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  • Writer's pictureScience & Environment

Have we found life elsewhere in the Universe?

Hints of life have been discovered by NASA on exoplanet K2-18b

By Georgie Burns

Photo Credit: An illustration, based on scientific data, of K2-18 by NASA, ESA, CSA and Joseph Olmsted (STScI)

From within the constellation Leo, over 120 light years away, the James Webb Space Telescope has discovered chemical markers on exoplanet K2-18b, which are indicative of life.

This faraway world has previously been a point of interest within the astronomy community for quite some time. It has long been established that the exoplanet receives roughly the same amount of starlight as we do on Earth from the sun, opening up the possibility the two globes share similar conditions. Already fueled by this discovery, excitement between astronomers began to build in 2019 when the Hubble Space Telescope detected signs of water vapour as K2-18b was in a ‘habitable zone’ - zones in the universe where liquid water can remain on a planet's surface. Consequently, it is thought that the exoplanet either has large oceans spanning the surface or is entirely oceanic.

Why is this discovery so important? It is an essential ingredient for life.

Until September, however, any life on this exoplanet was far less than a remote possibility as belonging to the habitable zone is not similar to having proof of life. Now, carbon dioxide, methane and potential dimethyl sulphide have been recorded in the exoplanet’s atmosphere by the James Webb Space Telescope. These chemical markers, when considered with the previous discoveries about K2-18b, are causing a swell of excitement throughout NASA and the broader space community to emerge again.

Firstly, methane and carbon dioxide support the ongoing theory of large oceans (although it is essential to note they are not definitive proof). Secondly, and perhaps more importantly, the only way we know dimethyl sulphide can be produced is by algae here on Earth. In other words, these chemicals could be a signature of organisms living on K2-18b.

Before we definitively state the existence of life on this exoplanet, much more research will be required. Identifying an atmosphere's composition involves tracking how much light is absorbed by its components, as different chemical compounds absorb specific wavelengths. However, this relies mainly on subjective assessment and is known to be a flawed process at times. There have been suggestions of extraterrestrial life before due to atmosphere composition. For example, life on Venus due to phosphine was thought possible in 2020, and the existence of Martians was considered in 2004 due to methane. However, these claims were later refuted as evidence. Accordingly, NASA has warned us to be cautious about conclusions tied to these results until more data is collected. While this is exciting news, they are adamant these results are not to be seen as direct evidence of life.

The data from K2-18b might not answer the all-important question: is there life elsewhere in the universe? However, hope remains that it is. Now the centre of its own NASA webpage, this question has been the centre of debate for centuries.

The page describes the possibility of life ‘beneath the Martian surface’ or ‘in the dark, subsurface oceans of Jupiter’s moons’.

It explains many complexities in answering the questions of extraterrestrial life, including the methods they use to hunt down any signs of life and even how future discoveries may change our definition of life. But to summarise, while the data they collect, hypotheses they suggest and missions they launch create grand images in our heads of our possible green neighbours, the overriding message is, currently, we don’t know.

Exoplanet K2-18b could be the first home of extraterrestrial life we have found. If not, though, our universe is likely home to trillions of exoplanets, any of which could house some form of life. Searching them all might take a while; however, NASA is most certainly looking.

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