Planet ‘regrew’ its atmosphere after losing it

Astronomers have identified an extrasolar planet that appears to have regenerated its own atmosphere.

While there are plenty of known examples of planets that have lost their atmosphere (such as Mars), it now seems as though it is possible – on rare occasions – for a planet’s atmosphere to regenerate.

Situated 41 light years away, the catchily titled exoplanet GJ 1132 b is, at first glance, not dissimilar to the Earth as both have similar densities, atmospheric pressures and ages.

Unlike the Earth however, this intriguing world started out life as a gas giant before having its atmosphere stripped away due to a close encounter with a neighboring red dwarf star.

Scientists now believe that the resulting rocky core later managed to produce its own replacement atmosphere of molecular hydrogen, hydrogen cyanide and methane.

“It’s super exciting because we believe the atmosphere that we see now was regenerated, so it could be a secondary atmosphere,” said study co-author Raissa Estrela from NASA JPL.

“We first thought that these highly irradiated planets could be pretty boring because we believed that they lost their atmospheres. But we looked at existing observations of this planet with Hubble and said, ‘Oh no, there is an atmosphere there.'”

It is thought that the planet’s hydrogen was absorbed into the molten magma mantle and later released back into its atmosphere through volcanic processes.

“This process works early in a planet’s life, when the star is hotter,” said study lead author Mark Swain.

“Then the star cools down and the planet’s just sitting there.”

“So you’ve got this mechanism where you can cook off the atmosphere in the first 100 million years, and then things settle down. And if you can regenerate the atmosphere, maybe you can keep it.”

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