In a paper presented at a US conference in Boston, they said: “This bodes well for the formation of Earth-like planets and the search for life beyond our solar system.”
They concluded that water is likely to be a major component of planets that are between two to four times the size of Earth.
They may contain up to 50 per cent water compared with the Earth’s 0.02 per cent by weight.
Lead researcher Li Zeng, of Harvard, said: “Our data indicates that about 35 per cent of all known planets which are bigger than Earth should be water-rich, but it will not be as commonly found as here on Earth.
“Their surface temperature is expected to be in the 200-500C range.
“Their surface may be shrouded in a water-vapour atmosphere, with liquid underneath.
“Moving deeper, one would expect to find high-pressure ice before we reach the solid rocky core.”
The report is based on data from the planet-hunting Kepler Space Telescope.