TP15

To be sustainable, a settlement on Mars should be as independent of Earth as possible in terms of material resources. This independence may be reached with the help of biological systems: those could perform a wide range of functions with a low impact on the surroundings. However, biological systems would best rely on resources available on Mars – as recycling alone would mean that the amounts of available resources decrease over time – and most organisms cannot utilize raw Martian resources directly.

A solution has been proposed which lies in using diazotrophic, rock-weathering cyanobacteria. Their physiology is such that they could, it seems, be fed with materials available on site: water mined from the ground or atmosphere; carbon and nitrogen sourced from the atmosphere; and the local regolith, from which it has been argued that they could extract the other necessary nutrients. The cultured cyanobacteria could then produce various consumables directly, such as dioxygen and dietary supplements but also support the growth of secondary producers (plants or microorganisms) which could, in turn, generate a wide range of critical consumables.

Various proofs-of-concept have been reported in the literature and evidence accumulates that some cyanobacteria could, indeed, be fed from Martian resources and provide feedstock for other organisms of biotechnological interest. But whether a system works at all is not sufficient to decide whether it should be integrated into mission plans: its cost-efficiency must be determined and compared to potential alternatives.

Among the factors that will determine this cost-efficiency is the fitness of cyanobacteria under (i) hypobaria (low pressures), and as a result low partial pressures of dinitrogen; and (ii) a dependence on regolith for all nutrients not provided as gases, which would also lead to high concentrations of highly oxidizing compounds (chiefly, perchlorates) in the extracellular medium. Another key element is the design of specific cultivation hardware.

In this presentation, we will present the wet-lab and in-silico work performed at the ZARM’s Laboratory of Applied Space Microbiology to study those factors and thereby assess, and improve, the efficiency of cyanobacterium-based, biological ISRU on Mars.

How to cite: Verseux, C. and Ramalho, T.: On the cost-efficiency of cyanobacterium-based, biological ISRU on Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-57, https://doi.org/10.5194/epsc2022-57, 2022.

1. Introduction

Río Tinto (Huelva, Spain) is one of the largest natural acid environments in the world and a mineralogical analog of Mars. The peculiarities presented by the system are due to the high concentration of ferric ion (Fe⁺³) contained in its waters, which is responsible not only for its characteristic red color, but also for maintaining a constant acidic pH (≈2.3) along the almost 100km length of the river [1]. Results obtained in the MARTE and IPBSL drilling projects suggested that the origin of the high concentration of Fe⁺³ is due to the metabolic activity of a subsurface "bioreactor" which is capable of dissolving pyrite, the main metal sulfide in the Iberian Pyrite Belt (IPB) [2].

In order to verify this hypothesis, we have developed a numerical model to analyze the hydrodynamic behavior of the groundwater inside one of the geologic faults of the system as well as the generation and transport of the Fe⁺³ in solution. As input parameters for the model, we have used the hydrogeological (topography, mineralogy, water table...), physicochemical (iron concentration, oxygen presence, porosity...) and microbiological (pyrite dissolution rate mediated by microorganisms) data obtained after years of study of the ecosystem of Río Tinto [2].

2. Methods

2.1. Biological model

To calculate the iron release mediated by microorganisms along the fault (marked in red in Figure 1A), three different scenarios were considered depending on their pyrite content and oxygen concentration: case 1) oxidizing layer; case 2) anaerobic zone of disseminated pyrite; and case 3) anaerobic zone of massive pyrite (see Figure 1B).

Figure 1: A) Satellite image of the Peña de Hierro area. The locations of the main faults (black solid lines), as well as those of the different acidic springs (yellow dots), are shown (image modified from [3]). B) Section of the fault studied. In blue, case 1. In grey, case 2. In red, case 3.

The contribution of iron to groundwater due to the biological action of subsurface microorganisms was measured by incubating natural surface and subsurface samples, the latter obtained during the IPBSL project, with water and monitoring iron release over time. Negative sterile controls were carried out in parallel.

2.2. Hydromechanical model

The numerical model used to simulate the generation and transport of Fe⁺³ in the groundwater of Río Tinto consists of two phases:

• Modeling the flow movement inside the porous medium by solving the seepage equations [4].
• Once the water velocity has been determined, the generation and transport of Fe⁺³ is modeled by solving the advection-diffusion equations with a source term.

3. Results

The equations considered for the hydromechanical model are solved numerically by using the Finite Element Method. To this end, a non-structured 2D mesh of 15473 linear triangular elements is used to model the sectional area of the selected geologic fault (marked in red in Figure 1A). After solving the seepage equations in the sectional area depicted in Figure 1B using the physical parameters shown in Table 1, the pressure field is determined and thus, the water velocity can be calculated.

Table 1: Input parameters for the model

Measurements from the incubation of natural rock samples with water in the different fault zones (Table 1) along with the water velocity calculated using the seepage model [4] are used as an input to model the generation and transport of Fe⁺³ in the subsurface of Río Tinto. The output of this model provides with the space distribution of the concentrations of Fe⁺³ in the sectional area of the fault, as shown in Figure 2A.

Figure 2: A) Space distribution of the concentrations of Fe³⁺ (kg_Fe/kg_H2O) calculated by the model. B) Evolution in time (s) of the concentration of Fe³⁺ (kg_Fe/kg_H2O) in the vicinity of spring 2 (red square in 2A)

The numerical results for the concentrations of Fe⁺³ as a function of time in the vicinity of the natural spring 2 (see Figure 1A) are shown in Figure 2B, being the average value 1.01e-3 kg_Fe/kg_H2O. It can be observed that the concentration of Fe⁺³ quickly stabilizes, keeping constant in time through the years. This is consistent with the experimental average values of 9.87e-4 kg_Fe/kg_H2O measured at spring 2, with suggests a relative error for the model-predicted value of about 1.94%.

4. Conclusion

Our results suggest that it is mathematically feasible that the Fe⁺³ measured in one of the natural springs of Río Tinto is a consequence of the activity of both aerobic and anaerobic microorganisms inhabiting the IPB subsurface, which supports the hypothesis of the biological origin of Río Tinto.

Acknowledgements 

This work is funded by the AEI (Spanish Research Agency), project MDM-2017-0737. We would like to gratefully acknowledge Universidad Carlos III de Madrid (Dto. Ingeniería Térmica y Fluidos) for the financial support.

