New Study Highlights Importance of Oceans for Exoplanet Habitability

Jul 21, 2014 by

Oceans are crucial for supporting Earth-like life on extrasolar planets, according to a study published in the journal Astrobiology.

Artist's concept of a cryobot in the ocean of Jupiter's moon Europa. Image credit: NASA.

Artist’s concept of a cryobot in the ocean of Jupiter’s moon Europa. Image credit: NASA.

The potential habitability of an exoplanet crucially depends on how its atmospheric and ocean circulation transports heat from warmer to cooler regions. Previous studies have concentrated on modeling the dynamics of atmospheres, while dramatically simplifying the treatment of oceans.

“We know that many exoplanets are completely uninhabitable because they are either too close or too far from their Sun. An exoplanet’s habitable zone is based on its distance from the Sun and temperatures at which it is possible for the planet to have liquid water. But until now, most habitability models have neglected the impact of oceans on climate,” explained Prof David Stevens from the University of East Anglia in Norwich, UK, who is a co-author on the study.

Prof Stevens and his colleagues created a computer simulated pattern of ocean circulation on a hypothetical ocean-covered Earth-like exoplanet.

They looked at how different planetary rotation rates would impact heat transport with the presence of oceans taken into account.

“Oceans have an immense capacity to control climate. They are beneficial because they cause the surface temperature to respond very slowly to seasonal changes in solar heating. And they help ensure that temperature swings across a planet are kept to tolerable levels,” Prof Stevens said.

“We found that heat transported by oceans would have a major impact on the temperature distribution across a planet, and would potentially allow a greater area of a planet to be habitable.

“Mars for example is in the Sun’s habitable zone, but it has no oceans – causing air temperatures to swing over a range of 100 degrees Celsius.”

“Oceans help to make a planet’s climate more stable so factoring them into climate models is vital for knowing whether the planet could develop and sustain life.”

“This new model will help us to understand what the climates of other planets might be like with more accurate detail than ever before,” Prof Stevens concluded.


Cullum J et al. The Importance of Planetary Rotation Period for Ocean Heat Transport. Astrobiology, published online July 20, 2014; doi: 10.1089/ast.2014.1171