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Department of Astronomy 2022-2023 Colloquium Series Presents:

Melissa McClure, Assistant Professor, Leiden University
Thursday, March 23, 2023
3:30-4:30 PM
411 West Hall Map
"A new Ice Age: Tracing frozen volatile chemistry from clouds to comets with JWST."

Abstract: 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 some first results from several JWST programs of which I am the PI, including the ERS program Ice Age (, showcasing the exquisite data quality from JWST. These observations reveal the diversity of icy chemistry found in dark regions of molecular clouds and the distribution of ice and gas in protostars and disks. The ice profiles seen at high resolution allow us to probe the icy grains' size and chemical pathways by which ices form. I will end with a discussion of the implications of these results for comparisons with ALMA and exoplanetary compositions.

Our Ice Age paper, McClure et al. (2023), is published in Nature Astronomy and freely downloadable here These results have been featured in a NASA press release, with nice graphics (
Building: West Hall
Event Type: Lecture / Discussion
Tags: Physics
Source: Happening @ Michigan from Department of Astronomy, Michigan Institute for Research in Astrophysics