References

[1] Amils, R., et al. (2008). Subsurface geomicrobiology of the Iberian Pyritic Belt. Microbiology of extreme soils. Springer, Berlin, Heidelberg: 205-223.

[2] Escudero Parada, C. (2018). Fluorescence microscopy for the in situ study of the Iberian Pyrite Belt subsurface geomicrobiology. Dissertation Thesis, UAM.

[3] Gómez-Ortiz, D., et al. (2014). Identification of the subsurface sulfide bodies responsible for acidity in Río Tinto source water, Spain. Earth and Planetary Science Letters 391: 36-41.

[4] Herreros, M.I., et al. (2006). Application of level-set approach to moving interfaces and free surface problems in flow through porous media. Computer Methods in Applied Mechanics and Engineering, 195 (1–3): 1-25.

How to cite: Herreros, I., Escudero, C., Gómez-Ortiz, D., Rodríguez, N., Martínez, A., Suárez-Gordo, A., Fernández-Remolar, D., Gómez, F., and Amils, R.: Modeling the origin of Río Tinto, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-118, https://doi.org/10.5194/epsc2022-118, 2022.

Introduction

The survivability of bacteria in planetary impacts has previously been investigated using a two-stage Light Gas Gun (as seen in Figure 1). During these experiments, projectiles were doped with bacteria (Rhodococcus erythropolis) and fired at hypervelocity into rock [1,2], metal [2], water-ice [3,4] and agar [4,5] targets. These experiments were designed to investigate the feasibility of the panspermia theory, which details how indigenous life forms may be spread beyond their host body via the ejecta created by hypervelocity impacts and go on to seed neighbouring bodies. These studies showed that bacteria do survive hypervelocity impact; however, the methods do not accurately quantify the survival rate on the target compared to the initial cell load on the projectile, nor do they quantify or characterise any sub-lethal effects.

Figure 1: The Light Gas Gun impact facility at the University of Kent.

Creating A Successful Target

Attempts have been made to develop new methods that give greater quantitative insights into both survival and sub-lethal effects of hypervelocity impacts. As well as investigating the survival rate of the bacterial population, we are looking at whether the transient extremes of pressure which occur as a result of hypervelocity impact modulate phenotypic change amongst the surviving bacteria, and thus could be a factor in the evolution of life.

The bacteria (in this case Escherichia coli) in our experiments have been placed inside the target instead of the projectile. This decision was made in order to remove the potential issues of the loss or death of cells as a result of the acceleration of the projectile. Several different target designs were trialled, largely involving the use of agar as a medium for housing the bacteria. These attempts led to a set of criteria being defined for a successful target, including efficient propagation of the shock wave through the sample to ensure that the bacteria are experiencing the intended conditions, and clean recovery of the majority of the sample with little or no contaminants.

The Liquid Target Setup

Following much experimentation, a liquid target setup was created, as seen in Figure 2. A 50 ml liquid sample containing the bacteria is housed inside a thin polythene bag and placed inside a steel tube, which upon impact collects the liquid and allows for ease of recovery and analysis. The impacted plastic bag produces a large amount of debris within the collected sample, which interferes with some of the optical data gathered during post-impact analysis of the bacteria. Also, there is concern that the entirety of the sample is not experiencing the full force of the impact. To address these issues, we are designing a secondary tube with a much smaller diameter which can be inserted and secured inside the primary steel tube; this should mean that more of the sample volume will experience higher shock pressures in the range of several GPa, which can be verified by simulating the impacts using Autodyn modelling. To replace the polythene bag, and thus attempt to minimise the quantity of debris entering the system, the liquid sample will be sealed directly inside the secondary tube with an extremely thin foil.

Impacts have been completed across the velocity range of 1-5 km/s using this setup. The following analysis methods have been applied to the recovered samples post-impact:

• OD₆₀₀ (optical density) recordings to understand changes in whole cell numbers by measuring the number of particles within a given sample
• Protein assays to understand the amount of physical damage or lysis to the cells
• Growth on agar plates to understand how the viability of the population has changed via the counting of colony forming units (CFUs)
• Oxygen electrode analysis to see if the metabolic pathways of the cells have been affected by measuring cellular respiration in the presence of glucose

So far, no significant changes to the survival rate or the phenotype of the population have been observed following these impacts using the analysis methods described.

Figure 2: The liquid target setup within the target chamber of the Light Gas Gun.

Influence of Exposure Time to Impact Conditions

The results from the liquid target impacts have raised the question of whether the extremely short duration of the shock pressure is insufficient to lead to any meaningful change in the bacterial population. To investigate this, E. coli samples prepared in the same manner as for the impacts are instead placed inside a sonicator, where the sound waves generate pressures within the sample of around 200 MPa, compared to the impact shock pressures of several GPa created in the Light Gas Gun. The sonication exposure times were varied, using 4 bursts of 0, 5, 10, 30 and 60 seconds, compared to the milliseconds or less that the peak shock pressures are applied to the sample in the Light Gas Gun.

A steady decline of surviving bacteria and a significant increase in cell lysis was observed as the exposure time was increased, supporting the idea that time is the key factor in generating populational changes. At burst exposure times of 30 seconds or more, an unusual phenotype emerges following growth of the sonicated samples in the form of a new colony type displaying a concentric ring pattern of growth, as shown in Figure 3. This is currently being investigated further with repeat experiments, antibiotic testing and 16S rRNA sequencing to confirm that this is indeed a change in phenotype and not a result of a separate factor such as contamination.

Figure 3: An agar plate spread with a sample of E. coli cells following 4 30-second bursts of sonication.

References

[1] Burchell et al. (2000) In Gilmour I., Koeberl C. (eds) Impacts and the Early Earth. Lecture Notes in Earth Sciences, vol 91.

[2] Burchell et al. (2001) Adv. Space. Res. 28(4), 707-712.

[3] Burchell et al. (2003) Origins of Life and Evolution of the Biosphere 33, 53-74 (2003).

[4] Burchell et al. (2004) Mon. Not. R. Astron. Soc. 352, 1273-1278 (2004).

[5] Burchell et al. (2001) Icarus 154, 545-547 (2001).

