EXOA4 | Astrobiology and Origins

EXOA4

Astrobiology and Origins
Co-organized by TP
Convener: Felipe Gómez | Co-convener: Rosanna del Gaudio
Orals
| Wed, 11 Sep, 14:30–15:55 (CEST)|Room Neptune (Hörsaal D)
Posters
| Attendance Wed, 11 Sep, 10:30–12:00 (CEST) | Display Wed, 11 Sep, 08:30–19:00
Orals |
Wed, 14:30
Wed, 10:30
Astrobiology is the study of whether present or past life exists elsewhere in the universe. To understand how life can begin in space, it is essential to know what organic compounds were likely available, and how they interacted with the planetary environment. This session seeks papers that offer existing/novel theoretical models or computational works that address the chemical and environmental conditions relevant to astrobiology on terrestrial planets/moons or ocean worlds, along with other theoretical, experimental, and observational works related to the emergence and development of Life in the Universe. This includes work related to prebiotic chemistry, the chemistry of early life, the biogeochemistry of life’s interaction with its environment, chemistry associated with biosignatures and their false positives, and chemistry pertinent to conditions that could possibly harbor life (e.g. Titan, Enceladus, Europa, TRAPPIST-1, habitable exoplanets, etc.).
Understanding how the planetary environment has influenced the evolution of life and how biological processes have changed the environment is an essential part of any study of the origin and search for signs of life. A central issue in the research on the emergence of life is the paradoxical role of water in pre-biotic chemistry. In fact,on the one hand, water is essential for all known life, on the other hand it is highly destructive for key biomolecules such as nucleic and polypeptides. Earth analogues experiments/instruments test and/or simulation campaigns and limits of life studies are included as well as one of the main topics of this session.

Major Space Agencies identified planetary habitability and the search for evidence of life as a key component of their scientific missions in the next two decades. The development of instrumentation and technology to support the search for complex organic molecules/sings of life/biosignatures and the endurance of life in space environments is critical to define unambiguous approaches to life detection over a broad range of planetary environments. A truly interdisciplinary approach is needed to delve into the core of the issue of emergence of life, because in addition to physics and chemistry it is also need to deploy a number of other sciences. We rely on contribution coming from mathematical or philosophical perspectives not only on astrobiology moreover we think that a part of the answers may lie in scientists who working on cancer research, genetics, space exploration paleontology who are not necessarily involved in this field.

Orals: Wed, 11 Sep | Room Neptune (Hörsaal D)

Chairpersons: Felipe Gómez, Rosanna del Gaudio
14:30–14:40
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EPSC2024-152
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ECP
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Virtual presentation
Thomas Matreux, Paula Aikkila, Almuth Schmid, Dieter Braun, and Christof B. Mast

Life is an out-of-equilibrium process, pointing towards an emergence that must also have been decisively shaped and driven by the non-equilibrium systems present 4 billion years ago. Rocks and their constituent phases likely played an essential role as molecular feedstock. We aim to combine this geological scenario with physical non-equilibria such as thermal gradients, offering unique opportunities for molecular selection.

We have studied how simple heat flows through geological networks of interconnected chambers create chemical niches with complex mixtures of prebiotically relevant substances, each with different concentration ratios (1). These confined spaces could thus enable various prebiotic reactions and boost their yield and selectivity compared to bulk systems. We show this exemplarily with the trimetaphosphate-driven dimerization of glycine. Trimetaphosphate, presumably rare on the early Earth, experiences strong thermophoresis and is accumulated significantly stronger than for instance glycine, increasing product yields by multiple orders of magnitude.

Prebiotic reactions often require a defined set of ion concentrations. One example is the activity of some important RNA enzymes that vanishes without divalent magnesium salt, whereas an excess of monovalent sodium salt reduces enzyme function. However, leaching experiments show that relevant geomaterials such as basalts release mainly sodium and only little magnesium. In heated rock cracks, the superposition of convection and thermophoresis actively enriches magnesium ions against sodium and establishes a habitat for ribozyme function from basaltic leachates (2). Interestingly, the same process can also solubilize one of the most abundant phosphate minerals on the early Earth, Apatite, by fractionation of its acidic-dissolved constituents.Under pH conditions relevant to nascent life, this leaves up to 15 mM of phosphate in solution, facilitating the formation of condensed, more reactive phosphate species.

