In Situ Production of Methyl Chloride in Siple Dome and WAIS Divide Ice Cores from Antarctica. (usap-dc.org)
In 2004, Looy and her former Ph.D. advisor Henk Visscher proposed one way this might have played out, bases on fossilized abnormal plant spores found worldwide: volcanic gases — halocarbons like methyl chloride and methyl bromide — destroyed much or all of Earth's ozone layer, boosting UV - B exposure that would have affected life and potentially increased the genetic mutation rates in pollen and spores of plants worldwide. (sciencedaily.com)
Using data captured by ALMA in Chile and from the ROSINA instrument on ESA's Rosetta mission, a team of astronomers has found faint traces of the chemical compound [Freon - 40]--(CH3Cl), also known as methyl chloride and chloromethane, around both the infant star system IRAS 16293 - 2422, about 400 light - years away, and the famous comet 67P / Churyumov - Gerasimenko (67P / C - G) in our own Solar System. (sciencedaily.com)