"The Center for Interstellar Catalysis aims to discover the origin and evolution of the molecular building blocks of life - amino acids, nucleobases, sugars and fatty acids – in space"
As of 2025, close to 330 different molecules have been detected in interstellar space, with more added to the list each year. In our solar system the simplest amino acid, glycine, has been observed in comets, and meteorites routinely deliver a wide variety of the molecular building blocks of life to the surface of our planet. InterCat set out to determine the catalytic role of icy grain surfaces in the formation of the molecular building blocks of life in space and to address whether their synthesis predates the formation of new stars and planets. With access to the earliest James Webb Space Telescope (JWST) data, low temperature surface science techniques and new machine learning (ML) approaches, we have explored low temperature ice and dust structures, discovered non-diffusive, radical-driven formation pathways to amino acids and dust grain erosion reactions that lead to fatty acid formation.
"Could it be possible to form the molecualr building blocks of life in cold interstellar molecular clouds – even before the formation of stars and planetary systems?
If formed, would they be inherited through the different stages of star formation and end up in protoplanetary disks, and maybe even as parts of comets and meteorites?"
InterCat works towards our research goals by bringing together leading observational, computational and experimental groups within the fields of astrochemistry and surface science to determine whether the molecular building blocks of life can form in the low temperature solid phase, before the formation of new stars and planetary systems, and survive, and perhaps evolve in complexity, during the transition from clouds to protoplanetary disks. In conjunction, the InterCat team provide the necessary access to some of the strongest observational programs on JWST and ALMA; unique, custom built experimental setups – AU Chiralice, AU UVice, AU IR-STM and UL SURFRESIDE3 - aimed at studying low temperature astrochemical reactions and energetic processing under interstellar conditions; and cutting edge ab initio and machine learning-based calculations and models of interstellar ice and dust structures, and astrochemical reactions.
This combination allows for atomic and molecular level interpretations of experimental results via theoretical simulations, while ensuring that the systems studied adhere to the real constraints and characteristics of interstellar dust, molecular clouds and protoplanetary discs, as determined by JWST and ALMA observations.
InterCat Research takes place within the framework of three research themes. These themes shape our efforts to meet the InterCat research targets.
JWST observations of interstellar ices, e.g., under the IceAge and JOYS+ programs, reveal their highly complex nature both in terms of chemical composition (increasingly complex molecular species) and structure (morphology, dangling bonds, ice segregation, layering and mixing, charge build-up and salts). InterCat combines insight from observations, theory and experiments to investigate the properties of such chemically and structurally complex ices.
Complex ices see minority species that are relevant reactants, such as COMs (e.g., toluene and methanol), polycyclic aromatic hydrocarbons, carbon chain molecules and amino acids encapsulated in ice matrices composed of simpole dominant species such as H2O, CO or CO2. Ammonium hydrosulfide salt, for example, was recently identified by InterCat in interstellar ices based on a combination of JWST observations and laboratory experiments. InterCat aims to understand how these minority species can react via non-diffusive or “dark chemistry” pathways, while investigating energy dissipation, and ice restructuring and desorption. We can do this by exploiting the synergy between InterCat and IRASTRO, where we aim to develop the AU IR-STM to map the packing and IR spectral features of mixed molecular ices at the level of their individual molecular constituents. This will provide unique information about the influence of the local chemical environment on the IR spectral features of interstellar ice molecules, as well as insights into how they arrange on surfaces. We also take advantage of the LISA endstation at HFML-FELIX to measure IR spectra and IR-induced structural changes and desorption. We also emply machine learning- and molecular dynamics-based approaches to determine the IR spectra of both minority species and more abundant species that may experience spectral shifts in the mixed ices for comparison with observations.
While focus in astrochemistry has traditionally been on diffusion driven reactions, we now place emphasis on radical driven, non-diffusive chemistry. For example, an incoming radical, e.g., a hydrogen or oxygen atom, reacts with a molecule on the surface either by abstraction or addition, turning the molecule itself into a radical that may react with neighbouring molecules to form increasingly complex molecular structures. Such reactions are sometimes referred to as “dark chemistry” and have been shown to drive the formation of glycine.
Within InterCat, we study radical driven “dark chemistry” reactions that can lead to amino acid formation beyond glycine, the formation of sugars, carbon-chemistry pathways to fatty acids and nucleobase formation. In some cases these reactions may occur via catalytic and erosion reactions with interstellar dust-grain-analogues. We study these reactions in the laboratory using surface science techniques and have developed machine learning techniques to model reaction parameters in silico.
The greatly enhanced sensitivities of ALMA and JWST have brought forward new possibilities for characterizing the isotopic compositions of molecules in the gas- and solid-phases. The D/H abundance ratios of molecules are seen to be significantly enhanced during the cold phases. At InterCat, we investigate how such isotope ratios can be used as tracers of molecular formation environments and subsequent evolution, using data from ALMA and JWST programs in combination with experimental data and computer simulations to provide an overview of the isotope fractionation evolution in the gas and ices from cold molecular clouds to emerging protoplanetary disks.
The formation and evolution of molecular complexity in ices is impacted by energetic processing related to cosmic rays and radiation associated with the transition from dense molecular clouds to protoplanetary disks surrounding young stars. Specifically, regarding the evolution of the molecular building blocks of life under energetic processing, such processing may on the one hand result in destruction of the molecular building blocks of life and on the other hand result in the formation of even more complex molecular species, e.g., peptide chains as demonstrated by InterCat experiments. Also, energetic processing with circularly polarized light of molecular ices containing chiral molecules such as amino acids and sugars may induce enantiomeric excess and provide a possible interstellar pathway to the chiral selectivity that governs amino acids and sugars in terrestrial life today.
At InterCat we use the AU UVice and the AU IRice setups to record vacuum ultraviolet (VUV; 0.1-0.3 μm), ultraviolet-visible (UV-VIS; 0.3-0.8 μm), and IR absorption spectra of complex ices before and after exposure to VUV/UV radiation and/or energetic particles (10 keV protons or 5 keV electrons). The obtained spectra facilitate future observation of COMs in complex, energetically processed ices and produce VUV/UV photoabsorption cross sections of COMs with information on electronic excitation and ionization energies.
