(Phys.org) —A pair of researchers at Peking University in Beijing China, has extended the capabilities of an existing computer simulation that is used to study tidally locked exoplanets. In their paper published in Proceedings of the National Academy of Sciences, Yongyun Hu and Jun Yang describe the improvements they've made and also how those improvements give a new perspective on the range of possible tidally locked exoplanets that may be habitable.

Enlarge / Spatial distributions of sea-ice fraction and surface air temperature. (Left) Sea-ice fraction (unit, %); (Right) surface air temperature (unit, °C); (Upper) 355 ppmv CO2; and (Lower) 200,000 ppmv CO2. In A and B, arrows indicate wind velocity at the lowest level of the atmospheric model (990 hPa), with a length scale of 15 m s−1 . In C and D, arrows indicate ocean surface current velocity, with a length scale of 3 m s−1 . Note that the color scale for surface air temperature is not linear. The substellar point is at the equator and 180° in longtitude. Credit: PNAS, Yongyun Hu, doi: 10.1073/pnas.1315215111

Prior to this new effort, most computer models that sought to recreate the conditions that exist on exoplanets that are tidally locked (they don't spin, thus only one side ever faces their star) relied mostly on the impact of atmospheric conditions. The new enhancements include possible impacts of ocean currents.

The main goal of the upgraded model is, like many others, to allow for predicting the likelihood of life existing somewhere other than here on Earth. Tidally locked exoplanets present a challenging prospect—on one hand, the side that points towards the star is likely warm enough to support life—on the other, the cold side may be so cold that gases freeze and are lost to space preventing the evolution of an atmosphere.

To try to get a better handle on what may go on with such exoplanets, the researchers extracted parts of models that try to predict ocean behavior here on Earth. Those parts were then modified to more accurately reflect what has actually been observed, namely, smaller, colder and less feature rich worlds.

Tidally locked  generally exist close to a —they get locked because they move so close to their star. This means that the amount of heat hitting the star is much less, relatively speaking, than it would be for a planet that wasn't locked, because its star is colder. Space scientists tend to refer to such planets that might hold the potential for life as an "Eyeball Earth," because the dark side resembles a pupil.

More of the review, click image