiors being tugged by their planets' gravity. We know from our own solar system that icy moons orbiting giant planets far away from the Sun - such as Europa, Ganymede and Enceladus - can have underground, habitable oceans too. Simply put: Earth-like planets are not the only places where life could form. Quite a few of these exoplanets seem to be Earth-like, where surface conditions could sustain liquid water and life as we know it.īut even as next-generation telescopes aim to detect gases on such planets indicative of life, our search for such habitable worlds remains somewhat limited. Our search for planets around other stars in our galaxy has yielded us more than 4,500 worlds.
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