Presence of methyl chloride around infant star may impact search for aliens

New York: In a big blow to finding signs of life on other planets, astronomers have detected faint molecular fingerprint of methyl chloride, also known as Freon-40 which was believed to be a marker of life, around an infant star system and a comet.

Methyl chloride - a chemical commonly produced by industrial and biological processes here on Earth - is one of a class of molecules known as organohalogens. 

The results published in the journal Nature Astronomy reports the first detection ever of a stable organohalogen in interstellar space.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the astronomers detected the molecule around the infant star system known as IRAS 16293-2422.

The ROSINA instrument on European Space Agency's Rosetta space probe helped the astronomers detect traces of the compound around the comet 67P/Churyumov-Gerasimenko (67P/C-G) in our own solar system.

"Finding organohalogens near these young, Sun-like stars was surprising," said lead author Edith Fayolle, a researcher with the Harvard-Smithsonian Center for Astrophysics (CfA) in the US.

"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 solar systems, including our own," Fayolle added.

The cosmic discovery of this organic compound, however, is disappointing news for astrobiologists, who previously suggested searching for methyl chloride in the atmospheres of alien worlds as a possible indicator of life.

The recent ALMA and Rosetta detections raise doubts about that proposal, however. They indicate that methyl chloride forms naturally in interstellar clouds and endures long enough to become part of a forming solar system.

IRAS 16293-2422 is a collection of several infant stars, or protostars, each about the same mass as our Sun. It is located about 400 light-years from Earth and is still surrounded by its natal cocoon of dust and gas.

The researchers also noted that abundant organohalogens around a young Sun-like analog demonstrates that the organic chemistry present in the interstellar medium involves halogens, which was previously not known.

In addition, both ALMA and Rosetta detected this molecule in similar abundance ratios. Since comets are a remnant of the formation of our solar system and retain a chemical fingerprint of that era, the new observations support the idea that a young solar system can inherit the chemical make-up of its parent star-forming cloud.