Scientists know that the atmospheres of planets change over time — Mars, for example, is gradually losing its atmosphere as it evaporates into space. The examples we know of suggested this was a one-way process, where an atmosphere developed and then was subsequently lost. But now, researchers using the Hubble Space Telescope have discovered a very odd planet that seems to be re-growing its atmosphere after having lost it in the past. This is the first time such a thing has been observed.
Planet GJ 1132 b is several times the size of Earth, making it a type called a sub-Neptune, and it started out with a thick atmosphere of hydrogen and helium. But, being close to its hot, young star, this atmosphere was quickly lost and the planet was reduced to a core around the size of Earth. So far, so typical.
Where it gets weird is recent observations from Hubble which show the planet has a secondary atmosphere of hydrogen, hydrogen cyanide, methane, and ammonia. Researchers think that hydrogen from the original atmosphere was absorbed by the planet’s mantle, and is now being released once more by volcanic activity. The atmosphere seems to be replenishing itself even as hydrogen continues to be lost into space.
“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 of NASA’s Jet Propulsion Laboratory (JPL) in a statement. “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.’”
Source: Digital Trends