Salts: the secret catalyst of ice evolution on the path to biomolecules in planetary systems

Supervisors: Melissa McClure and Ewine van Dishoeck

https://local.strw.leidenuniv.nl/jobs/phd/example_phds.php

Deadline: November 15, 2025

Description: Life on Earth arose from a mixture of molecules with the elemental building blocks C, H, O, N, and S, which were delivered to our planet as solids, like ices and salts, during Earth's assembly. To understand the rise of life on Earth and the potential for life elsewhere, it is critical to trace the chemical evolution of ices from where they form in cold molecular clouds to where they are incorporated into planets within protoplanetary disks around young stars. Ammonium hydrosulfide salt was recently identified in interstellar ices based on JWST observations and laboratory experiments (https://www.astronomie.nl/nieuws/en/lost-sulfur-in-the-universe-found-in-salt-on-dust-and-pebbles-4349). Salt inclusions in interstellar ices may act as catalytic sites, as well as reactants in chemical pathways leading to the molecular building blocks of life. Additionally, they may provide reservoirs for key elements, especially N and S, during protostellar infall into the comet forming regions of protoplanetary disks.

In this project, the student will use our access to JWST and ALMA protostar programs to track the formation and chemical evolution of salts from clouds to disks. The student will be embedded within several international observing collaborations. Their work will take place within a joint Danish-Dutch astrochemistry consortium, InterCat (https://phys.au.dk/intercat), in conjunction with one other local PhD student and several students and postdocs at the Aarhus and Copenhagen nodes. Locally, they would be situated within the astrochemical planet formation group at Leiden, with several other PhD students and postdocs working on diverse topics.