Free Astronomy Magazine November-December 2017

39 NOVEMBER-DECEMBER 2017 SPACE CHRONICLES tions. It’s clear now that these mo- lecules form readily in stellar nurseries, providing insights into the chemical evolution of plane- tary systems, includ- ing our own.” Exoplanet research has gone beyond the point of finding planets — more than 3000 exoplan- ets are now known — to looking for chemical markers that might indicate the potential pres- ence of life. A vital step is determining which molecules could indicate life, but establishing re- liable markers re- mains a tricky pro- cess. “ALMA’s dis- covery of organohalogens in the interstellar medium also tells us something about the starting condi- tions for organic chemistry on plan- ets. Such chemistry is an important step toward the origins of life,” adds Karin Öberg, a co-author on the study. “Based on our discovery, or- ganohalogens are likely to be a con- stituent of the so-called ‘primordial soup’, both on the young Earth and on nascent rocky exoplanets.” This suggests that astronomers may have had things around the wrong way; rather than indicating the pres- ence of existing life, organohalo- gens may be an important ele- ment in the lit- tle-understood chemistry in- volved in the ori- gin of life. Co-author Jes Jørgensen from the Niels Bohr In- stitute at Univer- sity of Copenha- gen adds: “This result shows the power of ALMA to detect mo- lecules of astro- biological interest to- ward young stars on scales where planets may be forming. Using ALMA we have previously found pre- cursors to sugars and amino acids around different stars. The additional discov- ery of Freon-40 around Comet 67P/C-G strengthens the links between the pre-biological chem- istry of distant protostars and our own Solar System.” The astronomers also compared the relative amounts of Freon-40 that contain different isotopes of chlo- rine in the infant star system and the comet — and found similar abun- dances. This supports the idea that a young planetary system can inherit the chemical composition of its parent star-forming cloud and opens up the possibility that organohalogens could arrive on planets in young systems during planet formation or via comet impacts. “Our results shows that we still have more to learn about the formation of or- ganohalogens,” concludes Fayolle. “Additional searches for organo- halogens around other protostars and comets need to be undertaken to help find the answer.” A pproximate loca- tion of Comet 67P/Churyumov– Gerasimenko when the ROSINA instru- ment on ESA’s Rosetta space probe discov- ered traces of Freon- 40 (methyl chloride), the same molecule de- tected by ALMA around the IRAS 16293-2422 star-form- ing region. [B. Saxton (NRAO/AUI/NSF)] T his video summarizes the discovery of Freon-40 around both IRAS 16293-2422 and comet 67P/C-G. [ESO] !