Traces of dimetylsolfuro on K2-18b: possible sign of life on an oceanic exoplanet at 120 light years from the earth. The most promising discovery ever?
The secular life search In addition to the terrestrial borders, it has conducted scientists through fascinating cosmic scenarios, from Marzian methane emissions to Venusian phosphine buffs. Yet, until today, Humanity seemed to contemplate a silently empty universe. Now a team of researchers advances what you define The most convincing evidence of extraterrestrial existencenot in our planetary neighborhood, but on a giant giant planet 120 light years distant, known as K2-18Bon which the Attentions of scientists have been focused, to be honest, for some years already.
A further in -depth analysis of the atmosphere of this exoplanet suggests the abundant presence of a molecule which, on earth, has a single ascertained origin: living organisms such as seaweed.
It would be the first time
“It is no one of anyone to declare prematurely that he has discovered life,” said Nikku Madhusudhan, astronomer of the University of Cambridge and the main author of the study. However, he added that the most plausible explanation for his group’s observations is that K2-18B is wrapped in a vast warm ocean, potentially teeming with life.
“This is a crucial moment,” said Madhusudhan. «It is the First time that humanity sees potential biofrar On a planet located in the habitable area of its star ». The research, published onAstrophysical Journal Letterswas welcomed by other scientists as a first exciting step to decipher the nature of K2-18b. However, The scientific community remains cautious in drawing final conclusions.
In any case, it will take patience
“It’s not the definitive test,” said Stephen Schmidt, Johns Hopkins University Planetologist. “It is a significant clue, but we cannot yet say with certainty that the planet is habitable.”
If Extraterrestrial life should actually exist on K2-18bor elsewhere in the cosmos, its revelation will require patience. “Unless we come across an alien that greets us, the irrefutable test will take time,” said Christopher Glein, planetologist of the Southwest Research Institute of San Antonio, Texas.
The story of the exoplanet K2-18b
K2-18B was discovered in 2017 by Canadian astronomers, thanks to Observations conducted with terrestrial telescopes in Chile. Belongs to a class of planets common outside our sun system, the so -called sub -nettunowho have no similarities in our immediate vicinity. These worlds are significantly larger than the internal rocky planets, But smaller than Neptune and other external giants.
Already in 2021, Madhusudhan and his collaborators had hypothesized that sub -nettuno could be covered with warm oceans water and wrapped in atmospheres rich in hydrogen, methane and other carbon compounds. To describe these unusual planets, Coniaronor the term Hycean, A fusion of the words “hydrogen” and “ocean”.
The help of the James Webb spatial telescope
The advent of the James Webb space telescope in December 2021 offered astronomers An unprecedented tool to peel the sub -nettuno and other remote planets up close. When a exoplanet transit in front of his mother star, his atmosphere, if present, is illuminated. The gases that compose it alter The color of the stellar light that reaches the Webb telescope. By analyzing these variations in the wavelengths, scientists can deduce the chemical composition of the atmosphere.
Traces of dimetylsolfuro (which smells of sea!)
In 2023, Dr. Madhusudhan team reported weak traces of a molecule of potential importance: the Dimetylsolfuroa compound formed by sulfur, carbon and hydrogen. On earth Life is the only note of Dimetylsolfuro. In the oceans, some species of algae produce this compound, which spreads in the air contributing to the characteristic Scent of the sea. This occurs when these organisms die or are consumed by bacteria or zooplankton: in this case, the dimetylsulfonopropononate produced by algae He degrades and releases dimetylsolfuro.
Astrobiologists had already hypothesized that Dimetylsolfuro could represent a biological signature on other worlds. Last year, the Madhusudhan group had a second opportunity to look for dimetylsolfuro. While K2-18B passed again in front of his star, they used A different Webb telescope tool to analyze stellar light filtered through the atmosphere of the planet. This time, they observed an even more intense dimetylsolfuro signal, accompanied by a similar molecule, the dimetildisulfuro.
“It’s shocking,” said Madhusudhan. “We have dedicated a huge amount of time just to try to exclude the signal.”
What if it wasn’t a Hycean?
Regardless of the analysis conducted, The signal remained robust. The researchers concluded that K2-18B could actually host a significant amount of dimetylsolfuro in its atmospherethousands of times higher than the levels found on Earth. This would suggest that his Mari Hycean could be rich in life.
However, other scientists underline the need for further research. An open question concerns the actual habitability of K2-18b as a world Hycean.
Glein and his colleagues proposed that K2-18B could be a huge rock body with an ocean of magma and a dense and hot atmosphere of hydrogen, A scenario unfavorable to life as we know it.
Laboratory experiments will also be necessary to interpret the new data, for example by recreating The possible conditions on sub -nettuno planets and checking if the dimetylsolfuro behaves in a way similar to what is observed on earth.
