Water has been discovered for the first time in the atmosphere of an exoplanet with Earth-like temperatures that could support life as we know it, scientists revealed Wednesday.
Eight times the mass of Earth and twice as big, K2-18b orbits in its star’s “habitable zone” at a distance — neither too far nor too close — where water can exist in liquid form, they reported in the journal Nature Astronomy.
The National Geographic reported that K2-18b, discovered in 2015 by NASA’s Kepler spacecraft, is very unlike our home world: It’s more than eight times the mass of Earth, which means it’s either an icy giant like Neptune or a rocky world with a thick, hydrogen-rich atmosphere
“This planet is the best candidate we have outside our solar system” in the search for signs of life, co-author Giovanna Tinetti, an astronomer at University College London, told AFP.
“We cannot assume that it has oceans on the surface but it is a real possibility.”
Of the more than 4,000 exoplanets detected to date, this is the first known to combine a rocky surface and an atmosphere with water.
Most exoplanets with atmospheres are giant balls of gas, and the handful of rocky planets for which data is available seem to have no atmosphere at all.
Even if they did, most Earth-like planets are too far from their stars to have liquid water or so close that any H2O has evaporated.
Future space missions are expected to detect hundreds more in the coming decades.