Astronomers have discovered a ‘waterworld with a boiling ocean’ in deep space.

Key takeaways:

1. NASA’s James Webb Space Telescope (JWST) observed a distant exoplanet, TOI-270 d, about 70 light years away, which may be entirely covered by a deep, hot ocean.
2. Researchers from the University of Cambridge detected methane, carbon dioxide, and water vapor in the planet’s atmosphere, suggesting a water-rich environment with a hydrogen-rich atmosphere.
3. The planet is likely inhospitable due to extreme conditions, with ocean temperatures potentially exceeding 100°C, and a thick, high-pressure atmosphere.
4. A Canadian team, led by Prof. Björn Benneke, argues TOI-270 d could be much hotter, possibly 4000°C, with a supercritical, dense atmosphere rather than a liquid ocean.
5. Although not yet conclusive for habitability, the findings highlight the precision of JWST in detecting atmospheric details, which could lead to future discoveries of potentially habitable worlds.

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JWST may have spotted an ocean world with steam, a boiling ocean, and super-hot temperatures!

A Possible “Occean World” with Extreme Conditions

Recent observations by NASA’s James Webb Space Telescope (JWST) have uncovered clues that a distant exoplanet, TOI-270 d, could be a “waterworld,” potentially covered by a deep, hot ocean. This intriguing find advances scientists’ quest to locate habitable worlds beyond Earth. Situated approximately 70 light years away and twice the size of Earth, TOI-270 d is a planet whose atmosphere revealed traces of water vapor, methane, and carbon dioxide—key indicators that researchers say align with a watery, hydrogen-rich environment.

The international team from the University of Cambridge, led by Professor Nikku Madhusudhan, used data from JWST to explore TOI-270 d’s atmosphere. The lack of ammonia—a compound expected in a hydrogen-rich environment but highly soluble in water—further supports the idea that the planet may possess an extensive ocean beneath its atmosphere. Madhusudhan’s analysis suggested that this ocean could reach temperatures exceeding 100°C, yet still remain in liquid form due to the planet’s high atmospheric pressure. However, he emphasized that the environment would not resemble an inviting seascape; TOI-270 d is tidally locked, meaning one side of the planet constantly faces its star, while the other remains in darkness. This setup likely results in extreme temperature differences between the sides, creating an atmosphere that could exert pressure tens to hundreds of times greater than that on Earth.

Controversy and Future Implications for Exoplanet Research

While Madhusudhan’s team describes TOI-270 d as a possible “hycean world”—a type of exoplanet with a water ocean under a hydrogen-rich atmosphere—other researchers present an alternative view. A Canadian team led by Professor Björn Benneke at the University of Montreal, which also examined the JWST data, found evidence of water vapor but questioned whether liquid water could exist at such extreme temperatures. Benneke’s group suggests that TOI-270 d could reach temperatures as high as 4000°C, which would cause water to exist in a supercritical fluid state—a state between liquid and gas where water becomes a dense, hot fluid.

Both groups also observed carbon disulfide in TOI-270 d’s atmosphere, a compound associated with biological processes on Earth. However, given that it can also form abiotically, scientists cautioned against interpreting this as evidence of life. Professor Madhusudhan noted that additional observations could clarify the water vapor’s abundance in TOI-270 d’s atmosphere, ultimately helping confirm or refute the ocean theory. Dr. Jo Barstow, an astronomer at the Open University who was not involved in the research, added that studying these planetary spectra is exciting, as JWST enables scientists to explore environmental conditions unlike any in our solar system.

These discoveries showcase the JWST’s potential to deepen understanding of exoplanets and offer hope for finding truly habitable worlds in the future. The TOI-270 d observations underscore the telescope’s ability to detect complex atmospheric compositions and prompt further exploration of the conditions that define life’s potential beyond Earth.