Future telescopes on Earth and in space should help uncover more Super Earths orbiting red dwarf stars - believed to be the most common planets and stars in our Milky Way galaxy. K2-18 b orbits a red dwarf star in the "habitable zone" - the range of distances where liquid water could be stable on a world's surface. But that same absorption quality makes water relatively easy to pick out in another planet's atmosphere, compared to other molecules such as carbon dioxide.
Now we have for the first time managed to detect water vapour in the atmosphere of an exoplanet that is potentially habitable.
Sitting in its solar system's habitable region, aka the Goldilock's Zone, K2-18b is thought to have a temperature of between -73 and 46 degrees Celsius. Over 4000 exoplanets have been detected but we don't know much about their composition and nature.
Scientists have detected water vapor in the atmosphere of a "super-Earth" exoplanet with potentially habitable temperatures. So, month after month, the researchers waited with Hubble to capture the moment of transit. As the planet transits, "part of the stellar light is filtered through the atmosphere of the planet", Tsiaras said. This puts K2-18 b near the upper limit of what we call a super-Earth - which typically refers to planets between about one and 10 Earth masses. That atmospheric water could be a sign of liquid water on the surface (which could perhaps be covered completely by an ocean), but that's unclear for now.
"To our great surprise we saw a pretty strong signature of water vapour", said Giovanna Tinetti, a member of the UCL team. So, while the team knows there's water in the atmosphere, its abundance remains unknown. The researchers determined some of the chemicals in their atmosphere by studying the changes to the starlight as the planets orbited their suns.
"Are they more like Earth and the other terrestrial planets, or more like Uranus and Neptune, the solar system's ice giants?"
K2-18b, which was discovered in 2015, lies 110 light years away from us in the constellation of Leo. Getting to know K2-18b a bit better, she said, "will be important for understanding the potential habitability of smaller "Earth-sized" planets".
At the moment, the study of exoplanets atmospheres is limited, as this kind of measurement requires very high precision, which current instruments were not built to deliver.
Still, it's rare to glimpse evidence of water in another planet's atmosphere, and that alone should help spark enough interest in keeping these types of studies going when the next decade's technologies go online. Initially, they ran K2-18b atmosphere models with a range of atmospheric molecules that could produce absorption lines, including water (H2O), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and ammonia (NH3).
Whether or not life could exist on K2-18b is unknown, but the discovery of water vapor makes it a promising target for future observations-especially for the James Webb Telescope (JWST), which is now scheduled for launch in 2021 and will be able to detect "biosignatures"-and is possibly an indication that life is present".
"These are, statistically, equally likely, given the data", Ingo Waldmann, one of the authors of this new study, said in the news conference. "It's very hard to observe an atmosphere with water through an atmosphere with water", Waldmann, who's also based at UCL, said about trying to observe K2-18 b through Earth's atmosphere.
"The search for habitable planets, it's very exciting, but it's here to always remind us that this (Earth) is our only home and it's probably out of the question if we will be able to travel to other planets". "Given that the star is much cooler than the Sun, in the end, the planet is receiving similar radiation to the Earth", said Tsiaras. What's it made of? There's still a chance it could be bathed in a huge ocean, though, which would be more suitable for life, Abel Mendez, director of the Planetary Habitability Laboratory at the University of Puerto Rico, who was not involved in either study, told Daniel Oberhaus at WIRED.