Life detection in space exploration is strongly influenced by our understanding of life on Earth. However, focusing solely on "life as we know it" risks overlooking traces of unknown life. Instead of searching for specific molecules associated with terrestrial life, we propose prioritizing the detection of universal functional traits of life.

Assembly Theory (AT)¹ is an agnostic biosignature framework proposing that life produces complex objects in abundance. AT determines the complexity of an object by calculating the smallest number of unique steps required to construct it, based on graph theory. Additionally, the copy number of an object—specific to the investigated environment—is factored in, reflecting how living systems select to produce objects that enhance information storage, stability, or survival. While the theoretical foundation of AT for life detection is well established, particularly for organic molecules, further work is required to use AT for sample interpretation in space exploration. Previous studies have demonstrated AT calculations using data from spectroscopy techniques (IR and NMR)² and mass spectrometry (direct infusion ESI-MS and LC-MS)^1,3. However, LC-MS is currently unsuitable for space missions due to challenges such as solvent weight and the difficulty of mixing solvent gradients in microgravity.

Gas chromatography-mass spectrometry (GC-MS) offers a well-established instrument alternative for space exploration³, addressing the limitations of LC-MS while still providing analyte separation. GC-MS was deployed in the Viking mission in 1976, is currently used by Curiosity's SAM instrument, and will be featured in future missions like MOMA on the Rosalind Franklin Rover and DraMS on Dragonfly. Given its heritage and future applications, an experimentally validated GC-MS agnostic biosignature method is urgently needed.

Adapting AT estimations for GC-MS requires careful consideration of several parameters, including column selection, derivatization methods and consideration towards sample matrices. We will present preliminary test results of AT estimations using GC-MS and discuss how operational choices may impact the performance of this biosignature detection method. Developing a robust agnostic biosignature method compatible with instruments already deployed provides new opportunities for advancing life detection and interpreting space mission data.

1. Marshall, S.M., Mathis, C., Carrick, E. et al.Identifying molecules as biosignatures with assembly theory and mass spectrometry. Nat Commun 12, 3033 (2021). DOI: 10.1038/s41467-021-23258-x

2. Jirasek, M., Sharma, A., Bame, J. R. et al.Investigating and Quantifying Molecular Complexity Using Assembly Theory and Spectroscopy. ACS Central Science (2024). DOI: 10.1021/acscentsci.4c00120

3. Weiss, G.M., Asche, S., Graham, H.V. et al. Operational considerations for approximating molecular assembly by Fourier transform mass spectrometry. Astron. Space Sci., 11 (2024). DOI: 10.3389/fspas.2024.1485483

4. Luoth, C., Mahaffy, P., Trainer, M. al. Planetary Mass Spectrometry for Agnostic Life Detection in the Solar System. Front. Astron. Space Sci., 8 (2021). DOI: 10.3389/fspas.2021.755100

How to cite: Asche, S., Weiss, G. M., and Graham, H. V.: Experimental assembly theory estimations with gas chromatography-mass spectrometry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13309, https://doi.org/10.5194/egusphere-egu25-13309, 2025.

Terrestrial (carbon-based) biochemistry relies on chemical functionality introduced by heteroatoms. Among them, the nitrogen atom (N) defines the (bio)chemical properties of crucial building blocks of life such as amino acids (AAs) and nucleobases (NBs). However, it has not been clear until today whether these building blocks of life on Earth were synthesized from simple prebiotic molecules on the young planet itself or rather delivered by impacting material. Comets not only carry some of the most pristine and original material in our Solar System, but also may have delivered substantial amounts of organics to the early Earth through impacts (Marti et al. 2017, Rubin et al. 2019). From studying comets, we can thus learn about the prevalence of such complex organic molecules (COMs) in space.

