There is a 99.7% chance that this exoplanet is home to extraterrestrial life

Researchers at Cambridge University's Institute of Astronomy estimate that there is a 99.7% chance that the distant planet K2-18b harbors life.

"This is the strongest evidence yet there is possibly life out there. I can realistically say that we can confirm this signal within one to two years [...] In a few decades' time, we may look back and recognize that this is when the living universe became accessible," Professor Nikku Madhusudhan, who leads the Cambridge astrophysics group, told the BBC.

"If we confirm that there is life on K2-18b, it should basically confirm that life is very common in the galaxy," said Mr. Madhusudhan. He acknowledged, however, that further research is needed. According to him, confirming this hypothesis of the presence of extraterrestrial life would be possible within the next one to two years.

K2-18b is the subject of much debate in the scientific community. It could contain water, but some experts, such as Dr. Nicolas Wogan, support the hypothesis that it could be a mini gas giant with no real surface.

To consider this discovery as definitive proof of extraterrestrial life, the scientific community requires a level of certainty close to 99.99999%.

K2-18b has a mass more than eight times that of the Earth and a diameter 2.5 times greater. It orbits a red dwarf star in just 33 days.

It is located some 700,000 billion kilometers from our planet, or 124 light-years, in the constellation Leo.

Signs of life on this exoplanet were detected thanks to the James Webb Space Telescope. Famous for its spectacular images of deep space, this $10 billion instrument was launched beyond the atmosphere in December 2021.

According to the BBC, the telescope's data revealed signs of chemical compounds long thought to be biosignatures of possible extraterrestrial life. On our planet, these gases are only produced by living organisms, mainly phytoplankton.

Mr. Madhusudhan also pointed out that the concentration of gas observed on K2-18b is "thousands of times higher than on Earth". According to him, this could be a sign that the planet is "teeming with life".

Professor Catherine Heymans told the BBC that it will be important for researchers to determine the exact" origin of this gas": "On Earth it is produced by microorganisms in the ocean, but even with perfect data we can't say for sure that this is of a biological origin on an alien world because loads of strange things happen in the Universe and we don't know what other geological activity could be happening on this planet that might produce the molecules." she explained.

Professor Oliver Shorttle also urges caution with regard to this discovery: "Everything we know about planets orbiting other stars comes from the tiny amounts of light that glance off their atmospheres. So it is an incredibly tenuous signal that we are having to read, not only for signs of life, but everything else. With K2-18b part of the scientific debate is still about the structure of the planet."