A New Laboratory Experiment to Explore the Icy Origins of Comet and Meteoritic Organics

Marissa Ann Maney, Karin I Oberg, Mahesh Rajappan

Meteorites and comets both contain rich organic reservoirs. These organic reservoirs may have influenced the initial organic chemistry on Earth and other planets, and also offer unique constraints on the importance of interstellar chemistry for prebiotic organics during planet formation. However, it is unclear what fraction of the organic material originates from cold, interstellar, protostellar, and disk ice chemistry versus aqueous or igneous chemistry in the parent body. To address this unknown, we have built a new instrument, designed to expose interstellar ice analogs to large doses of UV irradiation, and to readily extract the resulting complex organic residue. The latter is then externally analyzed using mass spectrometry. The instrument consists of a dual vacuum chamber, dual translation arm, sample storage unit, and glove box which are used in tandem to transport and package samples while managing the large pressure (5E-10-760 torr) and temperature (10-300 K) differentials that the samples are exposed to. In an experiment, the ices are irradiated for ~1-3 days, heated to room temperature, removed from the chambers, and packaged under an inert atmosphere for ex-situ analyses. Once fully operational, we expect to produce ~100 irradiated ice samples annually. We will use isotopically labeled ices to track the propagation of key reactants and constrain common pathways of specific organics, such as amino acids.
In this work, we introduce the new set-up, present our commissioning experiments, and discuss how our first results may elucidate the connection between ice photochemistry and the origins of specific meteoritic and cometary organic molecules.