Water-worlds are common: Exoplanets may contain vast amounts of water

Water-worlds are common: Exoplanets may contain vast amounts of water
Exoplanets similar to Earth, artist concept. Credit: NASA

Scientists have shown that water is likely to be a major component of those exoplanets (planets orbiting other stars) which are between two to four times the size of Earth. It will have implications for the search of life in our Galaxy. The work is presented at the Goldschmidt Conference in Boston.

The 1992 discovery of exoplanets orbiting other stars has sparked interest in understanding the composition of these planets to determine, among other goals, whether they are suitable for the development of life. Now a new evaluation of data from the -hunting Kepler Space Telescope and the Gaia mission indicates that many of the known planets may contain as much as 50% . This is much more than the Earth's 0.02% (by weight) water content.

"It was a huge surprise to realize that there must be so many water-worlds", said lead researcher Dr. Li Zeng (Harvard University),

Scientists have found that many of the 4000 confirmed or candidate exoplanets discovered so far fall into two size categories: those with the planetary radius averaging around 1.5 that of the Earth, and those averaging around 2.5 times the radius of the Earth.

Now a group of International scientists, after analyzing the exoplanets with mass measurements and recent radius measurements from the Gaia satellite, have developed a model of their internal structure.

"We have looked at how mass relates to radius, and developed a model which might explain the relationship", said Li Zeng. The model indicates that those exoplanets which have a radius of around x1.5 Earth radius tend to be rocky planets (of typically x5 the mass of the Earth), while those with a radius of x2.5 Earth radius (with a mass around x10 that of the Earth) are probably water worlds".

"This is water, but not as commonly found here on Earth", said Li Zeng. "Their surface temperature is expected to be in the 200 to 500 degree Celsius range. Their surface may be shrouded in a water-vapor-dominated atmosphere, with a liquid water layer underneath. Moving deeper, one would expect to find this water transforms into high-pressure ices before we reaching the solid rocky core. The beauty of the model is that it explains just how composition relates to the known facts about these planets".

Li Zeng continued, "Our data indicate that about 35% of all known exoplanets which are bigger than Earth should be water-rich. These water worlds likely formed in similar ways to the giant planet cores (Jupiter, Saturn, Uranus, Neptune) which we find in our own solar system. The newly-launched TESS mission will find many more of them, with the help of ground-based spectroscopic follow-up. The next generation , the James Webb Space Telescope, will hopefully characterize the atmosphere of some of them. This is an exciting time for those interested in these remote worlds".

Professor Sara Seager, Professor of Planetary Science at Massachusetts Institute of Technology, and deputy science director of the recently-launched TESS (Transiting Exoplanet Survey Satellite) mission, which will search for exoplanets, said:

"It's amazing to think that the enigmatic intermediate-size exoplanets could be water worlds with vast amounts of water. Hopefully atmosphere observations in the future—of thick steam atmospheres—-can support or refute the new findings".

Explore further

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More information: Conference Abstract: Growth Model Interpretation of Planet Size Distribution, Goldschmidt Conference, Boston (2018).
Provided by Goldschmidt Conference
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Aug 17, 2018
This may explain the Fermi paradox. Much extraterrestrial life is marine based, and not able to communicate like us. Imagine vast worlds full of alien intelligent whales and dolphins happily dwelling in their oceans.

Aug 17, 2018
"Imagine vast words full of alien intelligent whales and dolphins happily dwelling in their oceans."
Until some rogue Star Fleet yokels come along to beam them up...

Aug 17, 2018
"There be whales here", says Scotty.

Aug 18, 2018
There is a mistaken belief that a planet that water is an indicator of life on a planet. Although water is necessary for life as we know it, there are dozens if not hundreds of other factors that must be fine tuned for life to survive. If there are other life sustaining planets among the trillions in our universe, there are not likely to be many if any. And certainly, it is unlikely that life evolved on any others, as it certainly did not evolve here.

Aug 18, 2018
Starwater is real and confirmed by ALMA. Water, water everywhere but nary a drop to drink.


Aug 18, 2018
And certainly, it is unlikely that life evolved on any others, as it certainly did not evolve here.

This seems like a profoundly silly thing to say since there's abundant evidence that evolution has occurred on earth and, in fact, is still occurring. Or did you confuse evolution with abiogenesis? If that's the case, why do you think abiogenesis can't have occurred here?

Aug 18, 2018
I blame the abundance of Internet porn for encouraging the delusion among the perpetual adolescents of the Panspermia Cult pseudo-scientific woomongering.

The headline chosen for this article is a contradiction, maybe even an oxymoron? A poorly written clickbait headline that controverts the Goldschmidt Conference abstracts that it is supposedly based upon.

Aug 18, 2018
This comment has been removed by a moderator.

Aug 18, 2018
Water-worlds are common, as are deserts. What is rare is Earth's near 50-50 land-water split. The land provides nutrients for the oceans, and the oceans provide rain for the land. Life might exist on a water-world, but it would not be abundant.

Aug 18, 2018
Not unexpected that superEarths would be volatile rich, but nice confirmation.

@Bookperson: I think you got - likely - your cult leaders claims on science wrong, life is certainly not without evolution or finetuned since it survived 4 billion years and many mass extinctions.

As zz notes, you were likely thinking of emergence of life, and that is wrong too. First we can see from the rapid emergence that it is an easy process; second, phylogenies (evolution) now goes all the the way back, and again that is not hard as per the first part of my response to you.

Nevertheless, the main hypothesis among astrobiologists is that these water worlds are sterile. Unless there is intense impact flow to the planet surface, the deep ice would lock in necessary minerals from reaching the ocean. Surface water as sure indicator for habitable zone is not a sure indicator for habitable planets.

Aug 18, 2018
Ref that the spam filter did no allow as link: "The physiology and habitat of the last universal common ancestor", Weiss et al, Nature, 2016.

Aug 20, 2018
water at 200 to 500 deg celsius? the pr on the rocky surface would be enormous

Aug 20, 2018
"And certainly, it is unlikely that life evolved on any others, as it certainly did not evolve here." Posting creationist nonsense on a science news aggregator site is an indication that someone has a need for a life.

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