How to cite: Wilkinson, R., Wozniakiewicz, P., and Robinson, G.: Exploration of Methodologies to Investigate Bacterial Survival in Planetary Impacts, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-121, https://doi.org/10.5194/epsc2022-121, 2022.

Introduction:  A search for evidence of extant life on Mars provides a focusing goal for human exploration missions that are planned for the 2030s. Finding an example of extant life beyond Earth would be one of the greatest scientific discoveries of all time. Human exploration brings extraordinary improvements over robotic missions in both payload and analytical capability. Environments that may be habitable for modern life on Mars include salts and brines, ground ice, caves, and deep subsurface aquifers [Carrier et al. 2020]. The habitability case for each environment is reviewed as well as how human missions may enable the search. It is important to determine if life exists on Mars prior to human exploration activities to prevent both the risk to Earth of inadvertently bringing potentially harmful organisms from Mars, risks to astronaut health, and the complication of recognizing Mars life once terrestrial contamination has occurred.

Salts and Brines: Salts and evaporites are common at the surface of Mars [Osterloo et al. 2010] with at least 600 regions of chloride salts identified. On Earth, evaporites and associated brines support a wide diversity of microbial communities including phototrophs, lithotrophs, and heterotrophs [Das Sarma and Das Sarma 2017]. Endolithic phototrophs are found associated with gypsum crusts, and halite-entrapped halophilic archaea and bacteria are commonly observed in enclosed brine fluids, having easily detectable carotenoid pigments [DasSarma, et al. 2020]. Halite and gypsum minerals offer radiation protection by attenuating ultraviolet light and provide protection from long-term desiccation by deliquescence [Davila et al. 2010]. Dissolved salts extend the temperature range for maintaining liquid water through freezing point depression and by formation of supercooled liquids, expanding the possibility of life processes at subzero temperatures. Concentrated brines occur in ice vein networks where dissolved salts are excluded during ice formation. Because many salts are hygroscopic, liquid brines might form near the surface in locations that receive periodic frosts. The widespread presence of perchlorate salts on Mars allows brines to form over a large part of the Martian surface due to deliquescence [Rivera-Valentin et al. 2020]. The brines may form at temperatures too low for known terrestrial metabolism but more work is needed to understand their potential habitability. Salt environments are widely accessible to be studied by human missions with standard microbiological sampling methods.

Ice Rich Terrains: Shallow ground ice is widespread on Mars at latitudes above 35^o N /45^o S [Piqueux et al. 2019]. Quasiperiodic climate change results from variations in orbital parameters causing the intensity of incident sunlight at a given latitude to vary over time. As a consequence climate shifts occur and the location and depth of ground ice varies [Mellon and Sizemore, 2022]. Current summer surface temperatures in ice-rich midlatitude regions are sufficient to support life if melting surface ice or frost provides transient liquid water. Sampling ground ice to search for life can be accomplished with 1-2 m drilling systems operated by crews or rovers teleoperated by human crews. Flight prototype life detection instruments fed with a 1m auger drill have successfully identified biosignatures in Atacama Desert samples that were collected and analyzed during Mars mission simulations [Stoker et al. 2022].

Caves: Caves are another high priority environment in the search for extant life on Mars as they protect their interiors from cosmic radiation and energetic solar events, changing surface climatic conditions, and small-scale impact events. Caves can be warmer, wetter, and more protected, therefore more habitable than the surface. More than 1000 candidate caves in volcanic terrain have been identified on Mars from orbital imagery and many occur in the Tharsis volcanic complex area [Cushing et al. 2015]. A cave with natural openings offers direct access to the subsurface, with a relatively stable thermal environment that can persist over geologic time and preserve volatiles while voids with no surface openings are detectable via ground penetrating radar. Microbial life in terrestrial volcanic caves that lives on chemical energy derived from limited organic carbon and minerals is found on and in a wide variety of mineral features, from silica-rich, to carbonate, iron, and other metals distinctive from their basaltic host rock. Such features preserve microbes extremely well in situ. In some cases, obvious moist biofilms are found but in other cases mineral forms trap and preserve microbial structures that are revealed with microscopy (Boston et al. 2001). Cave morphology is complex and human capabilities are essential for exploring them, possibly aided by small helicopters to search for habitable conditions from the surface.

Deep Subsurface: Deep subsurface aquifers might be the longest-lived habitable environment on Mars, possibly existing from the Noachian until now (Onstott et al. 2019) . Physical access to the subsurface will require deep drilling systems, a technology that will likely require human presence to achieve success. Deep drilling would require a low-mass wireline approach as recently demonstrated drilling to 111m in Greenland ice.

References:

Boston, P.J. et al. 2001. Astrobiology 1(1), 25-55.

Carrier, B.L. et al. 2020. Astrobiology 20(6).

Cushing, G.E. et al. 2015. J. Geophys. Res. Planets 120, 1023-1043.

DasSarma, S. and DasSarma, P.  2017. Encyclopedia of Life Science, Wiley.

DasSarma, S. et al. 2020. Extremophiles 24, 31–41.

Davila, A.F. et al. 2010. Astrobiology 10, 617-628.

Mellon and Sizemore, 2021. Icarus 371, 114667.

Onstott, T.C. et al. 2019. Astrobiology 19(10), 1230–1262.

Osterloo, M.M. et al. 2010. J. Geophys. Res. 115:E10012.

Piqueux, S. et al. 2019. Geophys. Res. Lett. 46, 14290-14298.

Rivera-Valentin et al. 2020. Nature astronomy doi.org/10.1038/s41550-020-1080-9.

Stoker, C.R. et al. 2022. Astrobiology in review. ABSCICON 2022 Conference abstract.

Sun, H.J. 2013. Biology 2, 693-701.

How to cite: Stoker, C.: The Search for Extant Life on Mars as a Focusing Scientific Goal for Future Human Exploration Missions, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-181, https://doi.org/10.5194/epsc2022-181, 2022.

