Séminaire IPAG

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Unveiling the dark side of pre-stellar ice chemistry with the JWST Ice Age ERS program

jeudi 2 février 2023 - 11h00

Melissa McClure - Leiden University
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Volatile elements, like C, H, O, N, and S, are critical to the detectability of planetary atmospheres and the origins of life as we know it. These elements are mostly carried by icy dust grains that may have been transferred to Earth from the cold outer regions of the Solar protoplanetary disk. A substantial fraction of this ice is thought to have originated in the Sun's natal molecular cloud; however, the total amount and variety of ices inherited this way is an open question. Additionally, the chemical complexity achieved by the ices is unclear; interstellar complex organic molecules (COMs, >6 atoms, including C) are seen in the gas phase of dense clouds and in cometary ices, but whether they form as ices or not is hotly debated. These questions are critical to understanding planetary habitability and the rise of life, and they could allow us to use the atmospheric composition of giant planets to trace their formation zones in protoplanetary disks. Infrared spectroscopy of clouds, protostars, and protoplanetary disks with JWST allows us to answer these questions. In this talk I will present the first results from the JWST Early Release Science program Ice Age (http://jwst-iceage.org/), for which I am the PI, which are published in a recent article (link below). These results showcase the exquisite data quality from JWST and reveal the diversity of icy chemistry found in dark regions of molecular clouds. We present a new budget for the C, O, N, and S budgets of ices in the cloud and our understanding of the chemical pathways by which ices form, including evidence for early formation of methanol, the simplest COM, in water rich ice mixtures and a potential detection of ethanol in this cloud. I will end with a discussion of the implications of these results for planetary compositions and the progress of the next stages of the Ice Age ERS program. Our paper, McClure et al. (2023), is published in Nature Astronomy and freely downloadable here https://rdcu.be/c31ur). These results have been featured in a NASA press release, with ESA/NASA graphics (https://www.nasa.gov/feature/goddard/2023/webb-unveils-dark-side-of-pre-stellar-ice-chemistry).

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Hôtes : Romane Le Gal

Salle Manuel Forestini, 414 rue de la piscine, 38400 Saint Martin d'Hères