Hubble Spots Atmosphere Forming on Earth-Sized Exoplanet

Before you start packing your bags for GJ 1132b, be aware that, while it may be Earth sized and is forming an atmosphere, it's not going to be a nice place to visit. GJ 1132b is in very close orbit around a red dwarf, making a full orbit in a day and a half, is tidally locked, and the surface is almost certainly nothing but molten rock. And that fresh atmosphere is composed of hydrogen, hydrogen cyanide, methane, and ammonia, with a hydrocarbon haze to top things off. 

But it is interesting nonetheless because it shows that planets, even those super close to their stars, can reform an atmosphere. Scientists believe that GJ 1132b started out as a sub-Neptune, but that the initial hydrogen-helium atmosphere was lost when the planet moved in close, leaving the dense rocky core completely devoid of atmosphere. They think that the hydrogen was actually absorbed into the planet's surface and is being released by volcanism at a faster rate than the solar winds can strip away, leaving a thin atmosphere similar in pressure, if not composition, to Earth's. This is good news for finding habitable planets, because it shows that planets don't have to start out Earth-like to eventually become habitable. If these young sub-Neptunes can lose their thick atmosphere but regenerate a thinner one, they could eventually become nicer places to live once the solar system settles down. Hey, anything to boost the odds of finding a habitable exoplanet is good news.