References

(1) Matreux, T., Aikkila, P., Scheu, B., Braun, D. & Mast, C. B. Heat flows enrich prebiotic building blocks and enhance their reactivity. Nature 628, 110–116 (2024).

(2) Matreux, T. Le Vay, K., et al. Heat flows in rock cracks naturally optimize salt compositions for ribozymes. Nat. Chem. 13, 1038–1045 (2021).

How to cite: Matreux, T., Aikkila, P., Schmid, A., Braun, D., and Mast, C. B.: Geothermal non-equilibria as prebiotic selector, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-152, https://doi.org/10.5194/epsc2024-152, 2024.

14:40–14:50
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EPSC2024-200
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ECP
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On-site presentation
Fuencisla Cañadas Blasco, Romain Guilbaud, Philip Fralick, Yijun Xiong, Simon W. Poulton, Mari-Paz Martin Redondo, and Alberto G. Fairén

Investigating the presence of oxygen on planets within our solar system and beyond is crucial for understanding the potential for life beyond Earth. Oxygen is a key ingredient for life as we know it and serves as a key indicator of habitability and planetary processes [1]. On Earth, the first lasting rise in atmospheric oxygen started ∼2.4 billion years ago and was a crucial process that fundamentally transformed the planet's atmosphere and oceans, leading to the evolution of complex life forms. However, geochemical evidence reveals the existence of intermittent oxic whiffs before that period, although the mechanisms that drove the production of such early oxygen are poorly constrained. Here, we present redox sensitive trace metal and Fe speciation data, as well as phosphorus phase partitioning results, for a 2.94 billion-year-old drill core from the Red Lake area, Canada. Results suggest dynamic oceanic Fe cycling between ferruginous conditions (anoxic Fe-rich), euxinic (anoxic S-rich) and short-lived episodes of oxygenated waters consistent with depleted (<1) Enrichment Factors (EFs) for Vanadium, Molybdenum and Uranium. The sources of oxygen on early Earth are still debated, but the presence of a wide range of stromatolites (sedimentary structures formed by photosynthetic organisms) in the studied area [2-3] points to cyanobacterial photosynthesis as the principal source of oxygen [2], which accumulated in protected shallow areas, unveiling one of the earliest oxic whiffs which predates global atmospheric oxygen accumulation by ∼500 Ma. 

The intervals of the drill core described as deposited under oxic water conditions are characterized by pulsed increases in oceanic P concentrations, primarily in the form of authigenic P, and elevated Corg/Porg ratios relative to the Redfield ratio (the molar ratio of C and P in phytoplankton at C:P = 106:1). These results are indicative of preferential release of P during the remineralization of organic matter [4]. To determine whether this P was recycled to the water column or fixed in the sediment, we compare Corg/Preac ratios, where Preac= Pauth + PFe + Porg. The results also reveal variable Corg/Preac ratios which indicate alternating periods of limited recycling, with efficient P fixation in the sediment in association with Fe minerals, and enhanced P recycling to the water column. Interestingly, the intervals of enhanced P recycling are characterized by elevated sulfide content. This condition leads to the dissolution of Fe minerals, releasing sequestered P, and the selective liberation of P from organic matter during bacterial sulfate reduction [4]. Consequently, substantial P fluxes are reintroduced to the water column, potentially promoting photosynthetic primary productivity, a hypothesis substantiated by the presence of stromatolites. This, in turn, may have intensified organic carbon burial, contributing to incipient ocean episodic oxygenation during the Archean. 

Paleoenvironmental reconstructions of early Earth play a key role in unravelling the co-evolution of life and the Earth system. Our understanding of the biogeochemical evolution of the P cycle during the Archean holds the potential to provide insights into environments—on Earth or other terrestrial planets—where sufficient dissolved P could have accumulated. Such systems may have been conducive to the emergence and evolution of life, offering valuable perspectives on the conditions necessary for life's development.

