Alien Life More Probable on Desert Worlds

Researchers suggest life is more likely to be found on “land planets” similar to the desert planet Arrakis depicted in the science fiction story “Dune,” rather than watery worlds like Earth.

Contrary to popular belief, alien life may not only be found on watery worlds or “aqua planets” like Earth, according to research recently published in the journal Astrobiology.

Instead, researchers suggest life is more likely to occur on “land planets” rather like the desert planet Arrakis depicted in the science fiction story Dune.

Until now, the quest for life has tended to focus on planets with plenty of water. Such planets must orbit their stars within the “Goldilocks zone,” i.e. they are not so hot that water vaporizes nor so cold that water freezes.

However, due to lack of water, land planets could still harbor life and have a larger habitable zone, because less light would be reflected by water and snow, keeping the planet warmer in colder zones, and less heat would be trapped by vaporized water in the warmer zones.

Using three-dimensional global climate models, an international team of scientists found that such a planet’s habitable zone is three times wider than that of an aqua planet, meaning it could be much closer or further from its star while remaining habitable.

“A pale blue dot is not the only model for an Earth-like habitable planet,” the researchers wrote. “The first habitable planet is more likely to be a member of the land planet class than the aqua class.”

Co-author Kevin Zahnle at NASA Ames Research Center said in a press release that such a planet would be similar to Arrakis in some ways.

“The picture of the equatorial zone being just too hot to live at is there, as well as the poles being habitable,” he explained.

“I would actually think that the poles would be a good deal wetter than in ‘Dune’—there would be more open water at the poles, maybe even small streams and lakes and such.”

The findings could alter how scientists seek habitable planets, looking for the presence of oxygen rather than water.

“These planets might not exhibit signs of water that we can see, but they would of oxygen,” Zahnle said. “Also, we’re finding that water is so ubiquitous, it cannot be regarded as a signature of a planet’s habitability.”

The results also suggest that Venus, our solar system’s hottest planet, may once have been home to life up to one billion years ago.

Zahnle said that ancient Venus would have been “very hot in the tropics, cooler and wetter at the poles. Sort of Earth-like, not a lot of carbon dioxide.”