Exoplanets may be blanketed with clouds

Scientists using NASA's Hubble Space Telescope have found that the atmospheres of two of the most common type of planets in the Milky Way galaxy may be blanketed with clouds.

The planets are GJ 436b, located 36 light-years from Earth in the constellation Leo, and GJ 1214b, 40 light-years away in the constellation Ophiuchus.

The two planets fall in the middle range in mass, between smaller, rockier planets such as Earth and larger gas giants such as Jupiter. GJ 436b is categorized as a "warm Neptune" because it is much closer to its star than frigid Neptune is to the sun. GJ 1214b is known as a "super-Earth" because of its size.

Heather Knutson of the California Institute of Technology in Pasadena, California, said that the either this planet has a high cloud layer obscuring the view, or it has a cloud-free atmosphere that is deficient in hydrogen, which would make it very unlike Neptune.

Using Hubble, astronomers led by Laura Kreidberg and Jacob Bean of the University of Chicago took a closer look at GJ 1214b. They found what they consider definitive evidence of high clouds blanketing the planet and hiding information about the composition and behavior of the lower atmosphere and surface.

The new Hubble spectra data was so precise they could rule out cloud-free compositions of water vapor, methane, nitrogen, carbon monoxide, or carbon dioxide for the first time in GJ 1214b's atmosphere.

The findings have been published in the journal Nature.