Waterworlds: other habitable planets likely made up of 10% water, scientists say

Are there other habitable planets?

Scientists studying the composition of planets within the so-called habitable zones around far-off stars have come up with a new description of what life’s like on those distant worlds: it’s wet.

The search for life in the universe beyond the pale blue dot of Earth has taken many twists and turns over recent years, with evidence mounting about the sheer number of exoplanets (planets outside our solar system) that in all likelihood are orbiting within the habitable, “Goldilocks zones” around other stars. Named such because they’re situated “not too close and not too far” from their respective stars, thus allowing for the distinct possibility that the liquid water essential to life as we know it may exist on its surface, habitable zone planets likely number about 40 billion in the Milky Way galaxy alone, by recent estimates. Which means, first off, that the potential for life-supporting conditions existing elsewhere are very, very good. But what else can we say about those conditions on far-flung, potentially life-promoting worlds, you may ask?

In a new study published in the journal Astronomy and Astrophysics, researchers at the University of Bern in Switzerland conclude that in a large majority of cases such habitable zone planets could very well be composed of up to 10 per cent water, an inordinate amount compared to the scene here on Planet Earth where water covers over 70 per cent of its surface but makes up only 0.2 per cent of its mass.

“The fact that many planets are water rich could have potentially very strong (and negative) consequence on the habitability of such planets,” says Dr. Yann Alibert from the National Centres for Competence in Research in Switzerland. “In fact, we already showed in other articles that if there is too much water on a planet, this may lead to an unstable climate, and an atmosphere that could be very rich in CO2.”

The results stem from computer simulations of hundreds of thousands of stars of a size about one-tenth that of the Sun and fitted with protoplanetary disks of dust and gas. The simulation showed that over time, not only would the protoplanetary materials surrounding the stars pack together to create planets, some of them would also be Earth-sized and stay within the habitable zones. But further, the research showed that in 90 per cent of the simulated cased, water would likely account for more than 10 per cent of the exoplanet’s mass.

“It could be that the presence of large amounts of water is not so bad as in the case of solar type stars, but it could also well be that it is even worse for reasons that we do not know,” said Alibert. “Whatever the effect, it is something that is important to study, and we have started working on this subject.”

Interest has grown since the discovery announced in August of this year of an exoplanet within the habitable zone surrounding red dwarf star Proxima Centauri, which happens to be the star closest to Earth (aside from the Sun, that is). At 4.2 light years away, the planet named Proxima Centauri b is now the focus of intense study, with astronomical hopes setting high that the launch of the James Webb Space Telescope in 2018 will be able to produce data on the possibility of an atmosphere surrounding Proxima Centauri b. A follow up to the Hubble Space Telescope, the James Webb is a joint project of NASA, the European Space Agency and the Canadian Space Agency.

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