Exploring the limits of life is one of the objectives for better understanding how organisms have arisen on Earth, how they tolerate extreme conditions and how they might survive on other planets or moons. These investigations could help with understanding which Earth microorganisms could survive on other celestial bodies, such as the icy Moons: Europa (Jupiter) and Enceladus (Saturn). Furthermore, it might help with indicating how life could have developed on Earth or on the icy Moons of the Solar system. This project focuses on the insights from prokaryotic, eukaryotic and archaea organisms which can tolerate the simulated subsurface ocean environment of Europa and Enceladus. The moons have been speculated to have subsurface oceans which are heated by tidal movements or hydrothermal vents. These combined factors could create an environment suitable for life. Furthermore, the mechanism of radiation, desiccation and temperature survival could help us understand whether the organisms could survive a hitchhike on spacecraft surfaces travelling to the moons. During space exploration it is essential to avoid the contamination of planets and moons of astrobiological interest by microorganisms from Earth.

The projects’ main question is: What are the boundaries of tolerance for cold-adapted halophilic microorganisms as determined by simulated space conditions? Furthermore, we also want to investigate the survival to simulated icy moon conditions. At this stage of the project two organisms have been investigated, the bacterium Planococcus halocryophilus and the yeast Rhodotorula frigidalcoholis. Our aim is to use one organism from each domain of life: prokaryote, eukaryote and archaea. Preliminary results have shown a fair survival of R. frigidalcoholis but not of P. halocryophilus to some simulated space conditions. In order to find better suited bacterial and archaea candidates we will be investigating cold adapted microorganisms from astrobiologically relevant sites. Examples include the Shaban deep, a brine sediment in the Northern Red sea, permafrost core, Antarctic soil samples, glacier ice and arctic sea-ice cores. The bacteria we have selected are the following: Paenisporosarcina antarctica, Psychromonas boydii, Cryobacterium flavum, Virgibacillus arcticus and Chromohalobacter saracensis. The archaea are: Halorubrum luteum and Halorhabdus tiamatea.

The results we processed have shown that R. frigidalcoholis is more tolerant than P. halocryophilus to monochromatic UV-C (254 nm) and polychromatic UV (200-400 nm) as well as X-ray. When exposed to desiccating conditions, at different temperatures, the difference between the two organisms is not so noticeable. The results which we present here have been developed from the microorganisms grown under minimal media conditions, supplemented with a sole carbon source (L-Glutamic acid for R. frigidalcoholis and D-Alanine for P. halocryophilus). The decision to use minimal media and single carbon sources, not as common as glucose, was in support of simulating stress growth conditions to an extent similar to the ones on Europa and Enceladus. Planetary bodies where some simple organics have been detected in low concentrations.

Despite the two organisms being isolated from similar environments, R. frigidalcoholis from ice cemented permafrost in University valley (Antarctic) and P. halocryophilus from permafrost active-layer soil in the Canadian High Arctic, they have great differences in their tolerance to extreme conditions. Tested conditions include desiccation survival at: room temperature, -20 and -80°C under oxic and anoxic conditions. Additionally, we can describe a fair survival of R. frigidalcoholis to weekly freeze-thaw conditions from -80°C to 25°C respectively.

Being two organisms isolated from arctic-like environments, our hypothesis supported a great tolerance to freeze and thaw conditions. The reduction in relative survival of R. frigidalcoholis to an order of magnitude of 10^-2, supports our hypothesis. Of importance to note for this experiment are the -80°C freezing conditions. In the literature similar tests are conducted at higher temperatures (-40 and -10°C).

The preliminary results exposing R. frigidalcoholis and P. halocryophilus to harsh growth conditions are useful for initial expectations to survival in environments similar to the ones on Europa or Enceladus. For continuing and future research, this project could be of particular interest for defining a protocol for microbial exposure to simulated extreme environmental conditions. As well as to support the development of suitable planetary protection measures. The following graphs show the results of the described experiments. The figures include in formation on the relative survival of organisms and the F₁₀ values for each condition. The F₁₀ values have been included to represent the dose to which there is 10% survival to the exposed condition.

UV-C Irradiation:

Polychromatic UV Irradiation:

X-ray Irradiation:

How to cite: Zaccaria, T., Rettberg, P., Beblo-Vranesevic, K., De Jonge, M., and Netea, M.: Investigation of the physiological response of cold-adapted microorganisms to extreme environmental stress factors., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-206, https://doi.org/10.5194/epsc2022-206, 2022.

Abstract

What is life and how could it originate? This question lies at the heart of understanding the cell as the smallest living unit. Although we are witnessing a golden age of life sciences, we are ironically still far from giving a convincing answer to this question. With the aim to examines potential source of energy available to protocells on early Earth and/or elsewhere and mechanisms by which the energy could be used to drive polymer synthesis, experiments aimed at revealing the ability of meteorites and some terrestrial rocks to perform catalytic reactions operative in present-day life have been performed.

1. Indroduction 

The aim of this work is to present and discuss results of recent and ongoing wet-lab experiments supporting Multiple Root Genesis Hypothesis (MuGeRo) already proposed elsewhere [1] seeking approaches surrounding the mysterious primeval steps of life emergence on Earth or on planets around distant stars beyond our Galaxy. This is an additional hypothesis to that microbial or early forms of life were already present in our solar system at the time of our Earth’s formation so that we can reconsider that panspermia and abiogenesis are not rival theories but complementary theories [2]. Life on Earth is carbon-based, uses water as solvent, and photosynthesis and chemosynthesis as way to obtain energy. Following a bottom-up approach, I utilized as a model for the emergence of earliest life on Earth, the self-organizing M4 material that I’m producing from L6 condrites and some terrestrial rocks and minerals (olivine and magnetite ) [3].

2. Figures

[1] del Gaudio, R.: Understanding the key requirement and the conditions that sparked life on Earth and beyond:clues and new knowledges supporting MuGeRo hypothesis., Europlanet Science Congress 2020, online, https://doi.org/10.5194/epsc2020-167, 2020.

[2] del Gaudio, R.: Transition from Non-living to living Matter: can integration of MuGeRo hypothesis and synthetic prebiotic biology laboratory approach shed light on the origin of Life? , Europlanet Science Congress 2021, online, 13–24 Sep 2021, EPSC2021-347, https://doi.org/10.5194/epsc2021-347, 2021.

[3] Geraci, G., D’Argenio, B., del Gaudio R. Patent US9328337 B2, granted, 2016. 

