Water vapor has once again been detected in the atmosphere of an exoplanet, but this time the planet evolves in the zone of habitability of its star, which makes this discovery particularly exciting. In other words, we discovered water in a potentially habitable planet!

For the first time, astronomers have detected water vapor in theatmosphere of a planet located in the "habitable zone" of thestar K2-18, a red dwarf about 110 millionlight years of us, in the Lion constellation. This planet, K2-18b, is a Super-Earth discovered in 2015 by the Kepler space telescope of the Nasa.

From data acquired by the Hubble Space TelescopeIn 2016 and 2017, two teams of researchers used improved algorithms to analyze the light filtered by the atmosphere of this planet. The results revealed the molecular signature of the water vapor as well as the presence ofhydrogen and D'helium. Scientists are convinced that others molecules are present, in particular fromnitrogen and methane, but undetectable in current observations.

For the moment, it is only a question of water vapor in the atmosphere. In the absence of more advanced meteorological models and based on the data we have, it is very difficult to know if water in the state liquid is on the surface of this planet. The calculation of the quantities of water present in the atmosphere, such as the rate of cloud cover, is impossible to make.

The best candidate for looking for signs of extraterrestrial life

Properly speaking, K2-18b is not a second Earth. Eight times more massive than our planet, the composition of its atmosphere is very different from that of the Earth. In addition, the high level of activity of her star exposes her to radiation levels that are incompatible with a terrestrial type of life. Although this planet could have both liquid water and temperatures favorable to life as we conceive of it, the chances of this planet harboring one are low, if not zero.

That said, if life is not possible on K2-18b, it is possible in the cloudswhere the water would be liquid, just as it is envisaged in the clouds of Venus and of Titanbut for other reasons. Finally, it is not excluded that a very primitive life form could have benefited from biological niches to develop there.

In the near future, astronomers expect a lot of upcoming space telescopes to be launched, including the James Webb (JWST), In 2021, and Ariel, a mission of theESA to study the atmosphere of the exoplanets, but whose launch is not planned before the end of the decade 2020. In the case of K2-18b, it will again be necessary to observe its transits with the JWST who will also be able to search forozone and methane, two markers of biological activity.


This discovery, we owe it to two teams of researchers who have each published in two different journals. The first team to report results is Björn Benneke, an astrophysicist from the University of Montreal, who was published in theAstronomical Journal. The second study was conducted under the direction of Dr. Angelos Tsiaras of Center for Space Exochemistry Data of the'University College London. It was published in the journal Nature Astronomy.

If both teams worked from the same Hubble data, it is important to note that Dr. Angelos Tsiaras' team retrieved the data, admittedly from the public domain, acquired by B. Benneke who was still in the process of analyze them. A race of speed, which is not illegal in itself, but questions the very unkind attitude of these researchers of theUniversity College London.

What you must remember

  • This is the first time that water vapor has been detected on a planet evolving in the zone of habitability of its star.
  • The chances of this planet harboring an advanced form of life are nevertheless very low.
  • Future space telescopes, such as the James-Webb and the European Ariel, will be able to characterize this atmosphere in detail.

Interested in what you just read?

Subscribe to the newsletter The daily : our latest news of the day.

It will interest you too

(TagsToTranslate) exoplanet (t) Hubble (t) atmosphere (t) telluric planet (t) zone d


Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.