Aliens. We read about them in novels, and we watch them on fictional TV shows, but we've never actually encountered extraterrestrial life. Given the size of the universe, it's highly improbable aliens don't exist - but also given the size of the universe, it's highly improbable we'd find them anywhere close to Earth. Nonetheless, according to the BBC, scientists have found evidence that life could exist on another planet.

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Launched in 2021, the James Webb Space Telescope (JWST) is incredibly powerful, having reshaped the way we view the early stages of the universe and our knowledge of space. In this particular case, its ability to measure the physical and chemical properties of planets has been key. According to the BBC, "the Cambridge group has found that the atmosphere seems to contain the chemical signature of at least one of two molecules that are associated with life: dimethyl sulphide (DMS) and dimethyl disulphide (DMDS)."

To break this down, when light passes through a planet's atmosphere, molecules absorb specific wavelengths of this light. Scientists can use techniques like spectroscopy to figure out which wavelengths are being absorbed - that's what the chemical signature/fingerprint is - which helps to determine which molecules are present. In this case, they think those molecules (or gases) are dimethyl sulphide (DMS) and dimethyl disulphide (DMDS).

And why is this important? On Earth, DMS and DMDS are produced by different forms of microbial life.

Obviously, when we hear aliens, we immediately think of what we've seen in movies - intelligent forms of life, not bacteria. But these findings are promising, and given the amount of gas allegedly in its atmosphere, the planet could be full of life. In fact, on Earth, concentrations of these gases are around one part per billion in volume; on K2-18b, these figures seem they could be thousands of times higher.

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The planet on which these molecules were detected is called K2-18b. It's 124 light-years away - that's 1.7 quadrillion kilometres, and 3 billion times farther away than the moon! The planet certainly isn't close, but if we think in terms of the size of the universe, which is infinite, it's not too far away either (it's still part of the same galaxy).

The same researchers who made these findings also recently made observations which suggest carbon dioxide and methane may be present in K2-18b's atmosphere. The planet's mass is around 8.6 times that of Earth's, and it is 2.6 times larger.

However, as with any scientific observation, there is A LOT of work that goes into figuring out whether or not this detection can actually be validated as a discovery. Scientists first need to make sure their readings are definitely correct - they're about 99.7% sure at the moment, which seems very promising, but they'll need to be even more certain before we can confirm these findings.

Then, there's the issue of where the gases are coming from. On Earth, they are produced by forms of life. But when it comes to space, there's a lot we don't know.

There could be something else producing the gases - some kind of chemical process. Some scientists feel as though we should be more tentative when approaching this situation. Because there's so much we don't know, they feel like we shouldn't jump in head first and assume we've completed our search for extraterrestrial life - instead, we should be cautious and wait until once we've had more time to explore than planet, and have collected more data - which should hopefully be possibly with the JWST!

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Scientists have already been theorising about how life might look on this foreign planet. Some believe it has a vast ocean. This is partly due to the fact that ammonia has not yet been detected in its atmosphere, so it could have been absorbed by water.

Others suggest the surface is covered in molten rock, making life impossible. There remains much debate surrounding the subject.

Overall, this is an exciting discovery, but the search for life on other planets is far from over. This information is all very recent, so nothing is certain. Whether or not K2-18b actually contains alien life is yet to be confirmed, but scientists are definitely making progress and collecting evidence to keep us informed. For now, we'll just have to wait and see!