Free Astronomy Magazine May-June 2024

49 MAY-JUNE 2024 ASTRO PUBLISHING these and other molecules detected there by Webb represent key ingredients for making potentially habitable worlds. An international team of astronomers used Webb’s MIRI (Mid-Infrared Instru- ment) to identify a variety of icy compounds made up of complex organic molecules like ethanol (al- cohol) and likely acetic acid (an ingredient in vinegar). This work builds on previous Webb detec- tions of diverse ices in a cold, dark molecular cloud. “This finding con- tributes to one of the long-standing questions in astrochemistry,” said team leader Will Rocha of Leiden University in the Netherlands. “What is the origin of complex organic molecules, or COMs, in space? Are they made in the gas phase or in ices? The detection of COMs in ices suggests that solid- phase chemical reactions on the sur- faces of cold dust grains can build complex kinds of molecules.” As several COMs, including those detected in the solid phase in this research, were previously detected in the warm gas phase, it is now be- lieved that they originate from the sublimation of ices. Sublimation is to change directly from a solid to a gas without becoming a liquid. Therefore, detecting COMs in ices makes astronomers hopeful about improved understanding of the ori- gins of other, even larger molecules in space. Scientists are also keen to explore to what extent these COMs are trans- ported to planets at much later stages of protostellar evolution. COMs in cold ices are thought to be N ASA’s James Webb Space Telescope’s MIRI (Mid-Infrared Instrument) has identified a wealth of complex, carbon-containing (organic) molecules surrounding two protostars. This graphic shows the spectrum of one of the two protostars, IRAS 2A. It includes the fin- gerprints of acetaldehyde, ethanol, methylformate, and likely acetic acid, in the solid phase. These and other molecules detected there by Webb represent key ingredients for making potentially habitable worlds. [NASA, ESA, CSA, Leah Hustak (STScI)] easier to transport from molecular clouds to planet-forming disks than warm, gaseous molecules. These icy COMs can therefore be incorpo- rated into comets and asteroids, which in turn may collide with form- ing planets, delivering the ingredi- ents for life to possibly flourish. The science team also detected sim- pler molecules, including formic acid (which causes the burning sen- sation of an ant sting), methane, formaldehyde, and sulfur dioxide. Research suggests that sulfur-con- taining compounds like sulfur diox- ide played an important role in driving metabolic reactions on the primitive Earth. Of particular interest is that one of the sources investigated, IRAS 2A, is characterized as a low-mass proto- star. IRAS 2A may therefore be sim- ilar to the early stages of our own solar system. As such, the chemicals identified around this protostar may have been present in the first stages of development of our solar system and later delivered to the primitive Earth. “All of these molecules can become part of comets and asteroids and eventually new planetary systems when the icy material is transported inward to the planet-forming disk as the protostellar system evolves,” said Ewine van Dishoeck of Leiden University, one of the coordinators of the science program. “We look forward to following this astro- chemical trail step-by-step with more Webb data in the coming years from ORCs.” !