A planet relatively near Earth may be the first outside our solar system to have a liquid ocean that could potentially sustain life, according to scientists using the James Webb space telescope.
More than 5,000 planets have been discovered outside the solar system so far, but only a few of them lie in the “Goldilocks zone” — neither too hot nor too cold — where liquid water, a key ingredient for life, could exist.
The exoplanet LHS 1140 b is one of the few planets in this habitable zone, and has been under intense scrutiny since it was first discovered in 2017.
It is located 48 light-years from Earth, which equates to more than 450 trillion kilometers (280 trillion miles) — relatively close in the vast distances of space.
This exoplanet was believed to be a small gas giant called a “mini-Neptune”, with an atmosphere so dense with hydrogen and helium that extraterrestrial life would be impossible to support.
However, new observations from the Webb telescope have confirmed that this exoplanet is in fact a rocky “super-Earth.”
It is 1.7 times larger than Earth but has a mass 5.6 times that of Earth, according to a study published late Wednesday in the Astrophysical Journal Letters.
Oceans ‘best bet’ for the world
The Webb telescope was able to analyze the planet’s atmosphere as it passed in front of its star.
There were no signs of hydrogen or helium, ruling out the possibility that the planet was a small Neptune.
Study co-author Martin Turbet, of France’s CNRS scientific research centre, told AFP that the planet’s density shows that “there is a really large amount of water on it.”
This could literally be a huge amount of water.
All the water in Earth’s oceans makes up only 0.02 percent of its mass. But it is estimated that 10 to 20 percent of the exoplanet’s mass is water.
Whether this water is in the form of liquid or ice depends on the planet’s atmosphere.
“We don’t have any direct evidence that it has an atmosphere, but several elements point to it,” Turbet said.
“Of all the temperate exoplanets currently known, LHS 1140b may be our best chance to one day indirectly confirm liquid water on the surface of an alien world,” said Charles Cadieux, a PhD student at the University of Montreal and lead author of the study.
One positive is that the planet slowly gains heat from its red dwarf star, which is one-fifth the size of the Sun.
Turbet said the exoplanet’s surface temperature should be roughly similar to that of Earth and Mars.
The presence of gases such as carbon dioxide will play an important role in determining whether the planet is covered with ice or water.
Bulls-Eye Ocean
One possibility is that its surface is mostly ice, but there is also a vast liquid ocean where the planet is most exposed to its star’s heat.
Modelling has shown that this ocean may be about 4,000 kilometres in diameter, about half the surface area of ​​the Atlantic Ocean.
Or liquid water may be hidden beneath a thick layer of ice, like on the moons Ganymede, Enceladus or Europa, which orbit Jupiter and Saturn.
Cadieux said Webb’s instruments detected signals that pointed to “the presence of nitrogen.” He added that more research is needed to confirm the discovery.
Nitrogen is found everywhere on Earth, and is considered another possible ingredient for life.
Researchers hope to get a few more hours of the Webb telescope’s valuable time to find out more about LHS 1140b.
Researchers estimate it will take at least a year to confirm whether the exoplanet has an atmosphere, and another two or three years to detect the presence of carbon dioxide.
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