[4] Bartlett,  S. and Wong, L., Defining Lyfe in the Universe: From Three Privileged Functions to Four Pillars Life 2020,  10(4), 42; https://doi.org/10.3390/life10040042

How to cite: del Gaudio, R.: From molecular simplicity to the emergent complexity of earliest life: investigating key features and the role of physicochemical periodic stress on Earth and on Earth-like planets., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-299, https://doi.org/10.5194/epsc2022-299, 2022.

Since the detection of the first exoplanet orbiting a star like the Sun, the University of Geneva has been at the forefront of exoplanet research. Starting from an extensive expertise in planet detection (with radial velocity), the observatory is also now an important actor in the atmosphere characterization of exoplanets (e.g. Ehrenreich et al. 2020). Today the focus is shifting towards the atmospheric characterization of small temperate planets, such as Proxima-b and the TRAPPIST-1 planets. The university is therefore actively participating to the instruments RISTRETTO@VLT and ANDES@E-ELT which aim at characterizing the atmosphere of Proxima-b (among other goals) using a technique based on high-contrast imaging and high-resolution spectroscopy. One of the objectives of these instruments is to detect biosignatures in the atmosphere of rocky temperate planets. However, to be able to correctly identify a biosignature, one needs to be able to identify false positives. So, one needs to know how the atmosphere interacts with planetary interior, with incoming stellar radiation, and with many different other processes. A multi-disciplinary approach is therefore necessary.

Recently, and following the 2019 Nobel prize in physics attributed to Michel Mayor and Didier Queloz for the discovery of 51 Peg b, the University of Geneva decided to create a faculty center: “Centre pour la Vie dans l’Univers” in French or “Center for Life in the Universe” (https://www.unige.ch/sciences/cvu/). The members of the center include experts in astrophysics, geophysics, environmental physics, chemistry, climatology and biology. The center aims at leading interdisciplinary projects on the origin of life on Earth and the search for life in our solar system and in exoplanetary systems to contribute to the world research on fundamental questions: How did life emerge and how did it diversify on Earth? Is the Universe full of life? What is the nature of life? How can we detect life elsewhere than on Earth?

Several projects are starting and will start in the near future in the center on the following topics:

• The rise of molecular complexity on primitive Earth
• Multi-stability of climates and habitability
• Evolution under extraterrestrial conditions
• The atmosphere as a mirror for geological processes

I will present these new interdisciplinary scientific projects, with an increased focus on the second and third ones which are already underway.

How to cite: Bolmont, E., Ehrenreich, D., Kasparian, J., Ibelings, B., McGinnis, D., Winssinger, N., Caricchi, L., Castelltort, S., and Mueller, A.: From experimental evolution to climate simulations: the projects of the newly created Center for Life in Universe, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-386, https://doi.org/10.5194/epsc2022-386, 2022.

Planetary protection (PP) is the scientific discipline that aims to keep the celestial bodies under study and the Earth free of biological and molecular contamination from samples that could have been brought back by space missions. Currently, this discipline is mainly focused on minimising the disturbance of planets and satellites in order to keep their environment pristine. The Committee on Space Research (COSPAR) is the body in charge of determining the good PP practices that the different space agencies must comply with [1]. These standards were developed taking into account, in particular, factors such as being located in the habitable zone, with the consequent possibility of the presence of liquid water and sufficient availability of energy on these celestial bodies. This means that the conditions of the environment could be compatible with some terrestrial microorganism, therefore, contamination could occur. For this reason, researchers from space organizations dedicated to the study of these bodies (who see contamination as a problem) should strictly follow the rules proposed by COSPAR, in order to avoid compromising future research.

This paper presents the implementation of a planetary protection protocol in a hypothetical mission launched in 2030 by a student organisation called Uvigo Spacelab [2], which currently carries out missions in orbit around the Earth that do not require a PP protocol. The 2030 mission would aim to launch a lander and a rover to explore the surface of Mars, meaning that this mission falls into the proposed category IV with COSPAR so it would require a defined PP protocol and a change in the maintenance of facilities to keep biological contamination under control.

For the elaboration of the protocol, firstly, a visit to the ESAC facilities in Madrid was carried out, in order to personally meet researchers and projects in the aerospace area. On the other hand, a visit was also made to the INTA-CAB facilities, in order to see a cleanroom dedicated to planetary protection and receive training in astrobiology and PP from experts who worked for the Raman Laser Spectrometer (RLS) project [3], with the purpose to complete and reinforce the knowledge acquired from the bibliographic resources consulted.

This learning was then applied by performing a microbiological sampling prior to the start of the mission, following a NASA sampling method, in order to quantify the accumulated bioburden in the ISO 7 cleanroom of Uvigo Spacelab. At the same time, another cleanroom with the same classification but dedicated to semiconductor and biomedical device processing at the CINTECX [4], was quantified under the same sampling method in order to compare the bioburden incorporated in the ISO 7 rooms with engineering activities. Finally, the rules and improvements to be implemented to ensure compliance with the pre-launch bioburden, which is established by the PP standards for this type of mission were drafted.

References:

[1] COSPAR Panel on Planetary Protection, 2020. COSPAR Policy on Planetary Protection. Space Res. Today 208, August 2020, Pages 10-22. https://doi.org/10.1016/j.srt.2020.07.009

[2] Rull, et al. The Raman Laser Spectrometer for the ExoMars Rover Mission to Mars. Astrobiology.Jul 2017.627-654. http://doi.org/10.1089/ast.2016.1567

[3] UVigo Spacelab: https://uvigospacelab.space/

[4] CINTECX Centro de Investigación en Tecnologías, Energía y Procesos Industriales de la Universidad de Vigo http://cintecx.uvigo.es/

Keywords: Astrobiology, Planetary Protection, Cleanrooms, COSPAR.

How to cite: Ramírez Ramos, A., Ulla Miguel, A., Cardesin-Moinelo, A., Sieiro Vázquez, C., Moral Inza, A., Chiussi, S., Berrocal Bravo, A., Aguado Agelet, F., Camanzo Mariño, A., and Briones Llorente, C.: Proposal of a preliminary Planetary Protection protocol for the development of future Mars missions at the University of Vigo., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-500, https://doi.org/10.5194/epsc2022-500, 2022.

