Planets Probably Need Liquid Oceans to Support Life

A research team says that, in order for a planet to host any sort of widespread life, it's gotta have oceans. Why? Because they regulate temperatures so potential lifeforms don't have the insane temperature swings we see on planets like Mars.

Using a supercomputer to model climates on all sorts of theoretical exoplanets, researchers at the University of East Anglia say that the presence of oceans is perhaps even more important than the presence of an atmosphere when it comes to supporting life (at least, the type of life we know to exist).

That's because oceans are used to transport warm air from warm regions of the planet to cool ones, which helps create a more consistent climate overall. Earth's oceans are one of the reasons why temperatures don't vary all that dramatically from day to night (relatively speaking, of course). It's another reason why we're able to survive winter on most parts of the planet—oceans keep our seasons from varying so dramatically that all life dies off from extreme cold in the winter (or extreme heat in the summer).

On Mars, meanwhile, temperatures can get up to 70 degrees Fahrenheit during the day, but can fall as low as negative 100 degrees at night.

"The climate and, hence, potential habitability of a planet crucially depends on how its atmospheric and ocean circulation transports heat from warmer to cooler regions," David Stevens, a researcher at the university, wrote in a study published in Astrobiology. "Previous studies of planetary climate have concentrated on modeling the dynamics of atmospheres, while dramatically simplifying the treatment of oceans, which neglects or misrepresents the effect of the ocean in the total heat transport."

Basically, the temperature and climate of even the most basic potentially life-supporting planet comes down to a mix of its atmosphere, distance from its star, its rotational period (the length of its days—basically how long any given part of it is facing its star), and its oceans. Then, of course, you can go adding things like forests and animals and coal power plants or what have you.

Stevens and his team tried modeling a huge number of would-be planets, but temperature swings on these theoretical planets remained too high to support life as we know it without putting an ocean on the things.

“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," he said in a statement. "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."

So far, Earth is still the only planet or moon we know of that has stable stores of liquid water on its surface. But Saturn's moon Titan has methane oceans, and right now our imaging capabilities aren't good enough to detect water outside the solar system. So, who knows—it's entirely possible that another planet is as watery as Earth.