A new study has claimed that there are many planets that have large amounts of water than previously thought. The research, however, said that rather than flowing as oceans or rivers on the surface, the water may be embedded in rocks of these planets. The study, conducted by international experts, has been published in the journal Science, took a population-level look at a group of planets that are seen around a type of star called an M-dwarf. The dwarf planets are the most commonly seen stars in our galaxy and scientists have detected many planets around them.
Rafael Luque, first author on the new paper and a postdoctoral researcher at the University of Chicago, said, "It was a surprise to see evidence for so many water worlds orbiting the most common type of star in the galaxy."
The researcher added, "It has enormous consequences for the search for habitable planets."
Such discoveries have become possible due to advances made in developing more powerful telescopes. These "eyes in the skies" capture a larger sample size that helps scientists identify demographic patterns - similar to how looking at the population of an entire town can reveal trends that are hard to see at an individual level.
The analyses using latest tools and technology had been done for individual planets, but much more rarely for the entire known population of such planets in the Milky Way galaxy. As the scientists looked at the numbers - 43 planets in all - they saw a surprising picture emerging.
The densities of a large percentage of the planets suggested that they were too light for their size to be made up of pure rock. Instead, these planets are probably something like half rock and half water, or another lighter molecule. The scientists gave the example of a bowling ball and a soccer ball - they're roughly the same size, but one is made up of much lighter material.
However, these planets are so close to their suns that any water on the surface would exist in a supercritical gaseous phase, which would enlarge their radius. "But we don't see that in the samples," explained Luque. "That suggests the water is not in the form of surface ocean."
Instead, the water could exist mixed into the rock or in pockets below the surface. Those conditions would be similar to Jupiter's moon Europa, which is thought to have liquid water underground.
"I was shocked when I saw this analysis - I and a lot of people in the field assumed these were all dry, rocky planets," said Jacob Bean, a University of Chicago exoplanet scientist. Mr Luque has joined his group to conduct further analyses.
