Water discovered for first time in atmosphere of habitable exoplanet

Katie Ramirez
October 29, 2019

Water vapor has been discovered on a "super-Earth" 110 light years away that is estimated to be twice the size of Earth and eight times its mass, the Daily Mail reported.

The study on this habitable-zone exoplanet that presents water vapor in its atmosphere was published in the journal Nature Astronomy.

K2-18b is the only planet orbiting a star outside our Solar System known to have water and temperatures that could support life. The lead researcher, Prof Giovanna Tinetti of University College London (UCL) depicted the disclosure as "mind-blowing".

"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".

K2-18b is one of hundreds of "super-Earths" - exoplanets with masses between those of Earth and Neptune - found by Kepler.

Because this study has found evidence for liquid water and hydrogen in this exoplanet's atmosphere and it lies within the habitable zone, there is a possibility that this world is habitable. Given its mass and radius, K2-18 b is not a gaseous planet, but has a high probability of having a rocky surface.

A planet's atmosphere helps determine various factors such as the presence of oceans and surface on a planet, its structure, and evolution.

And while nitrogen and methane may also be present, they remain undetectable-for now. K2-18b is likely to be more hostile as it is exposed to more high-energy radiation. The find means that liquid water could also exist on the rocky world's surface, potentially even forming a global ocean. Compounds absorb light at various wavelengths depending on their chemical makeup ans by studying the star's spectrum with algorithms scientists can analyse what's in the planet's atmosphere.

Although the precise composition of the atmosphere can not be extracted - Hubble is brilliant, but its not technically capable of determining chemical signatures like other dedicated telescopes - the authors modelled different scenarios to find the best fit possible with their data. Nasa's Tess mission is expected to detect hundreds more in coming years.

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Camera IconA handout artist's impression from ESA/Hubble shows the K2-18b super-Earth, the only super-Earth exoplanet known to host both water and temperatures that could support life.

By comparison, the percentage of water vapour in Earth's atmosphere varies between 0.2 percent above the poles, and up to four percent in the tropics.

Only K2-18b revealed the molecular signature of water, which is a vital ingredient for life on Earth.

"It is likely that this is the first of many discoveries of potentially habitable planets", said UCL astronomer Ingo Waldmann, also a co-author. Or a third option allows for a hydrogen atmosphere, a "tiny speck" of water, and high-altitude clouds or hazes that obscure the view. In 2017, a team determined that it could either be a rocky planet with an atmosphere - like Earth, but bigger - or a planet with a mostly water interior, covered in a thick shell of ice, like Enceladus or Europa.

"We're going to need more observations", she said. Through atmospheric studies, we can therefore learn about the history of the planet, investigate its habitability and, ultimately, discover signs of life.

Tsiaras and his team did it using the WFC3 instrument on the Hubble Space Telescope.

"We don't really know what it's like down there".

So instead, our best bet is to do follow-up observations with two successors to Hubble: the James Webb Space Telescope, which is due to launch into orbit in 2021 but has been repeatedly delayed, and the European Space Agency's ARIEL space telescope, scheduled to launch in 2029.

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