What is a presumed sign of life doing on a dead comet?

Scientists have discovered dimethyl sulfide (DMS), a molecule thought to have only living sources, on a cold, lifeless comet. The finding calls into question the molecule’s usefulness as a biosignature and the significance of an earlier hint of it in the atmosphere of an alien planet. “This is the first sign of an abiotic source,” says Nora Hänni, a chemist at the University of Bern who presented the discovery last week at the General Assembly of the European Geosciences Union. Tim Lichtenberg, a planetary astronomer at the University of Groningen who wasn ’t involved in the study, says the work highlights how astronomers should be cautious about presumed biosignatures. “You need to look into all sorts of abiotic sources for interesting chemical compounds.” DMS is the smell of sea air. The simple molecule is produced abundantly by tiny algae that live in the oceans. Because DMS on Earth is known to be produced only by life, astronomers studying atmospheric gases on exoplanets have considered it a strong biosignature. “The astrobiology community is trying to find the perfect biosignature to look for,” says Lena Noack, a geodynamicist of the Free University of Berlin. “DMS is now the latest.” Last year, a team of astronomers drew headlines when it claimed a possible detection of DMS in the atmosphere of K2-18b, an exoplanet 8.6 times as massi...
Source: Science of Aging Knowledge Environment - Category: Geriatrics Source Type: research