In a groundbreaking discovery, NASA’s James Webb Space Telescope has potentially identified indications of extraterrestrial life on a distant exoplanet known as K2-18b, which is 8.6 times the mass of Earth.
A forthcoming study, set for publication in The Astrophysical Journal Letters, details how the James Webb telescope spotted a molecule called dimethyl sulfide (DMS), a substance exclusively generated by living organisms on Earth. In addition to DMS, the researchers also observed the presence of carbon-bearing molecules, such as methane and carbon dioxide, within the exoplanet’s atmosphere.
The researchers expressed profound astonishment at these initial findings, suggesting that K2-18b may hold the potential to provide the first-ever confirmation of extraterrestrial life.
Astronomers have long paid attention to this distant world: it is located in the zone of potential habitability and is covered with an ocean.
This is how artists depicted (see below) this planet based on the knowledge available about it. It belongs to a small and dim star in the constellation Leo, the red dwarf K2-18. It is located 120 light years from us. That is, the light coming from it takes 120 years to reach us.
K2-18, unfortunately, cannot be seen with the naked eye; it was discovered only in the early 2000s. And only in 2015 it became clear that it has planets. This illustration shows the planet K2-18 b. It is 2.6 times larger than Earth in size and 8.6 times heavier in mass.
Moreover, its average density is only 2.4 grams per cubic centimeter. For comparison: the Earth has 5.5. Therefore, this planet is considered less of a super-Earth and more of a mini-Neptune.
According to scientists, it has a solid rocky core, but it is covered with a thick mantle of real water. Partially in the form of ice, and partially in a liquid state.
In 2019, using the Hubble telescope, it was possible to determine that the atmosphere of this planet contains from 20 to 50 percent water vapor. In the Earth’s atmosphere, by the way, from 0.2 to 2.5 percent. This means that K2-18 b is an even more humid and watery world, than ours. It is considered an ocean planet.
Moreover, it is located only 21 million kilometers from its dim sun. This is almost three times closer than Mercury to our star. But since the sun there is much weaker, its little Neptune receives exactly the same amount of energy from its star as the Earth does from its own.
Thus, K2-18 b is located in the so-called potential habitable zone, that is, at the optimal distance from the star – at one that allows it to maintain liquid water, and therefore life, which we cannot yet imagine without water.
The proximity of this exoplanet to the star allows us to suspect that it revolves around it, all the time “looking” at it with one side (like the Moon around the Earth). This is called tidal capture. And then it may well be that the ocean splashes precisely on the territory of the eternal day, and on the side of the endless night there is the same endless permafrost.
And now the most interesting thing: this planet was recently observed by the famous “replacement” of Hubble – the Webb space telescope, which, we recall, operates one and a half million kilometers from Earth.
Webb “viewed” and captured K2-18 b during its passage across the star’s disk, the so-called transit. The fact is that at this moment the light of the star passes through the atmosphere of the planet and is reflected in it in different shades depending on what substances are in the atmosphere.
And Webb is able to capture these shades and thus determine the composition of the atmosphere from the spectrum. And the resulting spectrum shows that there is carbon dioxide, methane and something even more curious.
In principle, even methane is some reason to suspect that there may be life activity on the planet, because here on Earth it is actively emitted by our microscopic inhabitants.
However, it also has non-biological sources, so the presence of methane is not yet a strong enough argument in favor of extraterrestrial life. But a rather stinking colorless liquid called dimethyl sulfide is indeed a very serious argument for the habitability of K2-18 b.
At least on Earth, this substance is not produced in any way except as a result of life activity. It is mainly a product of marine phytoplankton, that is, microalgae, and is also released by bacteria in sewers and wastewater. And, according to Webb’s spectral analysis, there is one on a distant planet in the constellation Leo.
“We are slowly moving towards the point where we will be able to answer that big question as to whether we are alone in the Universe or not,” Deputy Director of the Royal Astronomical Society in London, Dr Robert Massey, told the BBC.
“I’m optimistic that we will one day find signs of life. Perhaps it will be this. Perhaps in 10 or even 50 years, we will have evidence that is so compelling that it is the best explanation.”
The research team is set to further explore K2-18b by utilizing James Webb’s MIRI (Mid-Infrared Instrument) spectrograph. Their objective is to solidify the credibility of their initial findings and delve into the environmental attributes of this remote planet in greater detail. They are optimistic about confirming these early chemical indications of life within the upcoming year.