An unprecedented milestone in cometary science was the European Space Agency’s Rosetta mission that rendezvoused with comet 67P/Churyumov-Gerasimenko mid-2014. Rosetta studied this comet up close for two years, sending a huge amount of invaluable data back to Earth. One of the key instruments to study the chemical composition of the cometary outgassing was the high-resolution Double Focusing Mass Spectrometer (DFMS) – part of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA; Balsiger et al. 2007). It unveiled a surprising organic diversity and complexity. In the past, we applied an Occam’s razor-based spectra deconvolution approach to identify as many cometary COMs as possible and we found strong evidence for the presence of O- and N-bearing heterocycles (Hänni et al. 2022, 2023, in prep.). However, the ambiguity introduced by structural isomerism often hampers the assignment of a detected signal (chemical sum formula) to a specific molecular structure as different isomers usually have very similar mass-spectrometric fingerprints. Moreover, under the assumption of a bottom-up chemistry, Occam’s razor may not be capable of capturing the emergent chemical diversity. Here, we want to highlight another perspective on the cometary data: If a specific molecule yields a strong molecular ion signal (i.e., a signal of the unfragmented parent molecule) according to its reference mass spectrum, and if this molecular ion signal is not detected, then this molecule’s presence can be ruled out, even if the analyte is as complex as a cometary coma. We therefore investigate the detectability (by electron-ionization mass spectrometry) and the presence/absence of the N-bearing building blocks of life, which are the biogenic nucleobases and amino acids. First, preliminary results suggest that the presence of bionic nucleobases can be ruled out within error margins. However, for amino acids, which do not normally yield strong molecular ion signals, the case is less clear cut. We argue that a typical amine fragment is limiting and can be used to constrain the total abundance of amines. We will compare our findings with asteroidal carbonaceous matter.

Marti et al. Science (2017) 356, 6342, 1069-1072.

Rubin et al. ACS Earth Space Chem. (2019) 3, 1792−1811.

Balsiger et al. Space Sci. Rev. (2007) 128, 745-801.

Hänni et al. Nat. Commun. (2022) 13, 3639.

Hänni et al. Astron. Astroph. (2023) 678, A22.

Hänni et al. in prep. for Astron. Astroph.

How to cite: Hänni, N., Altwegg, K., Baklouti, D., Bonny, R. F., Combi, M., Doriot, A., Fuselier, S. A., De Keyser, J., Müller, D. R., Rubin, M., and Wampfler, S. F.: About nucleobases and amino acids on comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7101, https://doi.org/10.5194/egusphere-egu25-7101, 2025.

Agent-based simulations are employed to describe the early biological selection of oligomers made of monomers with different chirality. These simulations consider the spatial distribution of agents and resources, the balance of biomass of different chirality and the balance of chemical energy. In line with prebiotic chemical models, a disadvantage is attributed to the change in chirality within the biochemical sequence. The model includes a racemic amino acid pool, based on evidence from meteorites and Miller’s experiments. It is also assumed that the earliest life forms, being extremely primitive, were heterotrophic. Under these assumptions, the simulations show that biological sequences are not strictly homochiral but exhibit a few chirality changes. These results suggest that the current dominance of homochiral species may have been preceded by a more structurally varied biochemistry. This could be reflected in the few existing heterochiral proteins, which do not conform to the typical structures of alpha-helices or beta sheets. Alternative biochemistries might rely on such heterochiral proteins.

How to cite: Longo, S., Micca Longo, G., and Casimo, G.: Were heterochiral polymers relevant in primordial and extraterrestrial life scenarios?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3111, https://doi.org/10.5194/egusphere-egu25-3111, 2025.

Formaldehyde (CH₂O) is known as an important building block in the formation of prebiotic molecules including sugars and amino acids. It is therefore regarded as a crucial precursor for the origin of life on early Earth. For this, however, it must have either been delivered via comets and meteorites or formed directly in Earth’s early atmosphere via photochemical synthesis such as the photoreduction of CO₂ with H₂O (e.g., Cleaves 2008). In their seminal paper, Pinto et al. (1980) were the first to simulate the photochemical production of formaldehyde in Earth’s primitive atmosphere, which they assumed to mostly contain N₂ with minor abundances of CO₂, H₂O, H₂, and CO. Their chemical network resulted in substantial photochemical production of CH₂O of up to 10¹¹ mol/year, indicating that photochemically produced formaldehyde could have indeed been an important building block for prebiotic chemistry on early Earth. By assuming the same boundary conditions (i.e., atmospheric composition, solar flux, eddy diffusion coefficient, etc.), we can reproduce the results by Pinto et al. (1980) with the photochemical atmosphere model ARGO and its chemical network STAND (e.g., Rimmer et al. 2021). By simulating early Earth’s atmosphere with a more realistic composition based on recent geophysical and aeronomical results, and by implementing the flux of the early Sun, we even obtain slightly higher formaldehyde production rates as found by Pinto et al. (1980), thereby further supporting photochemistry as an important source for formaldehyde at the time of life’s origin. In addition, we also investigate the rainout of formaldehyde in Earth’s early atmosphere, a process that could have led to the concentration of CH₂O in pools of early volcanic islands – a potential location for the origin of life.

