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Analytical Chemistry

Chloromethane detected in deep space

Discovery dashes hopes that the halocarbon is a signal for extraterrestrial life

by Bethany Halford
October 9, 2017 | A version of this story appeared in Volume 95, Issue 40

Some of the massive antennas that are part of the Atacama Large Millimeter/submillimeter Array.
Credit: ESO/C. Malin
ALMA antennae in the Chilean Andes helped spot chloromethane in space.

Because phytoplankton and other microorganisms produce chloromethane (CH3Cl), astrobiologists have postulated the halocarbon could be indicative of extraterrestrial life. But that theory may not hold up now that a team led by Edith C. Fayolle, formerly of the Harvard-Smithsonian Center for Astrophysics and now at NASA’s Jet Propulsion Laboratory, has discovered chloromethane around a forming star system and in the thin atmosphere of a comet (Nat. Astronomy 2017, DOI: 10.1038/s41550-017-0237-7). Fayolle and colleagues identified chloromethane in the gas surrounding protostar IRAS 16293–2422—the first time it’s been found in deep space—using the Atacama Large Millimeter/submillimeter Array (ALMA) to detect the compound’s unique radio spectrum. The team also detected chloromethane in the coma of comet 67P/Churyumov-Gerasimenko using the Rosetta Orbiter Spectrometer for Ion & Neutral Analysis (ROSINA) instrument on the Rosetta probe, which combines two mass spectrometers and a pressure sensor. The finding demonstrates that the halocarbon, found in similar abundance around the protostar and the comet, forms naturally in places no life exists and suggests it can stick around long enough to become part of a forming solar system. This, Fayolle says, raises the question, “How much of the comet’s organic content is directly inherited from the early stages of star formation?” A more extensive look for halocarbons around other protostars and comets will be needed to find an answer, she says.


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