Polycyclic aromatic hydrocarbons (PAHs) represent ~20% of cosmically available carbon [1, 2]. The further photochemical evolution of PAHs on planetary surfaces is of interest to early Earth origin-of-life studies and Mars origin-of-life speculations. Much of the literature has focused on small molecules contained in meteorites, such as amino acids and nucleic acid bases, and their potential as a carbon source for prebiotic chemistry on early Earth. However, 75% of extraterrestrial organic matter in meteorites is in aromatic form [3], and is more likely to survive the journey to a planetary surface, during which much of the small molecules can be destroyed. These stable carbon compounds could later be broken down into smaller, more biologically relevant molecules by photocatalysis on clay mineral surfaces in the ultraviolet radiation regime of early Earth and Mars.

Here we experimentally test whether PAHs degrade when adsorbed to nontronite clay and exposed to ultraviolet radiation. Experiments were performed at the INAF Observatory of Arcetri and in the PALLAS chamber at Utrecht University and were monitored with in-situ diffuse reflectance infrared spectrometry (DRIFTS) measurements. PAHs and any degradation products were extracted post-irradiation and analyzed with nuclear magnetic resonance (NMR).

[1] Allamandola, L. J., Tielens, A. G. G. M., & Barker, J. R. (1989). The Astrophysical Journal Supplement Series, 71, 733-775.

[2] Puget, J. L., & Léger, A. (1989). Annual review of astronomy and astrophysics, 27(1), 161-198.

[3] Sephton, M. A. (2002). Natural product reports, 19(3), 292-311.

How to cite: Kopacz, N., Corazzi, M. A., Poggiali, G., Camprubi-Casas, E., von Essen, A., Fornaro, T., Brucato, J., and ten Kate, I. L.: The photochemical evolution of meteoritic polycyclic aromatic hydrocarbons in clay environments on prebiotic Earth and Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-565, https://doi.org/10.5194/epsc2022-565, 2022.

Introduction

A planet that harbor water in a liquid state becomes as a study subject for its habitability evaluation. Water is the only known solvent in which the reactions for life as we know it take place, while is also a sink of molecules that include bio-essential elements such as carbon.

On Earth, oceans are reservoirs of CO₂ and CH₄ and, along with other molecules (H₂S, N₂, etc.) may be encapsulated in minerals of clathrate hydrates (thereafter clathrates) under high pressure and low temperature conditions [1]. Water molecules begin to arrange in space and join through hydrogen bonds, constructing a tridimensional crystal network that host gases inside by the van der Waals interaction forces [2]. This physical and chemical conditions required for clathrate deposits formation are found on Earth in continental margins and polar regions [3].

On Europa and Enceladus moons, clathrate deposits would not only be found in the seafloor, but also floating into oceans [4, 5, 6]. On Titan, as well as on Europa, they might form part of the composition of water-ice crust [7, 8], whereas on Ganymede and Pluto they may constitute some global layers of its internal structure [9, 10].

Clathrate formation and dissociation would play a role in geological processes and, above all, in (bio)-geochemical cycles of these planetary bodies. As clathrates are sinks of carbon and other chemical elements essential for life, the dissociation of these minerals by changes in physical chemical conditions would release gases into Europan and Enceladus´ oceans, enabling to promote favourable conditions for development of a hypothetical chemolithoautotrophic life [11]. However, gases could also be sequestrated again as carbonates or another salts due to reactions between them and rocky core in the water-rock interphase.

On Earth, encapsulated gases into clathrate structure may be metabolized by organotrophs [15] and/or by a consortium of methanotrophic archaea and sulfate-reducing bacteria after its dissociation [11, 16]. As a consequence carbonate precipitates, known as clathrite [17] because it records the past presence of these deposits. The aim of this study is to simulate the abiotic clathrite formation process under ocean-world-environmental-conditions when there are calcium saturation during clathrate formation and dissociation.

Methodology

For the experiments, we used a high-pressure simulation chamber made of stainless steel (volume capacity 67 ml) which is connected to a tank of CO₂ (gas). It is coupled with a thermocouple and pressure sensor to monitor temperature and pressure parameters and with a Raman spectrometer to analyse phase changes. We filled the high-pressure cell with crushed ice made of 7.4 wt% Ca(OH)₂ dissolution. The chamber was pressurized at 30 bar and then temperature was reduced down to 260 K. Once CO₂ clathrates were formed, the chamber was heated slowly up to 284 K. We studied the synthesis process of clathrite, taking in situ Raman spectra with a 532 nm laser at every pressure and temperature change.

Results

Carbonate precipitation occurred since CO₂ was injected to the chamber. The final product phase obtained was calcite. Nevertheless, during experiment of clathrate formation and dissociation, carbonate structure took diverse polymorphs of calcium carbonate different from pure calcite, aragonite and vaterite structures. This was evidenced by the spectral signature within the ranges of 1069.42-1087.75 cm^-1 and 709.26-731.94 cm^-1 for stretching and bending vibration of the CO₃^2- ion respectively and 150.30-160.62 cm^-1, 194.17-211.97 cm^-1 and 280.03-289.94 cm^-1 for lattice modes.

Acknowledgments

We thank project PID2019-107442RB-C32 funded by MINECO. Ana de Dios is supported by the AEI pre-doctoral contract under the project MDM-2017-0737-19-1.

References

[1] Rajput and Thakur (2016) in Geological Controls for Gas Hydrates and Unconventionals, Elsevier. [2] Sloan (1998) in Clathrate hydrates of natural gases, CRC Press. [3] Ruppel and Kessler (2017) Rev. Geophys., 55, 126-168. [4] Bouquet et al. (2015) Geophys. Res. Lett., 42, 1334-1339. [5] Prieto-Ballesteros et al. (2005) Icarus, 177, 491-505. [6] Boström et al. (2021) Astron. Astrophys. 650:A54. [7] Choukroun et al. (2010) Icarus, 205, 581-593. [8] Bouquet et al. (2019) ApJ, 855 (14). [9] Izquierdo-Ruiz et al. (2020) ACS Earth Space Chem., 4 (11), 2121-2128. [10] Kamata et al. (2019) Nat. Geosci., 12, 407-410. [11] Carrizo (2022) Astrobiology, 22 (5), DOI:10.1089/ast.2021.0036. [12] Choukroun et al. (2010) Icarus, 205, 581-593. [13] Fagents (2003) J. Geophys. Res., 108, 5139. [14] Bouquet et al. (2015) Geophys. Res. Lett., 42, 1334-1339. [15] Snyder et al. (2020) Sci. Rep., 10, 1876. [16] Bohrmann et al. (2002) Proc. Fourth Int. Conf. Gas Hydrates, Yokohama, Japan, 102-107. [17] Kennet and Fackler-Adams (2000) Geology, 28, 215-218. [18] Wehrmeister et al. (2007) J. Gemmol., 37(5/6), 269-276. [19] Eaton-Magaña et al. (2021) Minerals, 11, 177. [20] Chen et al. (2015) Chem. Eng. Sci., 138, 706-711.

