There is evidence that a planet around a distant star lost its atmosphere ― then gained a
second one through volcanic activity, according to scientists using NASA’s Hubble Space Telescope.
The planet, GJ 1132 b, is hypothesized to have begun as a gaseous world with a rocky core.
Starting out at several times the diameter of Earth, this so-called “sub-Neptune”
quickly lost its early hydrogen and helium atmosphere due to the intense radiation of
the young, hot star it orbits.
Then the planet was stripped down to a bare core about the size of Earth. And that’s
when things got interesting.
To the surprise of astronomers, Hubble observed an atmosphere which, according to their theory,
is a “secondary atmosphere” that is present now. Based on a combination of direct observational
evidence and inference through computer modeling, the team reports that the atmosphere consists
of molecular hydrogen, hydrogen cyanide, and methane, and also contains an aerosol haze.
Scientists think hydrogen from the original atmosphere was absorbed into the planet’s
molten magma mantle, then slowly released through volcanic processes to form a new atmosphere.
Though this hydrogen continues to escape into space, the secondary atmosphere is replenished
by volcanic gases that seep through cracks in the planet’s thin crust.
Scientists are wondering how many other planets might have started out as gas giants but became
smaller and rocky after their early atmospheres evaporated away.
Astronomers hope to use the upcoming James Webb Space Telescope’s infrared vision to
detect hot areas of volcanic activity on the planet.
GJ 1132 b might be orbiting a distant star 41 light years away, but thanks to the Hubble
Space Telescope, it just got a little bit closer.
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