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A planet relatively close to Earth may be the first discovered with a potentially life-sustaining liquid ocean outside our solar system, according to scientists using the James Webb Space Telescope.

More than 5,000 planets outside the solar system have been discovered so far, but only a handful are in what’s called the “Goldilocks zone”—neither too hot nor too cold—which can host liquid water, a key ingredient for life.

The exoplanet LHS 1140 b is one of the few in this habitable zone and has been closely studied since it was first discovered in 2017.

It lies 48 light-years from Earth, which equates to more than 450 trillion kilometers (280 trillion miles)—relatively close in the vast distances of space.

The exoplanet was thought to be a small gas giant called a “mini-Neptune” with an atmosphere too dense of hydrogen and helium to support extraterrestrial life.

However, new observations from the Webb telescope have confirmed that the exoplanet is in fact a rocky “super-Earth”.

It is 1.7 times the size of Earth but has 5.6 times its mass, according to a study published late Wednesday in The Astrophysical Journal Letters.

The ‘best bet’ for the ocean world

The Webb telescope was able to analyze the planet’s atmosphere as it passed in front of its star.

There was no sign of hydrogen or helium, ruling out the planet being a mini-Neptune.

The planet’s density shows that it “actually has large amounts of water,” study co-author Martin Turbet of France’s CNRS research center told AFP.

It can be a really huge amount of water.

All the water in the Earth’s oceans is only 0.02 percent of its mass. But 10 to 20 percent of the exoplanet’s mass is estimated to be water.

Whether this water is in liquid or icy form depends on the planet’s atmosphere.

“We have no direct evidence that there is an atmosphere, but several elements point in that direction,” Turbet said.

Lead study author Charles Cadillo, a PhD student at the University of Montreal, said that “of all known temperate exoplanets, LHS 1140 b may be our best bet to one day indirectly confirm liquid water on the surface of an alien world.”

One positive is that the planet is slightly warmed by its red dwarf star, which is one-fifth the size of the Sun.

The exoplanet’s surface temperature should be quite similar to that of Earth and Mars, Turbet said.

The presence of gases such as carbon dioxide will play a key role in determining whether the planet is covered in ice or water.

Bull’s eye ocean

One possibility is that the surface is mostly ice but has a vast liquid ocean where the planet is most exposed to the heat of its star.

This ocean could be about 4,000 kilometers in diameter, about half the surface area of ​​the Atlantic Ocean, the modeling suggests.

Or liquid water may be hidden under a thick shell of ice, as on the moons Ganymede, Enceladus, or Europa orbiting Jupiter and Saturn.

Webb’s instrument spotted signs that suggested “the presence of nitrogen,” Cadieux said, adding that more research is needed to confirm the finding.

Nitrogen is found everywhere on Earth and is thought to be another potential ingredient for life.

The researchers hope to get a few more hours of precious Webb telescope time to learn more about LHS 1140 b.

It will take at least a year to confirm whether the exoplanet has an atmosphere, and another two or three to detect the presence of carbon dioxide, the researchers estimated.

© 2024 AFP