References: 

[1] Cockell et al., (2016) Astrobiology, 16, 1. [2] Fralick, P. & Riding, R. (2015) Earth-Science Rev., 151, 132–175. [3] Afroz M. et al., (2023) Precambrian Research, 388, 106996. [4] Ingall et al., (1993) Geochimica et Cosmochimica Acta, 57, 303-316. 

How to cite: Cañadas Blasco, F., Guilbaud, R., Fralick, P., Xiong, Y., Poulton, S. W., Martin Redondo, M.-P., and G. Fairén, A.:  Life-Earth coevolution: the role of phosphorus in Archean oxygen accumulation , Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-200, https://doi.org/10.5194/epsc2024-200, 2024.

14:50–15:00
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EPSC2024-962
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ECP
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On-site presentation
Lucas Bourmancé, Elisa Ravaro, Maud Toupet, Ruben Nitsche, Sebastien Brûle, Bertrand Raynal, Andreas Elsaesser, and Adrienne Kish

High salt environments are ubiquitous in the solar system (Earth, Mars, Enceladus, Europa). As life on our planet is the only life we know of, terrestrial salt-loving (halophilic) microorganisms can be used to better characterize how life can thrive in such conditions. Halophilic archaea from the genus Halobacterium have been preserved in the fluid inclusions of halite crystals (NaCl) (Jaakkola et al., 2016). Hence, fluids inclusions may hold preserved biomolecules acting as ancient life biosignatures. Halites represent great exobiological interest as they have been identified on Mars (Osterloo, M. M. et al., 2008; Bramble & Hand, 2024).

Membrane lipids has already been described as good candidates for biosignatures because of their long-term stability properties (Georgiou & Deamer, 2014) and membrane proteins, even though more fragile biomolecules, might be better preserved in high salt conditions.

Therefore, this project aimed at understanding how Hbt. salinarum cell envelope fragments, produced by cell lysis, respond to UV irradiation (>185 nm) when incubated in different fluid inclusion compositions using a ground-based solar simulator. Fluid inclusions compositions were selected to represent Early Earth and Mars environments as well as modern Earth.

High salt conditions are rarely compatible with traditional biochemistry methods and extensive optimization work is needed to render them suitable for the analysis of evaporite samples. For this project, this included optimization of cell envelope and membrane protein extractions, UV radiation exposure and investigating adequate methods for structural analysis.   

The chaotropic/kosmotropic effects of the brines on the structural stability of proteins and lipids of the cell envelope were determined using nano-Differential Scanning Fluorometry, Differential Scanning Calorimetry and Analytical Ultracentrifugation. In addition, a label-free mass spectrometry approach was employed to assess chemical modifications of membrane proteins (Orbitrap nano-LC-MS/MS) and lipids (GC-MS) after exposure to the different brines and radiation treatments. Finally, the photochemistry of the brines was investigated by looking at reactive oxygen species production using a fluorescent probe.

This project has shown that certain brine ionic compositions are more prone to support cell envelope biosignature preservation against UV irradiation due to a combination of specific photochemistry and chaotropic effects. This work allows for the screening of various new methods for compatibility with high salts environment biochemistry required for analog studies on Earth but also for future analysis of space returned samples.

The results of these ground-based experiments will be compared to real space irradiation as cell envelope samples will be exposed outside the International Space Station as part of the Exocube space experiment.

This work was financed by the ANR ExocubeHALO ANR-21-CE49-0017-01 grant to A.Kish.

 References:

  • Bramble, M. S., & Hand, K. P. (2024). Spectral evidence for irradiated halite on Mars. Scientific Reports, 14(1). https://doi.org/10.1038/s41598-024-55979-6
  • Georgiou, C. D., & Deamer, D. W. (2014). Lipids as universal biomarkers of extraterrestrial life. In Astrobiology (Vol. 14, Issue 6, pp. 541–549). Mary Ann Liebert Inc. https://doi.org/10.1089/ast.2013.1134
  • Jaakkola, S. T., Ravantti, J. J., Oksanen, H. M., & Bamford, D. H. (2016). Buried Alive: Microbes from Ancient Halite. In Trends in Microbiology (Vol. 24, Issue 2, pp. 148–160). Elsevier Ltd. https://doi.org/10.1016/j.tim.2015.12.002
  • M. Osterloo et al. (2008), Chloride-Bearing Materials in the Southern Highlands of Mars, Science 319, 1651, DOI: 10.1126/science.1150690

 

 

How to cite: Bourmancé, L., Ravaro, E., Toupet, M., Nitsche, R., Brûle, S., Raynal, B., Elsaesser, A., and Kish, A.: Influence of salts on the preservation of microbial cell surface biosignatures exposed to UV radiation, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-962, https://doi.org/10.5194/epsc2024-962, 2024.

