Latest research: The extraterrestrial life we have been eagerly seeking may very well be 124.3 light-years away.
Do you ever wonder about this question: in the vast universe, are we really alone? This is an age-old question that we can't help but ask.
In 2023, a latest research from the University of Cambridge has quietly revealed a corner of the answer. This research focuses on a planet 124.3 light-years away from Earth - K2 - 18b.
It is in the direction of Leo and is a "super-Earth" orbiting the red dwarf K2-18.
Scientists have found some surprising "clues of life" in the atmosphere of this planet. Perhaps, extraterrestrial life is not as far away as we thought.
K2-18b is not a newly discovered planet.
As early as 2015, it was first detected by NASA's Kepler telescope. It is much larger than Earth - about 8.6 times the mass and 2.6 times the radius of Earth, so it is classified as a "super-Earth".
Its host star, K2-18, is a red dwarf with a mass and radius less than half that of the Sun.
Red dwarfs emit less energy than the Sun, so their "habitable zone" - the area where liquid water may exist - is much closer than that in the solar system. And K2-18b is right in such an area.
This means that it may have temperature conditions similar to those on Earth and have liquid water, thus meeting the basic prerequisites for the existence of life.
But the "possibility of having water" alone is not enough.
Scientists are more eager to know: what secrets are hidden in its atmosphere?
In 2023, NASA's most powerful space telescope, the James Webb Space Telescope (JWST), came into play. Like a "telescopic eye" traveling through time and space, it took a first peek at the atmospheric composition of K2-18b.
Scientists conduct research through a method called transmission spectroscopy analysis.
In short, when K2-18b passes in front of its star, K2-18, the star's light passes through the planet's atmosphere and part of the light is absorbed by the atmosphere. Different gases absorb specific wavelengths of light, and scientists can analyze the hidden components in these lights just like "decoding a cipher".
The results are astonishing - scientists have detected methane, carbon dioxide and water vapor in the atmosphere of K2-18b. These three substances are already very interesting because they also exist in large quantities in the Earth's life system.
But even more exciting is that they have also discovered two extremely special compounds: dimethyl sulfide (DMS) and dimethyl disulfide (DMDS).
You may have never heard of DMS and DMDS. But if you've been to the seaside and smelled that salty, slightly fishy oceanic odor, congratulations, you've actually smelled DMS.
On Earth, these two compounds are mainly released by marine plankton and are the products of their metabolism.
So far, humans have not found any abiotic processes that can produce these substances in large quantities in the natural environment of the Earth.
So here's the question: Why are there DMS and DMDS in the atmosphere of K2-18b?
This is what makes researchers both excited and cautious, because this may be the most direct sign of "life activity" so far.
This latest research further confirms this discovery. Scientists have not only used the previous near-infrared data, but also added the mid-infrared instrument (MIRI) data from the Webb telescope, covering a broader wavelength range.
They found that:
The concentration of DMS and DMDS in the atmosphere of K2-18b has reached one part per million.
In contrast, the concentration of these two substances in the Earth's atmosphere is only one part per billion.
The difference between the two is three orders of magnitude, which means that these substances on K2-18b are not present in trace amounts, but in significant concentrations.
This doesn't necessarily mean that there are marine organisms there, but it does greatly increase the possibility of the existence of life.
The researchers directly stated, "This could be a sign of life beyond the solar system. It is also the feature closest to life activities."
Of course, scientists are not in a rush to announce the "discovery of extraterrestrial life."
They emphasize that these compounds could theoretically also be produced through non - biological chemical reactions, although there are hardly any such examples on Earth.
Therefore, the next step is to simulate and analyze the environmental conditions of K2 - 18b to see if it is possible to produce such high concentrations of DMS and DMDS without the presence of life.
In addition, the observation time of the Webb telescope is extremely precious and it can't just focus on K2 - 18b. Scientists have to wait for more observation windows to continuously accumulate evidence.
Conclusion: The "Figure in the Mirror" 124.3 Light - years Away
Seen from Earth, K2 - 18b is like a distant mirror, perhaps reflecting the appearance of life - but it's a version we've never seen before.
As you can see, scientists haven't claimed to have discovered "little green men," but they have indeed found clues that point to a certain "smell of life" that was once exclusive to Earth.
K2 - 18b may not be the answer itself, but it could be the starting point for us to find the answer.