PhD defence

Transformation and sublimation of interstellar ices: insights from laboratory experiments and astronomical observations

• J. de Carvalho Santos

Date

Wednesday 2 July 2025

Time

10:00 - 11:00 hour

Address

Academy Building
Rapenburg 73
2311 GJ Leiden

Supervisor(s)

• Prof.dr. E.F. van Dishoeck
• Prof.dr. H.V.J. Linnartz

Summary

Stars and planets are born from cold clouds of gas and dust drifting through space. On tiny dust grains within these clouds, atoms and molecules freeze into icy layers---interstellar ices---where chemistry thrives, producing the building blocks of future planets and potentially life.

In my research, I combined laboratory experiments and telescope observations to study how these ices form, evolve, and eventually sublimate. By recreating the extreme conditions of space in the lab, I investigated the physicochemical processes that shape interstellar ices. I focused especially on sulfur-bearing ices, whose chemistry remains poorly understood despite sulfur’s key role in the biology of all living organisms.

Key findings of my thesis include the discovery of several new chemical pathways that explain how organic molecules form in ices---for example, challenging 20-year-old assumptions about the main formation route to methanol, a crucial precursor to life’s molecular building blocks. I also found that H2S ice can remain solid much closer to young stars than previously thought, making it available for incorporation into the cores of comets and icy planetesimals. Observations of gas-phase molecules around forming stars further helped trace the origins and fate of these ices.

Overall, these results shed new light on how the chemical makeup of interstellar space came to be, and which molecules can survive the journey from interstellar clouds to forming planets.

PhD dissertations

Approximately one week after the defence, PhD dissertations by Leiden PhD students are available digitally through the Leiden Repository, that offers free access to these PhD dissertations. Please note that in some cases a dissertation may be under embargo temporarily and access to its full-text version will only be granted later.

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