Acknowledgement: thank the Austrian Science Fund (FWF) for the support of the VeReDo research project, grant I6857-N .

References:

Cleaves II HJ, 2008, The Prebiotic Geochemisty of Formaldehyde, Precambrian research, 164, 111-118.

Pinto JP, Gladstone GR, Yung YL, 1980, Photochemical Prduction of Formaldehyde in Earth’s primitive Atmosphere, Science 210, 4466, 183-185.

Rimmer P, Jordan S, Constantinou T, Woitke P, Shorttle O, hobbs R, Paschodimas A, 2021, Hydroxide Salts in the Clouds of Venus: Their Effect on the Sulfur Cycle and Cloud Droplet pH, PSJ, 2, 4, id133.

How to cite: Scherf, M., Constantinou, T., Rimmer, P., Woitke, P., Lammer, H., Ferus, M., Eminger, P., Němečková, K., Kačina, J., and Cassone, G.: Photochemical Production of Formaldehyde on Early Earth Revisited, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11745, https://doi.org/10.5194/egusphere-egu25-11745, 2025.

In this study we compare the infrared and Raman micro-spectroscopy signatures of the Asuka 12236 and Paris meteorite, both considered among the most primitive in the carbonaceous chondrites collection.

The obtained average spectrum from the mid to far infrared of Asuka 12236 reveals the presence of anhydrous minerals as well as a possible contribution of amorphous silicates. Aromatic primary amines and imines heterogeneously distributed within Asuka 12236 are also reported. These components are not found in the average spectrum of Paris.

The richness of Asuka 12236 in nitrogen bearing components, could give clues to its parent’s body. It could originate from regions at large heliocentric distances where the bodies are known to be nitrogen-rich.

In addition, the D and G Raman bands of the two meteorites clearly show that the aromatic carbons of Asuka 12236 are less structured than those of Paris, suggesting thus different thermal histories for the two meteorites.

All our results confirm that Asuka 12236 is an exceptional meteorite, more primitive than Paris. The two CM chondrites should be compared to the pristine extraterrestrial materials returned to Earth by the space missions such as Ryugu (Hayabusa 2) and Bennu (OSIRIS-Rex) even if they are CI’s like.

How to cite: Djouadi, Z., Vinogradoff, V., Dionnet, Z., Serra, C., Dimitrijevic, D., Malnuit, A., Lantz, C., Claeys, P., Goderis, S., and Le Sergeant d'Hendecourt, L.: Comparison of micro-spectroscopic signatures of 2 peculiar CM-type meteorites: Asuka 12236 and Paris., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2732, https://doi.org/10.5194/egusphere-egu25-2732, 2025.

In typical astrophysical environments, where temperatures and densities are very low and radiation fluxes may be high, the transformation of simple molecules in the gas phase is difficult. Consequently, it is widely accepted that the formation of interstellar complex organic molecules (iCOMs) occurs through barrierless reactions or on the surface of dust grains, which are present in all stages of the evolution of a planetary system. Those grains can act as third bodies, absorbing excess energy from reactions, and are also covered in ices (mainly made of water, CO, N2 and other simple organics, such as methanol) which act to concentrate reactants, increase the chances of reactive collisions, and/or protect from radiation newly formed molecules.

However, models generally assume that reactions occur on the ice phase covering the silicate cores, and tend to minimise the chemical role played by
the dust grains themselves. When grains are not covered in ice, interactions between the solid phase and the gas phase are also important. Indeed, dust grains can be a source of reactants and are also rich in metallic components, such as Fe and Ni. These metals are well known on Earth to act as catalysts for the synthesis of organic compounds, such as the Fischer-Tropsch synthesis (FT) to produce hydrocarbons, the Haber-Bosch (HB) for the synthesis of ammonia, and the cyclation of small hydrocarbons in Diels-Alder (DA) type reactions and further formation of aromatics and nanostructures. They also contain FeS phases, such as troilite or pyrrothite, which are also known to be reactive and could be important to the incorporation of S in complex iCOMs.

