'Super Earth' K2-18b appears to have a large ocean and could have right conditions for life: Astronomers

The exoplanet is about 2.7 times the size of Earth and 124 light-years away from our planet


                            'Super Earth' K2-18b appears to have a large ocean and could have right conditions for life: Astronomers
Artist's impression of K2 (Amanda Smith)

A Super-Earth, 124 light-years away from our planet, could be home to an ocean world, suggests a new study. 

"A central conclusion of our study is that the planet --  K2-18b -- is potentially habitable. There is a reasonable chance that the planet hosts a large ocean underneath the atmosphere at pressures and temperatures similar to those in the Earth’s oceans," Nikku Madhusudhan from Cambridge's Institute of Astronomy leading the research told MEA WorldWide (MEAWW).

Larger than Earth and smaller than Neptune, K2-18b captured headlines last year. A study found water vapor lurking in its atmosphere, which opened doors to a possibility that large planets could support life. Until then, scientists had only considered small, Earth-size rocky exoplanets as potential candidates.  

During that time, astronomers were not convinced that K2-18b could be habitable. Because the planet is large, about 2.7 times the size of Earth, and is expected to have a thick coating of hydrogen in its atmosphere.

An atmosphere like that is bad news, as temperatures on its surface could approach 5,000 degrees Fahrenheit, according to Laura Kreidberg, from the Institute for Theory and Computation, who was not involved in the study. At high temperatures, surface water could evaporate, making big planets like K2-18b inhospitable for life.

Besides, several exoplanets have water vapor -- but that does not necessarily mean that the planet has liquid water on its surface, explains Madhusudhan.

Despite the size, the planet's hydrogen envelope is not too thick (Getty Images)

But Madhusudhan and his team wanted to dig deeper. The team learned about the planet's atmosphere by factoring in data on its mass and radius. 

They found that the size was not a barrier and the planet's hydrogen envelope is not too thick, which could allow water on the surface to exist in a liquid form. They also found traces of methane and ammonium at levels lower than expected for such an atmosphere. Whether these levels can be attributed to biological processes remains to be seen, the study adds.

Madhusudhan acknowledges that this study needs more work. "We need more and better data in the future to confirm our findings, both about the prospects for habitability and about the atmospheric composition," he adds.

The study has been published in the Astrophysical Journal Letters.

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