How to cite: de Dios Cubillas, A., Muñoz Iglesias, V., and Prieto Ballesteros, O.: Abiotic clathrite synthesis from CO2-clathrate under ocean world conditions, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-544, https://doi.org/10.5194/epsc2022-544, 2022.

References:

[1] Bacmann A. et al (2012) A&A, 541, id.L12.

[2] Walsh C. et al. (2016) ApJL, 823.   

[3] Corazzi M. A. et al (2021) ApJ, 913.    

[4] Corazzi M. A. (2002) submitted on ApJ.

How to cite: Corazzi, M. A., Lino, V., Manini, P., and Brucato, J. R.: Photo-processing and thermal desorption of astrophysical ice mixtures on olivine grains: TPD and mass spectra analyses, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-567, https://doi.org/10.5194/epsc2022-567, 2022.

Laboratory studies of the radiation chemistry occurring in astrophysical ices have sought to better understand the dependence of this chemistry on a number of experimental parameters, such as the temperature of the ice or the energy of the incident radiation. One experimental parameter which has received significantly less attention from the research community is that of the phase of the solid ice under investigation. Our research group based at the Institute for Nuclear Research (Atomki) in Debrecen, Hungary has therefore made use of the custom-built Ice Chamber for Astrophysics-Astrochemistry (ICA) [1,2] to conduct experiments aimed at providing a better understanding of the role of the solid phase of an ice in determining the outcome of its radiation (astro)chemistry.

We have performed a series of systematic and comparative 2 keV electron irradiations of the amorphous and crystalline phases of various pure astrophysical ice analogues, including N₂O, CH₃OH, and H₂O, at 20 K [3,4]. The radiation-induced decay of these ices and the concomitant formation of products were monitored in situ using FT-IR spectroscopy. A direct comparison between the irradiated amorphous and crystalline CH₃OH ices revealed a significantly more rapid decay of the former compared to the latter. Interestingly, a significantly smaller difference was observed when comparing the decay rates of the amorphous and crystalline N₂O ices (Figure 1).

The extent of the similarity between the radiolytic decay curves of the amorphous and crystalline phases of these ices has been quantified by applying the weighted Jaccard coefficient, J_w (also sometimes referred to as the Tanimoto coefficient). This coefficient measures the similarity between two real, non-zero functions and varies between 0-1, with the 0 indicating no statistical similarity whatsoever and the 1 indicating identical functions. In the case of the radiolytic decay curves for the amorphous and crystalline CH₃OH ices, J_w = 0.40, while in the case of the investigated N₂O ices this was much higher at J_w = 0.80.

Figure 1: Electron-induced decay of CH₃OH (above) and N₂O (below) ice phases with increasing 2 keV electron fluence. Reproduced from Mifsud et al. (2022) with permission of the Royal Society of Chemistry [3].

These results have been interpreted in terms of the strength and extent of the intermolecular forces of attraction present in each molecular ice. The strong and extensive hydrogen-bonding network that exists in the crystalline CH₃OH – but not in the amorphous phase – is thought to add a significant stabilizing effect to this phase which makes it more resistant to radiation-induced decay. On the other hand, although the alignment of the molecular dipole of N₂O is expected to be more extensive in the crystalline phase, its weak attractive potential does not significantly stabilize the crystalline phase against radiation-induced decay compared to the amorphous phase as in the case of CH₃OH.

Experiments were also performed on various phases of H₂O ices using 2 keV electrons. Irradiated amorphous solid water (ASW), restrained amorphous ice (RAI), cubic crystalline ice (Ic), and cubic hexagonal ice (Ih) were found to demonstrate different responses upon the onset of electron irradiation (Figure 2). For example, the compaction of ASW ice was noted to occur fairly quickly. The ordered phases, on the other hand, all underwent amorphization as a result of their irradiation by energetic electrons. Interestingly, the amorphization of Ih was noted to require a higher electron fluence compared to those of RAI and Ic (Figure 3). This is perhaps not unexpected, as these latter phases are only meta-stable with respect to Ih.

Large variations in the appearance and shape of the mid-infrared absorption bands between the crystalline and amorphous H₂O ices made the use of the weighted Jaccard coefficient difficult and inappropriate. As such, the difference in the radiolytic decay rates of these ices was gauged indirectly by measuring the yield of H₂O₂ observed after electron irradiation of each phase. The ASW ice was found to be the most chemically productive in this way, with 0.32% of the H₂O being converted to H₂O₂. On moving to more ordered phases, however, the H₂O₂ yield was found to progressively decline, with 0.21, 0.16, and 0.14% of the H₂O being converted to H₂O₂ as a result of the irradiation of the RAI, Ic, and Ih phases, respectively.

Our results have important implications for radiative astrochemistry of interstellar and outer Solar System ices, as it is clear that the radiolytic decay and, by extension, the potential chemical productivities of these ices are greater when they are in the amorphous state rather than the crystalline phase. Given that most astrophysical ices undergo cycles of thermally induced crystallization and space radiation induced amorphization, our results suggest that the formation of new molecules (including those complex molecules of relevance to biology and the emergence of life) as a result of the processing of these ices by galactic cosmic rays, the solar wind, or giant planetary magnetospheric plasmas is most productive in those astrophysical regions where the amorphization process is more efficient. This is not an unreasonable conclusion, particularly in light of the recent spate of discoveries of complex organic molecules in the pre-stellar cloud TMC-1 [e.g., 5,6].

Figure 3: Structured H₂O stretching modes were observed to broaden as a result of electron-induced amorphization of the ices; which is suggested to be slower in the Ih phase.

The authors all gratefully acknowledge funding from the Europlanet 2024 RI which has been funded by the European Union Horizon 2020 Research Innovation Programme under grant agreement No. 871149.

