Breakthrough looms: Signs of life on exoplanet K2‑18b

Is there life beyond Earth? A 99.7% probability is very high; however, for researchers to provide a definitive answer, they need to achieve a probability of 99.99999%. According to Prof. Nikku Madhusudhan, who is responsible for studying the atmosphere of K2-18b, this could take up to two years.

Despite the unconfirmed but very high probability of discovering extraterrestrial life, this development aligns with Lisa Kaltenegger's predictions.

This is no accident. Thanks to tools like the James Webb Space Telescope, possibilities for studying the universe have expanded, allowing scientists to target planets with a high likelihood of having conditions where life might have arisen and survived.

On the list of potential cosmic habitats, alongside planet TRAPPIST-1e, was also K2-18b. So, what exactly was found there?

The compounds that fuel scientific hopes are dimethyl sulfide and dimethyl disulfide, which on Earth are produced by bacteria and marine phytoplankton.

However, Professor Catherine Heymans from the University of Edinburgh cautions against premature excitement among the discoverers.

One assumption researchers have adopted is the correlation between life and liquid water. It's believed that the presence of liquid water alone does not guarantee life, but it's necessary for life's development and survival.

This significantly narrows down the conditions under which, according to current theories, life in space can arise. The search focuses on exoplanets located in the so-called habitable zone, the distance from a star where temperature and conditions allow for the existence of liquid water.

Exoplanets—planets located outside the Solar System—generate great excitement in science. Just 40 years ago, we knew of none, although many researchers suspected they might exist.

Doubts were dispelled by Aleksander Wolszczan, along with Dale Frail, who in 1992 announced the discovery of two planets (and possibly a third) orbiting the pulsar PSR 1257+12. This was heralded as a second Copernican revolution in astronomy.

Since then, the list of discovered exoplanets has been growing rapidly. In 2017, over 2,000 were known, and by 2024, astronomers have identified over 7,000 planets outside our stellar system. We can be sure that this number will significantly increase each year.

Between 1% and 2% of discovered exoplanets may be located in the "habitable zone," so the excitement among researchers is justified. Already, the number of planets that may deserve the name "second Earth" reaches dozens and will continue to grow. Alongside this, the chance that life exists on any of them increases.

An attempt to answer this question was presented in the 1960s by American astronomer Francis Drake, who formulated the so-called Drake Equation.

This formula considers the rate of star formation, the likelihood of planetary systems and planets conducive to life, and the evolution of life from simple to complex and, finally, intelligent forms capable of interplanetary communication.

The problem is that if we apply the Drake Equation under the most pessimistic assumptions, it suggests there could be 250,000 cosmic civilizations capable of making contact. Yet, no contact occurs.

The paradox of a statistically high probability of extraterrestrial life existing, despite the lack of evidence until recently, was aptly summarized by the Italian physicist Enrico Fermi. The famous Fermi Paradox can be distilled to the question: "Where are they?"

Many answers exist, and scientists' assumptions are often translated into understandable and compelling narratives by pop culture.

An example is Liu Cixin, author of the bestseller "The Dark Forest." The dark forest theory suggests that lack of contact is a survival strategy in a potentially hostile environment. The universe is full of intelligent life, but its representatives, being intelligent, do not advertise their existence.

This theory contradicts previous human actions. NASA has already sent into space detailed information about Earth, its inhabitants, and how to locate it in the vast universe. This knowledge—recorded on disks—is carried by the two Voyager probes and, in a shorter form, by plaques attached to the Pioneer 10 and Pioneer 11 probes.

There are also hypotheses suggesting that alien civilizations, if they exist, may be so advanced that their attempts at contact are invisible or incomprehensible to us. The Strugatsky brothers referenced this in "Roadside Picnic," proposing that alien civilizations regularly visit Earth, but the remnants of their visits are as abstract and incomprehensible to us as picnic debris is to ants.

This is the direction of research conducted by the SETI Institute, the University of California, Davis, and the Alaska Whale Foundation on communication with humpback whales. Successful attempts at interspecies communication of simple messages, confirmed in 2023, aim to lay the foundation for potential future communication with an extraterrestrial civilization.

As universe researchers analyze the geological structure and potential atmosphere composition of exoplanets, they also search for more unmistakable signals: radio communications, various emissions, changes in brightness, and unexplainable disturbances in the motion of planets or the brightness of distant stars.

For now—despite decades of efforts, ambitious programs like SETI, or registering unexplainable signals like the WOW Signal—no definitive success has been achieved.

The discovery of life on K2-18b could indeed be groundbreaking. It might be, because—it's worth remembering—researchers' integrity prevents them from making definitive statements, and the obtained results still require confirmation. We still have to wait to change the message about "high probability" to the unequivocal statement "we have discovered life beyond Earth."