15:00–15:10
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EPSC2024-205
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On-site presentation
Isabel Herreros and David Hochberg

INTRODUCTION
The chemistry of life on Earth is based on a basic asymmetry of certain molecules whose threedimensional geometrical structure or conformation is not identical to that of their mirror image, or spatial reflection through a mirror. Parity P, or space inversion, a discrete spatial symmetry transformation of fundamental physics, is broken at the molecular level. Such molecules are said to possess chirality or handedness. The mirror image structures of a chiral molecule are called enantiomers. Homochirality is ubiquitous in biological chemistry from its very start. Amino acids, the building blocks of proteins, and the sugar backbones present in DNA and RNA, are chiral molecules. The origin of biological homochirality has intrigued the scientific community ever since its initial discovery by Pasteur. To unravel its possible origin, we have conducted a combined theoretical and numerical study on the physics of fluid flows in curved pipes. In such coiled ducts, hydrodynamic flows develop a net chirality which can then be transmitted, via viscous shear forces, to the level of molecular self-assembly. This establishes a purely fluid-mechanical mechanism of mirror symmetry breaking from the fluid flow to the constituent molecules [1].

CHIRAL SYMMETRY BREAKING IN HELICAL FLOWS
Let us consider a set of curved pipes with circular section of radius r and radius of curvature R. In order to avoid dimensional bias, dimensionless quantities are considered for the definition of the flow regime: curvature=r/R, pitch=h/R, Re=rρU/μ (Reynolds number) and De=Re√(r/R) (Dean number), where ρ is the density of the fluid, μ the dynamic viscosity, U the flow velocity in the pipe’s centerline direction and h the length of the helical pitch. In the case of toroidal pipes (pitch=0), the cross-sectional secondary flow consists of two symmetric recirculating regions.

However, when the pipe is subjected to a pitch, i.e. in the case of helical pipes, an asymmetric vortex pair structure is generated. This hydrodynamic shear flow asymmetry might then induce chiral symmetry breaking at the molecular level (top-down chirality transfer).

To quantify the symmetry breaking of the cross-sectional vortex pair in helical pipes, a set of numerical tests is carried out [2]. The input consists of the physical flow conditions: Reynolds number, Re, which accounts for the main flow velocity and fluid properties (density and viscosity) along with the geometric properties (curvature, r/R, and pitch, h/R).

When the pipe is subjected to a pitch, i.e. in the case of helical pipes, an asymmetric vortex pair structure is generated. This hydrodynamic shear flow asymmetry might then induce chiral symmetry breaking at the molecular level (top-down chirality transfer).

 

MODEL RESULTS
The model presented allows the quantification of the chiral symmetry breaking in a helical flow reactor by means of the chiral parameter, χ = χ(De, pitch), given by the following mathematical expression:

where a and b are functions of the dimensionless helical pitch=h/R:

These results are extremely useful to determine the geometric characteristics and operating conditions for the design of an experimental helical flow reactor, in order to control the net chirality of the outflow, leading to numerous important applications in both basic and applied science [4,5], and in origin-of-life scenarios under the influence of fluid flow [6].

REFERENCES
[1] Ribó et al., Science, 292 (5524): 2063-2066 (2001)
[2] Herreros and Hochberg, Physics of Fluids, 35: 043614 (2023)
[3] Herreros and Ligüérzana, Physics of Fluids, 32: 123311 (2020)
[4] Sevim et al., Nat. Commun., 13: 1766 (2022)
[5] Sun et al., Nat. Commun., 9: 2599 (2018)
[6] Brandenburg and Hochberg, Orig. Life Evol. Biosph. 52: 1–2 (2022)


ACKNOWLEDGEMENTS
This research has been funded by grant No. PID2020-116846GB-C22 by the Spanish Ministry of Science and Innovation/State Agency of Research MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. Thanks to Josep M. Ribó for many insightful discussions. I.H. would like to express her gratitude for the years of scientific collaboration with the late David Hochberg, who is deeply mourned by family, friends, and colleagues.

