Exoplanets May be More Hospitable to Life with Day-Night Cycle

The search for life on other planets continues. Now, scientists have discovered that exoplanets may be more likely to be hospitable to life and have liquid water than we thought.

"Planets with potential oceans could have a climate that is much more similar to Earth's than previously expected," said Jeremy Leconte, lead author of the new study, in a news release.

Scientists have long believed that exoplanets don't rotate like the Earth and, instead, always show their same side to their star. If so, then exoplanets would rotate in sync with their star so that there is always one hemisphere facing it; this means that one side of the planet would be in perpetual, cold darkness. However, it seems that exoplanets also have the potential to exhibit the same day-night cycle as Earth.

In order to better understand exoplanets, the researchers created a three-dimensional climate model to predict the effect of a given planet's atmosphere on the speed of its rotation, which results in changes to its climate. The model suggested that exoplanets should be able to maintain an atmosphere that could overcome the effect of tidal friction exerted by a star on whatever satellite is orbiting it, much like Earth does on the moon.

In fact, the scientists found that it's likely that a large number of terrestrial exoplanets should not be in a state of synchronous rotation. This means that they would have day-night cycles similar to Earth's which, in turn, may mean that they could support water.

"If we are correct, there is no permanent, cold night side on exoplanets causing water to remain trapped in a gigantic ice sheet," said Leconte. "Whether this new understanding of exoplanets' climate increases the ability of these planets to develop life remains an open question."

The findings are published in the journal Science.

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