A team of scientists has found that several exoplanets between two and four times the size of Earth likely contain a substantial amount of water, a discovery that could have implications for the search of life in the galaxy.
The researchers made the discovery that several of the known exoplanets can contain as much as 50 percent water after analyzing data from the Kepler Space Telescope and the Gaia mission.
“It was a huge surprise to realize that there must be so many water-worlds,” lead researcher Li Zeng, PhD, of Harvard University, said in a statement.
Previously, scientists split the 4,000 confirmed or candidate exoplanets into two size categories—planets with a planetary radius around 1.5 the size of Earth’s or planets with a planetary radius around 2.5 times that of Earth.
In the new study, the scientists analyzed the exoplanets further with mass measurements and radius measurements to develop a model of their internal structure that indicates that the planets about 1.5 times the size of Earth tend to be rocky planets, while the other ones could be water worlds.
“We have looked at how mass relates to radius, and developed a model which might explain the relationship,” Zeng said. “This is water, but not as commonly found here on Earth. 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.”
The new data indicates that about 35 percent of the known exoplanets larger than Earth are water-rich.
“These water worlds likely formed in similar ways to the giant planet cores [Jupiter, Saturn, Uranus and Neptune] which we find in our own solar system,” Zeng said. “The newly-launched TESS mission will find many more of them, with the help of ground-based spectroscopic follow-up.
“The next generation space telescope, 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.”
The researchers presented their findings during the Goldschmidt Conference in Boston from August 12 to 17.