How to cite: Herreros, I. and Hochberg, D.: Chiral vortices in fluids and spontaneous mirror symmetry breaking, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-205, https://doi.org/10.5194/epsc2024-205, 2024.

15:10–15:15
15:15–15:25
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EPSC2024-393
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ECP
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On-site presentation
Lorenzo Biasiotti, Paolo Simonetti, Giovanni Vladilo, Stavro Ivanovski, Mario Damasso, Alessandro Sozzetti, and Sergio Monai

Introduction:  The recently discovered super-Earth planet Gl 514 b, orbiting the nearby (7.6 pc, [1]) M-dwarf, is an interesting case to explore the habitability of planets that radically differ from the Earth. Habitability studies often rely on the classic definition of the Habitable Zone (HZ), and in particular on the so-called Conservative Habitable Zone (CHZ, [2]). Due to the combination of its relatively large semi-major axis (a=0.42 AU) and eccentricity (e=0.45), Gl 514b lies part of the time inside the CHZ (about 34% of the orbital period) and the rest of the time beyond the outer edge of the CHZ. This suggests the presence of strong seasonal variations that impact the actual habitability of the planet. Tracking the seasonal evolution of habitability is not possible using the HZ approach and requires the application of seasonal climate models tailored for specific stellar, orbital and planetary parameters.

 

Investigating the potential climates of planets that exhibit seasonal episodes of habitability is intriguing because it could provide insights into the dynamic nature of planetary systems and the potential for the support of life in exotic scenarios. In this sense, the study of the habitability of Gl 514 b can be generalized to all that cases in which there are strong instellation variations, thus helping to define a “Seasonal Habitable Zone”.

 

The Model: In our study we use the climate model, EOS-ESTM [3,4] for exploring the habitability of Gl 514 b by calculating an index of surface habitability based on the surface temperature distribution. In practice, we explore the habitability as a function of climate factors currently unconstrained by the observations (e.g., Fig 1), such as the ocean cover fraction, the obliquity, and the atmospheric composition. We consider three different types of atmospheres: (i) CO2-dominated, (ii) CO2 + 0.1% CH4 and (iii) CO2 + 1.0% CH4.

Since transits of Gl 514 b have not been detected so far, we estimate the radius and the surface gravity from interior structure models (e.g. [5]) and from the measurements of the minimum mass (5.2 M). The high eccentricity of Gl 514 b suggests that the system is dynamically young and that spin-orbit tidal synchronization may not have yet occurred (e.g. [6]). Assuming that the planet is not tidally locked, in this contribution we present results obtained for a rotation of 1 day (see full paper for complete set of tests).

 

Results: In the present work, we show how the habitability of Gl 514b is impacted by different combinations of planetary, orbital and atmospheric parameters. The impact of the ocean cover fraction is significant due to the orbit of Gl 514 b (see Figure 1). In fact, the large thermal capacity of even a 25-m shallow ocean provides sufficient thermal inertia to avoid freezing conditions near apoastron. Similarly, the obliquity plays a fundamental role in seasonal habitable events. The higher the obliquity of the planet, the greater the thermal excursion to the poles is (see Figure 2). Nonetheless, we show that these effects are regulated by the total surface pressure and the content of methane in the atmosphere. We present results of the parameter space that allows conditions of continuous and transient habitability. 

 

Figure 1. Predicted values of the habitability index, ℎ, as a function of the ocean cover fraction and total surface pressure for three different atmospheric

compositions. Left panel: CO2-dominated; middle panel: CO2+ 0.1% CH4; right panel: CO2+ 1% CH4. For the remaining parameters we adopt 𝜖 =23.44◦,

𝑃𝑟𝑜𝑡 =1 day and 𝜔𝑝𝑒𝑟𝑖 =0◦. The dashed areas indicate the parameter space in which atmospheric CO2 condensates.