It's always been one of the more interesting topics to humans, as another life form, from another planet with the same habitable atmosphere as earth, is an exciting yet scary prospect.
NASA seem to believe that two Earth-sized planets 40 lights years away could be habitable.
According to Huffington Post, an exploration using the Hubble Space Telescope found that the two planets' atmospheres were most likely not dominated by hydrogen, which often prevents life from forming.
Scientists analysed the planets, called TRAPPIST-1b and TRAPPIST-1c, observing them in near-infrared light, before a spectroscopy was used to decode the light, telling researchers how the atmosphere might be made up.
There is yet to be a full determination of the atmosphere, but due to the lack of hydrogen and helium, scientists are excited about the implications.
Early indicators of the two planets' atmospheres happened back in May, when they both crossed the face of their star within minutes of each other.
The agency's Geoff Yoder said: "These initial Hubble observations are a promising first step in learning more about these nearby worlds, whether they could be rocky like Earth, and whether they could sustain life.
"This is an exciting time for NASA and exoplanet research."
The star, a red dwarf star, which is at least 500million years old, is thought to be a lot dimmer than our sun, meaning the planets orbit around it between 20 and 100 times closer than Earth does to the sun. This means that at least one of the planets could orbit within the star's habitable zone.
Scientists now want to use the telescope to search for the kind of thinner atmospheres found surrounding Earth and Venus, with NASA's Hannah Wakeford saying: "With more data, we could perhaps detect methane or see water features in the atmospheres, which would give us estimates of the depth of the atmospheres."
This is very exciting.