Scientists have announced today that a stable organohalogen, a class of compounds normally produced by organisms on Earth, has been detected for the first time in space.
But discovering the faint traces of the chemical known as Freon-40 or methyl chloride (CH3Cl) or chloromethane in places that predate life has dashed hopes of it being used as marker of finding life in space.
Data taken from the Atacama Large Millimeter/submillimeter Array (ALMA) Telescope in Chile and the ROSINA instrument aboard the Rosetta orbiter revealed that organohalogens are present around a young star system, codenamed IRAS 16293-2422, 400 light years away, and the well-known comet 67P/Churyumov-Gerasimenko in our Solar System.
The results were published in Nature Astronomy on Monday.
Organohalogens contain a mixture of halogen atoms - such as chlorine or fluorine - bonded with carbon or other elements. It was once thought finding molecules of that class in space could potentially hint at extraterrestrial life because they are created by some biological processes in organisms ranging from humans to fungi. They are also used to create dyes and drugs, and once used as refrigerants before they were banned for damaging the ozone layer.
Edith Fayolle, lead author of the paper and a researcher at the Harvard-Smithsonian Center for Astrophysics at Harvard University, described finding the organohalogen around the young Sun-like stars as “surprising”.
"We simply didn't predict its formation and were surprised to find it in such significant concentrations. It's clear now that these molecules form readily in stellar nurseries, providing insights into the chemical evolution of planetary systems, including our own," she said.
Finding the molecule around stars and cold asteroids, spots where the chances of life are slim, mean organohalogens are probably not reliable chemical markers of life. Scientists studying exoplanets like to look out for a list of molecules that contain carbon, nitrogen, or oxygen - elements closely associated with biological processes or necessary for life. But establishing a concrete list remains difficult.
Although the finding shows organohalogens are not a sign of existing life, the compounds could still be important precursors to life.
Karin Öberg, co-author on the study and also a researcher at the Harvard-Smithsonian Center for Astrophysics, said: "ALMA's discovery of organohalogens in the interstellar medium also tells us something about the starting conditions for organic chemistry on planets. Such chemistry is an important step toward the origins of life. Based on our discovery, organohalogens are likely to be a constituent of the so-called 'primordial soup', both on the young Earth and on nascent rocky exoplanets."
Finding precursor sugar and amino acid molecules around stars supports that idea, as they can be spread and passed onto planets during the formation process thanks to comet impacts.
The additional discovery of Freon-40 around Comet 67P/C-G strengthens the links between the pre-biological chemistry of distant protostars and our own Solar System," Jes Jørgensen, co-author of the paper and a researcher from the Niels Bohr Institute at University of Copenhagen, Denmark, added.
"Our results shows that we still have more to learn about the formation of organohalogens," concludes Fayolle. "Additional searches for organohalogens around other protostars and comets need to be undertaken to help find the answer." ®