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Starlight from 124 light years away could have answered the biggest question of all
Life on Earth has found some of the most persuasive evidence yet of life off Earth, and it has only taken four and a half billion years.
A water-covered planet 124 light years from our own could be a "hycean world teeming with life," according to researchers at Cambridge University who've been studying gases in its atmosphere that exist on Earth only as a byproduct of life.
These gases – dimethyl sulfide (DMS) and dimethyl disulphide (DMDS) – are produced on Earth by the decomposition of microbial life forms such as ocean-dwelling algae. They've been identified in the atmosphere of a planet known as K2-18b by the James Webb Space Telescope and a process known as transit spectroscopy.
A team led by Professor Nikku Madhusudhan trained the telescope on K2-18b as it passed in front of its host star, a red dwarf, and minutely analysed the differences between light arriving directly from the star and light that had first passed through K2-18b's atmosphere.
Gases can now be precisely identified by which wavelengths of light they absorb and which they let through, and to what degree. Madhusudhan's team had already confirmed the existence of methane and CO2 around K2-18b. In a second study published in The Astrophysical Journal Letters it claims to have found evidence of DMS and DMDS with a "three sigma" level of statistical significance, meaning there is only a 0.3 per cent chance the results could have occurred by chance.
Madhusudhan calls the study "a transformational moment in the search for life beyond the solar system". He says it marks the dawn of a new era of "observational astrobiology" – the James Webb telescope being an optical instrument rather than a radio telescope.
Other scientists not involved in the study have urged caution, but it follows predictions by serious figures in cosmology – including in a recent Tortoise podcast – that conclusive evidence of life beyond Earth would be found before the end of this decade.
The field has been transformed by the James Webb telescope and the Hubble space telescope before it. Between them they have offered glimpses of an unimaginably vast universe with perhaps 10,000 stars for every grain of sand on earth.
There are also many more so-called Earth-Sun systems in the Milky Way alone than previously thought. Nobel Prizes were awarded in 2019 for the discovery of the first Earth-Sun system other than our own in the 1990s. Thousands more have been discovered since.
If DMS and DMDS are proved to be reliable "biomarkers" – signs of life – transit spectroscopy could become an intensely fashionable field of research. If not, the search for extraterrestrial life, never mind intelligence, will go back to its cosmic drawing board.
For more, listen to our audio investigation, Are We Alone?, on the Tortoise app or wherever you get your podcasts
Photo credit: Cambridge University
