Alas, freon-40 molecule is no evidence for life 

Alas, freon-40 molecule is no evidence for life 

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New ALMA observations reveal that the hunt for life beyond Earth is not as easy as some had hoped. 

Over the past decades, astronomers have detected more than 3,500 planets orbiting other stars than our own Sun. No one knows if there’s life on some of these planets. Astronomers might find out by studying the atmospheres of these remote worlds. Certain molecules in the atmosphere could betray the presence of living organisms. Such tell-tale molecules are known as biomarkers. 

A certain type of molecules, so-called organohalogens, were thought to be reliable biomarkers. On Earth, organohalogens are produces by organic activity. (Incidentally, they’re also produced as byproducts of industrial processes.) A well-known example of an organohalogen is freon-40. Freon-40 is a molecule that consists of one carbon atom, three hydrogen atoms and one atom of chlorine. Who knows, finding freon-40 in the atmosphere of a distant planet might betray the presence of life. 

Not so, according to new ALMA observations. Freon-40 was found around a newborn star at 400 light-years distance from the Earth. The star is so young that it can’t have planets already, let alone living organisms. Apparently, the freon-40 molecules are formed in another way. They’re not reliable biomarkers. 

Freon-40 has also been found around a comet in our own solar system. The comet, known as 67P/Churyumov-Gerasimenko, was studied in detail by the Rosetta spacecraft of the European Space Agency. There’s no life on comets, so these molecules, too, must have another origin. 

The good news is that the new findings shed some light on the origin of life. The first living organisms presumably formed in a mix of various molecules, dissolved in water. Freon-40 and similar molecules were probably part of this ‘primordial soup’. So instead of pointing to existing life, organohalogens may play an important role in the origin of life. 


Freon-40 was found in the immediate surroundings of a young protostar known as IRAS 16293-2422. This baby star was first discovered by the American-Dutch Infra-Red Astronomical Satellite (IRAS). It is part of a large star-forming region in the constellation Ophiuchus (the Serpent Bearer) known as the Rho Ophiuchi cloud, at some 400 light-years away from the Earth. ALMA was able to identify the molecule because it emits millimeter radiation at some very specific wavelengths. 


The ALMA discovery of freon-40 around IRAS 16293-2422 was made by a large international team of astronomers, led by Edith Fayolle. Edith is an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. She worked together with colleagues from Denmark, Switzerland, Germany, the United Kingdom, and Sweden. The team’s results have been published in Nature Astronomy.