Most extrasolar Earths are cold, dry, and land-dominated, new research says

New computer models of more than a thousand potential terrestrial planets startlingly suggest that less than one percent would exhibit the same land-ocean dichotomy as our own pale blue dot. That’s according to a new paper presented this afternoon at the Europlanet Science Congress 2022 (EPSC) here in Granada, Spain.

The study, co-authored by the Swiss-German team of Tilman Spohn and Dennis Hoening, shows how evolution and cycles of continents and water could influence the evolution of terrestrial exoplanets, EPSC reports. The results of their models suggest that planets have about an 80 percent chance of being mostly land-covered, with nearly 20 percent likely being mostly oceanic worlds, ESPC notes. Just under one percent of the computer model results had an Earth-like distribution of land and water.

If you’re looking for a second Earth, perhaps you should expect a planet with a brownish palette and mostly covered in landmass, noted geophysicist Tilman Spohn, executive director of the International Space Science Institute in Bern, Switzerland, in his presentation.

The paper on which the oral presentation was based was submitted to the journal astrobiology and the authors note that while these planets would all be considered habitable, their fauna and flora could vary widely.

Here on Earth, rivers, oceans, rivers and lakes make up 70 percent of the surface.

“The news from this newspaper is that our planet appears to be atypical; I was surprised,” Spohn told me here in Granada.

The researchers’ models began with initial conditions that included everything they knew about the formation and evolution of our own planet’s continents. They found that continental worlds with less than 30 percent ocean are likely to dominate the galaxy. Cool deserts could settle in the inner parts of the landmasses and resemble Earth’s during the last ice age, the EPSC notes. In contrast, marine worlds with less than 20 percent land would likely be humid and warm.

And if Spohn had to guess how many truly Earth-like planets are in our galaxy?

You would only find one Earth-like planet for every 10,000 rocky planets, something of that magnitude, Spohn says.

How close could the closest true Earth analog be?

About a hundred light years, says Spohn.

Does Spohn see that intelligent life can evolve on either an ocean world or a land-dominated world?

Both of these extreme plans I’m describing may also have plate tectonics, says Spohn.

Plate tectonics is the geophysical theory that the Earth’s crust is made up of large, independently moving lithospheric plates floating on top of the Earth’s mantle. Constantly on the move, they are said to have enabled a stable climate here on earth through carbon recycling.

But although Spohn has given his model planets plate tectonics, he sees greater benefits in living on a planet that has a more balanced land-ocean composition. Therefore, he concedes that the chances of finding intelligent life on such a heavily land-dominated extrasolar Earth are probably less than then on our own planet.

But we too could end up being land-dominated. Spohn says that because Earth’s continents are continually expanding, our own planet could become more land-dominated than water-dominated in a billion years.