Life outside the solar system

Writers of so-called "hard" science fiction stories or movie scripts could have imagined it without any scents, but that's exactly how it is - on Earth, earthly affairs are going on frantically, the largest countries are waging a customs war, in the west the pope dies, in the east due to a religious holiday there is a one-day truce in the war of drones, in the south students block television and boldly march across half the continent in search of justice, and a group of researchers from Cambridge publishes a paper on traces of alien life on a planet that orbiting a red giant deep in space.

The story deals with discovery as a fringe event that can change the history of civilization but fails to develop. The world on which the trace of life was found is too far not only to travel, but even to send radio signals, scientists still want more solid proof and their discussions will last for years, and Earthlings will only continue with Earth wars, Earth autocracies and Earth hopes. Without any further plot. It's like there's nobody up there. That is, nothing. Except for a little smell of cooked radishes.

And while life in Serbia came to a standstill, and students were waging an exhausting "battle" of their lives and ours, the world media, along with some local media, reported the breaking news of the most convincing proof of the existence of life beyond Earth. A research team from the Institute of Astronomy at the University of Cambridge led by Niku Madhusudhan used detailed images from today's most powerful telescope, the James Webb Space Telescope (JWST), and discovered that a very unexpected compound is found in the atmosphere of a planet with the cryptic name K2-18b orbiting a red giant star in the habitable zone.

We are talking about the organic compound dimethyl sulfide, which, as is commonly believed, cannot be formed in any other way than in living organisms. On Earth, it usually occurs in metabolic processes in phytoplankton or seaweed, but also in some other, very organic situations, during the spoilage of beer or grain. It has a very unpleasant, almost unbearable smell that most people detect very quickly - it is the smell that occurs when cooking radishes or cabbage and asparagus.

photo: nasa

INHABITABLE WORLD

The research that used this so-called biomarker as proof of the existence of life (and the unpleasant smell) on K2-18b was published in the prestigious journal "Astrophysical Journal Letters". Have we finally found life outside the Earth at the most inconvenient time? If we are, that's how it happens - the planet where it might be is incredibly far away, as much as 124 light years. This is the distance that light or any other electromagnetic wave travels from the beginning of the 20th century until today, and there is little chance that anyone from Earth will ever come into contact with this "smelly" world in any way.

But before that, only discovery. The planet K2-18b is one of 5878 extrasolar planets discovered by various space telescopes in the past two decades, since this astonishing quest to find planets beyond stars became possible. It moves around its star in the so-called habitable zone, like the Earth around the Sun, where due to the appropriate distance, the presence of liquid water, and thus life, is possible. The planet has an unusual diameter, two and a half times larger than Earth, but smaller than Neptune, which is the rarest group of worlds discovered so far. A year on it lasts 33 Earth days, and it was also studied by the Kepler space telescope and James Webb. It caused interest when it was discovered in 2019 that there is a little water vapor on it, and then carbon dioxide.

Finally, the latest research showed the presence of dimethyl sulfide. The main problem with this compound is that it is considered "short-lived", it breaks down easily, so its presence means that something is continuously producing it. It turns out that on K2-18b, whatever it is, it produces it very intensively - there is even 20 times more of this organic gas there than on Earth.

If one imagines what a world that smells like boiled radishes looks like, the reader may wonder how astronomers could possibly detect such a compound at this distance. They certainly won't smell it. The method is well known to physicists and is called spectroscopy, where by analyzing the light coming from somewhere, it can be established what compounds the world there is made of. Namely, when light from a nearby star passes through the atmosphere of K2-18b, a part is absorbed at specific wavelengths for each chemical compound (water, methane, carbon dioxide) so that it practically leaves its fingerprint in the spectrum that can then be recorded on a telescope such as JWST.

This is how this compound was discovered, not by our most powerful telescope recording an alien yawning, but by the light slightly changing color passing through the alien's exhaled breath. Of course, there are many open questions. The first is whether JWST actually detected dimethyl sulfide. For now, it seems that it is, and the researchers state that the reliability of the detection of the so-called "three sigma", which means that they are sure that it is not something else, is even 99,7 percent. However, only when they reach all "five sigma", they will be 99,99999 percent sure of the discovery.

LONG WAITING FOR A PRESCRIPTION

Another question is whether the dimethyl sulfide, smelling bearable or not, was really caused by extraterrestrial organisms. Immediately after the publication of this paper, some researchers expressed their doubt that there is no chemical process in which this compound cannot be obtained in another way. For now, such a process is not known, but skeptics believe that it might be discovered one day, which calls the "proof of life" into question. After all, traces of this compound have already been detected in the tail of comet 67P/Churyumov-Gerasimenko.

A few years ago, for example, there was great excitement when phosphine was discovered on the planet Venus, right next to us, a compound that many consider to be proof of the existence of life. But since most researchers were later confronted with the possibility that phosphine could be formed in another way, without life, the excitement subsided in the following years.

Be that as it may, there is always the question of what to do if we really establish that we are talking about life on K2-18b. This in no way means that it is intelligent life, but if it were, we would not talk to it. Just sending a radio message to K2-18b requires it to travel 124 years, the distance it takes for light to travel at nature's fastest speed, about 300.000 kilometers per second. If we only said "bye" via radio link, we would have to wait a full 248 years for an answer from aliens, and with it maybe a recipe for boiled radishes. Very difficult communication, anyway.

When it comes to physical contact, where we would send spaceships or at least probes to a distant blue radish, K2-18b is so unfathomably far that one cannot even imagine the distance. Human civilization moves immeasurably slower than the speed of light and has no way to cross such a vast space chasm. The highest speed at which any human being has ever moved is more than 10.000 times less than the speed of light and is only 39.938 kilometers per hour, which was reached by Apollo 10 during the American missions to the moon. At this speed, when we calculate the distance, it would take as much as 3,3 million years to travel to K2-18b.

Maybe you shouldn't be disappointed. Science fiction writers, if they cannot make a good story out of this case, and with them futurologists and risk assessors, at such a distance to K2-18b, they can still see a guarantee of our safety. You never know what might pop into the mind of a lover of so many radishes. Even if they don't like radishes, an encounter with the other world can be fatal for humans, at least the way ancient peoples experienced it when they encountered European colonizers. In any case, if it turns out that life has developed so far away, on the other side of space, on a planet over there, our life here will inevitably change its meaning. It will become something else. Or at least smell different.