K2-18b would not host reliable alien life

Great disappointment for scientists and enthusiasts, after the new analyzes published in The Astrophysical Journal Letters

by Lorenzo Ciotti
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K2-18b would not host reliable alien life
© Wikimedia Commons

There was great expectation, perhaps too much, and in the end the expectation was disappointed. On K2-18b, a planet located 120 light years from us, there would be no reliable traces of life.

After the discovery and the initial enthusiasm, the new analyzes carried out by Shang-Min Tsai's team at the University of California at Riverside and published in The Astrophysical Journal Letters (done through the James Webb space telescope) said any signatures of life observed were not they are reliable, therefore, nothing alien on the horizon.

Discovered five years ago was an ideal candidate to host extra terrestrial life.

Recent observations by the Webb Space Telescope, in particular those published in November 2023, had attracted attention because they had identified the presence in the atmosphere of dimethylsulfide, a molecule that on Earth is produced by oceanic phytoplankton. But there was nothing to be done, the signatures were not reliable.

K2-18b
K2-18b© Wikimedia Commons
 

K2-18b

K2-18b, is an exoplanet that orbits the red dwarf star K2-18, located approximately 111 light-years from Earth.

The planet, discovered through the Kepler space telescope, has about eight times the mass of Earth with a 33-day orbit. It lies within the star's habitable zone, making it a potential candidate for life on the planet.

In 2019, two independent research studies concluded, based on joint analysis of data provided by the Kepler, Hubble and Spitzer telescopes, that there are significant amounts of water vapor in its atmosphere.

Further studies were carried out using the Hubble Space Telescope, allowing further measurements of the planet's atmosphere. Two separate analyzes by researchers at the University of Montreal and University College London based on Hubble data were published in 2019.

K2-18b
K2-18b© Wikimedia Commons
 

Both examined the spectra of starlight passing through the planet's atmosphere during transits, finding that K2 -18 b has a hydrogen and helium atmosphere with a high concentration of water vapor, which could range from 0.01% to 12.5%, or even go up to 50%, depending on what other gaseous elements are present in the atmosphere.

As mentioned, in 2023 K2-18 b was observed with the James Webb Space Telescope, which revealed the presence of carbon-containing molecules, including methane and carbon dioxide, in its atmosphere.

The abundance of these two molecules and the scarcity of ammonia support the hypothesis that the planet may be an ocean planet with a hydrogen-rich atmosphere. Additionally, the James Webb may have also provided a possible detection of a molecule called dimethyl sulfide.

The exoplanet is expected to be studied further by the ARIEL space telescope, which will launch in 2028. The ARIEL telescope, like the James Webb, will be equipped with instruments designed to determine the composition of exoplanet atmospheres.