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The first solids formed in the Solar System record an unusual oxygen isotope signature that is distinct from that of Earth. Their 17O/16O and 18O/16O variations follow a nearly one-to-one relationship, rather than the relationship expected from conventional mass-dependent isotope fractionation. This mass-independent signature provides an important constraint on the physical and chemical environment of the early Solar System. CO photolysis and associated isotopic self-shielding processes, well known from astronomical studies of molecular clouds and protoplanetary disks, have been widely proposed as mechanisms for generating this signature. In this talk, I will reassess the fundamental assumptions behind this model and show theoretically that isotope-selective CO photodissociation may not produce the observed isotope relationship. These results motivate a broader search for alternative chemical pathways within the protoplanetary disk that could account for the oxygen isotope anomalies of the earliest Solar System solids. Understanding these processes may bring us closer to the chemical starting point of the Solar System.

BIO

Mang Lin holds a PhD in Chemistry from the University of California San Diego and is currently a professor at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. His research focuses on the fundamental physical chemistry of isotope effects and their applications to atmospheric, Earth, and planetary sciences, with particular interests in the origins and evolution of the Solar System, Earth, and life. His work has been published in high-impact multidisciplinary journals, including 9 papers in PNAS and 2 in Science Advances, and has been recognized with several awards, including the Shen-Su Sun Medal, the China Youth Science and Technology Award, and the CIFAR Azrieli Global Scholar Award.

Host: Xuening Bai