Scientists have characterized the atmospheres of two planets in the Milky Way and determined both could be covered with clouds, according to NASA.
The discovery wouldn't have happened without some help from NASA's Hubble Space Telescope.
The planets include GJ 436b and GJ 1214b, which are located 36 light-years from Earth in the constellation Leo, and 40 light-years away in the constellation Ophiuchus, respectively, according to NASA.
Up until now, the "nature of the atmospheres" adjacent to each planet has prevented scientists from characterizing them. Researchers said this week that their work is a key milestone towards finding habitable planets, similar to Earth, throughout the solar system.
The study has been published in the Jan. 2 issue of the journal Nature, according to NASA.
"The two planets fall in the middle range in mass, between smaller, rockier planets such as Earth and larger gas giants such as Jupiter," said NASA in a statement. "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."
Both planets have been seen moving in front of their parent stars, also known as transiting.
At least one of the published papers in Nature discusses transit observations made by using Hubble, according to NASA. The study was led by Heather Knutson of the California Institute of Technology in Pasadena, Calif.
"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," said Knutson in a statement. "Instead of hydrogen, it could have relatively large amounts of heavier molecules such as water vapor, carbon monoxide, and carbon dioxide, which would compress the atmosphere and make it hard for us to detect any chemical signatures."
Similar observations had previously been obtained for GJ 1214b, which revealed GJ 1214b's atmosphere was "dominated" by water vapor or hydrogen, and contained high-altitude clouds.
"Both planets are telling us something about the diversity of planet types that occur outside of our own solar system; in this case we are discovering we may not know them as well as we thought," said Knutson. "We'd really like to determine the size at which these planets transition from looking like mini-gas giants to something more like a water world or a rocky, scaled-up version of the Earth. Both of these observations are fundamentally trying to answer that question."
A team of astronomers, led by Laura Kreidberg and Jacob Bean from the University of Chicago, studied the planet more closely, and they found what's been considered decisive proof that high clouds cover the planet.
Hubble also helped show that there were no chemical fingerprints in GJ 1214b's and GJ 436b's atmosphere.
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