Different works have already pointed to the importance of bare grain chemistry (Cazaux et al., 2010; Frankland et al., 2016), and in particular, of the catalytic activity of metallic inclusions (Llorca and Casanova, 2000; Ferrante et al., 2000; Tucker et al., 2018; Peters et al., 2023) and their potential role
in the chemical evolution of different astrophysical environments. In this talk, I will discuss the results of our last experiments which are part of our Astrocatalysis project, which aims at investigating relevant catalytic processes that could occur in different astrophysical environments, such as primeval planetary surfaces and atmospheres. I will present our experiments on the reactivity of chondritic material under relevant protoplanetary conditions toward FT synthesis (Cabedo et al., 2021) and towards the formation of H2S (Cabedo et al., 2024). I will also present future experiments regarding the reactivity of the material after ablation with plasma (Cabedo et. al., 2025, in prep.), simulating the potential reactivity of entering material during early stages after planetary formation. Understanding dust grains solid chemistry is important to completely interpret observational data and to have a complete model of the evolution of iCOMS at different stages of star and planetary formation and towards complex organic chemistry.

How to cite: Cabedo Soto, V., Allitt, J., Pareras, G., Rimola, A., Yiu, H., and McCoustra, M.: Reactivity of meteoritic material in different astrophysical environments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10316, https://doi.org/10.5194/egusphere-egu25-10316, 2025.

Comets and asteroids are among the most pristine objects in the Solar System, being formed out of the materials available in the proto-Solar Nebula [3]. Especially interesting are the complex organic molecules in these bodies, as they likely contribute towards the elemental composition of forming planets, as well as potentially being delivered after accretion of planetary bodies via impacts and thus contribute to their molecular inventory [4, 5].

Many primitive solar system objects, such as carbonaceous chondrites or interplanetary dust particles (IDPs), contain organic matter, which itself can be divided into a solvent-soluble (soluble organic matter, SOM) and insoluble fraction (Insoluble Organic Matter, IOM) [1, 6]. The formation environment of the IOM, which mainly consist out of macromolecules, is an area of ongoing research and IOM could have formed either in the interstellar medium or in the proto-Solar Nebula [5].

Even though it makes up the majority of the organic carbon in solar system objects, IOM has not been extensively studied in the laboratory. However, the formation pathways of IOM are crucial to understand the complex – insoluble – organic molecules available for the formation of planetary bodies. In this study, irradiation experiments on ice are performed with the ICEBEAR setup [2]. The setup consists of a stainless-steel vacuum chamber with base pressures of mbar. Vacuum-grade aluminium foil is fixed onto a copper sample holder, which is mounted on the cold head of a closed cycle helium cryostat, allowing for cooling of the sample holder to ~5 K.

A H₂O:CH₃OH:N₂ gas mixture is leaked into the chamber, where it adsorbs onto the cold (~10 K) aluminium foil, forming an ice film on the aluminum foil. Next, the ice is irradiated with 5 keV electrons, resulting in the formation of soluble organic matter. For several samples, a second irradiation is performed, which has been observed to lead to the formation of a darker residue, presumed to be insoluble organic matter.

The produced residues are analysed using micro-Raman spectroscopy at ETH Zürich with a laser operating at 532 nm. Raman spectroscopy is a powerful tool to investigate the structure of carbonaceous material. Especially interesting are the D (disordered) and G (graphite) bands of carbon. The peak widths and positions of the two bands, as well as their ratio, give valuable information about the structural order of the material. The results are compared to IDPs, which are thought to contain some of the most primitive organic matter in the solar system [6].

The initial analysis of the residue of a double irradiated ice sample with micro-Raman spectroscopy hints towards the formation of amorphous carbon that resembles the IOM extracted from IDPs.

[1] Garcia et al., ACS Earth and Space Chemistry, 2024. doi: 10.1021/acsearthspacechem.3c00366

[2] Kipfer et al., Icarus, 2024, doi: 10.1016/j.icarus.2023.115742

[3] Caselli & Ceccarelli, Astron Astrophys Rev 20, 2012, doi : 10.1007/s00159-012-0056-x

[4] Chyba & Sagan , Nature, 1992, doi: 10.1038/355125a0

[5] Alexander et al. Geochemistry, 2017, doi: 10.1016/j.chemer.2017.01.007

[6] Riebe et al., Earth and Planetary Science Letters, 2020, doi: 10.1016/j.epsl.2020.116266

How to cite: Kipfer, K. A., Ligterink, N. F. W., Allen, N. M., and Riebe, M. E. I.: The origin of Insoluble Organic Matter: Formation of macromolecules from heavily irradiated simple ices, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21930, https://doi.org/10.5194/egusphere-egu25-21930, 2025.