References:
[1]  P. Herczku, et al. Rev. Sci. Instrum. 92, 084501 (2021)

[2]  D.V. Mifsud, et al. Eur. Phys. J. D. 75, 182 (2021)

[3]  D.V. Mifsud, et al. Phys. Chem. Chem. Phys. 24, 10974 (2022)

[4]  D.V. Mifsud, et al. Eur. Phys. J. D. 76, 87 (2022)

[5]  B.A. McGuire et al. Science 371, 1265 (2021)

[6]  K.L.K. Lee et al. Astrophys. J. Lett. 908, L11 (2021)

How to cite: Mifsud, D., Hailey, P., Herczku, P., Juhász, Z., Kovács, S., Sulik, B., Kumar Kushwaha, R., Rácz, R., Biri, S., Ioppolo, S., Kaňuchová, Z., Paripás, B., McCullough, R., and Mason, N.: The Effect of the Solid Phase Adopted by Astrophysical Ices on their Radiation Chemistry and Physics: Implications for the Synthesis of Prebiotic Molecules, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-832, https://doi.org/10.5194/epsc2022-832, 2022.

Introduction: Planets that retain a primordial, H-He dominated atmosphere can have hydrogen act as a greenhouse gas: the collision induced absorption (CIA) of infra-red light increases with pressure. This mechanism could replace regular greenhouse gasses in exoplanets to allow warm enough temperatures for a liquid water layer. Prior work[1, 2] demonstrated that either stellar insolation or intrinsic heat could be a sufficient energy source. In the case of the latter, a ‘habitable zone’ for such planets could extend up to infinity[3, 4]. In this work we aim to study the long-term potential for habitability of planets with hydrogen-dominated atmospheres. We simulate planets with varying properties to investigate how these influence the likeliness of habitable conditions. Importantly, we include for the first time long-term temporal evolution of both the planet and the host-star, to estimate how long liquid water could remain.

Methods: We model the thermal structure of a silicate-iron planet with a H-He-dominated atmosphere and vary the core mass, initial envelope mass, and semimajor-axis. An evolution model for the host-star's luminosity is included, as well as a model for the evolution of the planet's intrinsic heat and radius. The intrinsic heat model includes a radiogenic component based on Earth's abundance of radioactive materials as well as cooling and contraction of both the silicate-iron core and the gaseous envelope. We furthermore include a thermal XUV-driven atmosphere loss model. By comparing the pressure and temperature at the bottom of the atmosphere with the water phase diagram, we determine when liquid water can exist.

Results: We find that terrestrial and super-Earth planets with masses of about 1 - 10 Earth masses can maintain liquid water conditions for more than 9 billion years at radial distances larger than 2 AU. The required surface pressures are typically between ~100 bar (as on Venus) and 1 kbar (as in the oceanic trenches on Earth). Hydrodynamic escape can reduce this duration significantly for planets with a smaller envelope than 10-5 Earth mass within 10 AU, while planets with an envelope larger than 10-3 Earth mass remain mostly unaffected by this mechanism. Planets that receive a negligible amount of stellar radiation can maintain the conditions as long as the internal heat source is sufficient, which is at maximum 80 billion years in our simulation.

Conclusions: Under the assumptions of our model we show that there is a wide range of conditions under which liquid water can exist and remain on the order of 10 billion years. This raises the question whether most potentially habitable planets are very different from Earth. Our model is simplified and future work should investigate the formation and retention of a liquid water ocean in more detail. The pathway and the conditions towards planets with the right initial conditions should be studied in the future as well. This will enable us to better predict the occurence rate of such a planet and the chances of observing them at the current age of the universe.

References: [1] Stevenson D. J. (1999) Nature 400:32. [2] Pierrehumbert R. & Gaidos E. (2011). The Astrophysical Journal Letters 734:L13. [3] Seager S. (2013) Science, 340:577-581. [4] Madhusudhan, N. et al. (2021) The Astrophysical Journal, 918:1.

How to cite: Mol Lous, M., Helled, R., and Mordasini, C.: Potential long-term habitable conditions on planets with primordial H-He atmospheres., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1139, https://doi.org/10.5194/epsc2022-1139, 2022.

How to cite: Corrigan, A., Cavazzin, B., Van Mifsud, D., Hailey, P., and Mason, N.: Exploring the Prebiotic Chemistry of Europa, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1153, https://doi.org/10.5194/epsc2022-1153, 2022.

The effect of mineral surfaces on increasing molecular complexity has been considered an
important topic in studies on the origin of life [1]. In addition, HCN is considered a key molecule
in the research about the chemical evolution. Also, HCN polymers are considered keys in the
formation of the first protometabolic systems and they may be among the most readily formed
organic macromolecules in the solar system [2].
Recently, it was showed that the HCN-based polymeric films over pyrite surfaces act as
protective films. Preventing to the oxidation the high reactive pyrite surface under ambient
conditions of moisture, light an air of a standard chemistry lab. The unexpected behaviour of
the pyrite/HCN polymeric film encourages us to explore in deep these systems under early Earth
conditions due the new insight open in prebiotic chemistry [3].
Since the UV radiation can be an important factor in the increasing of the molecular complexity,
in this work the role of the protective films over pyrite surfaces were study by XPS after
irradiation of the samples during long exposure times. As a result, the formation of a film with
protective properties against corrosion by oxygen and UV radiation is identified, forming a stable
polymeric film under ambient conditions. These results raise the great potential of HCN
polymers for the development of a new class of cheap and easy-to-produce multifunctional
polymeric materials that also show promising and attractive insights into prebiotic chemistry.

1. G. Wächtershäuser, Chemistry & Biodiversity 4, 584 (2007).
2. C. N. Matthews, Origins Life Evol Biosphere 21, 421 (1991).
3. C. Pérez-Fernández, M. Ruiz-Bermejo, S. Gálvez-Martínez, and E. Mateo-Martí, RSC Advances 11, 20109 (2021).

How to cite: Pérez, C., Ruiz-Bermejo, M., Gálvez, S., and Mateo-Martí, E.: Photochemical stability and protective effect against oxidation and UV degradation of HCN polymers: an XPS study on pyrite surfaces, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1266, https://doi.org/10.5194/epsc2022-1266, 2022.