Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022
EXOA15
Habitability and biosignatures for the search for life in our Solar system

EXOA15

Our search for life on our neighboring planets and moons is guided by increasing our knowledge on terrestrial life’s survivability and adaptability and on our capacity to detect its traces. On one hand, extremophilic organisms of all domains of life have shown us extraordinary adaptations strategies in colonizing Earth’s most inhospitable environments and their study has far reaching implications not only for astrobiology research but also in different fields such as ecology, molecular and cellular biology, physiology, and biotechnology. On the other hand, each planetary target presents unique environments and conditions that could enhance or decrease biosignatures’ preservation and therefore their detectability by in situ, sample return, or remote measurements. Studies from field analogs, laboratory, simulation and space experiments or theoretical investigations can greatly support and guide current and future missions dedicated to search for life and its traces. Experiments on space platforms and missions, for instance, allow the exposure of biological and chemical samples to unique outer space conditions but require special hardware developments of high interest for astrobiology and related fields.

Conveners: Mickael Baqué, Frédéric Foucher, Ruth-Sophie Taubner, Rosa de la Torre Noetzel, Alex Price, Silvana Pinna, Hector-Andreas Stavrakakis | Co-conveners: Kensei Kobayashi, Petra Rettberg, Jean-Pierre Paul de Vera, Daniela Billi, Lena Noack, Barbara Cavalazzi, Séverine Robert
Orals
| Fri, 23 Sep, 15:30–18:30 (CEST)|Room Manuel de Falla
Posters
| Attendance Thu, 22 Sep, 18:45–20:15 (CEST) | Display Wed, 21 Sep, 14:00–Fri, 23 Sep, 16:00|Poster area Level 2

Session assets

Discussion on Slack

Orals: Fri, 23 Sep | Room Manuel de Falla

Chairpersons: Silvana Pinna, Ruth-Sophie Taubner
15:30–15:50
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EPSC2022-187
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solicited
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MI
Frances Westall, Laura Clodore, Frédéric Foucher, Tetyana Milojevic, Denise Kölbl, Pamela Guérillot, Keyron Hickman-Lewis, Barbara Cavalazzi, and Jorge Vago

Two missions are on Mars looking for traces of life (MSL and Mars 2020) while the ExoMars mission, slated for launch later this year, is postponed. All missions are equipped with a powerful array of instrumentation for in situ analyses. In addition, the ExoMars rover, Rosalind Franklin, has the advantage of a 2 m drill to penetrate beneath the oxidised and UV-irradiated surface [1]. However, unless phototrophic life forms were able to develop on a planet that was never permanently habitable and that was characterised by punctuated and likely unconnected habitable niches [2, 3], martian life likely remained in a very primitive state of evolution, potentially similar to terrestrial chemotrophs, i.e. discrete, very small cells and colonies that leave even more subtle fossil remains. Indeed, only in the vicinity of nutrient-rich hydrothermal environments can chemotrophic biomass develop to create potentially visible morphological signatures in the form of a clotted texture in the associated sediments – a texture that is not immediately identifiable as a biosignature but that would warrant further analysis of such rocks by other instruments, such as SAM on Curiosity, SHERLOC on Perseverance, or MOMA on Rosalind Franklin.

Taking the early terrestrial environment and early life as analogues for habitable environments and primitive life forms on early Mars, it is becoming clearer that the most primitive of life forms known on Earth, chemolithotrophs that obtain energy from oxidation of inorganic substrates (e.g. ferrous iron, hydrogen sulfide, elemental sulfur, thiosulfate, or ammonia), were widely distributed but, because of their very small size (< 1 µm diameter) and very small, heterogeneously distributed colonies (5 µm to some tens of microns), are typically undetectable through bulk analyses (bulk carbon contents are generally 0.01-0.05 %.) (Fig. 1). To compound the challenge, morphologically-recognisable cells are rarely observed, while degraded cells mixed with generic extracellular polymeric substances (EPS) are more frequent. Chemolithotrophs can inhabit sediment particle surfaces and pore space close to the surface or at depth, as long as they have access to nutrients and water. But how to identify them in situ on Mars? Even on Earth with well-equipped, state of the art laboratories, detection and identification of fossil chemolithotrophs is difficult and, often, controversial. The solution requires seeking to simultaneously detect structural information of the organisms’ presence and analyse well-preserved organogeochemical signature with spatial precisions on the order of a micron and detection limits as low as possible. This would be a challenge for Mars Sample Return in the near future.

Figure 1. (A-C) distribution of tiny colonies and EPS clumps (red circles) in a silicified, volcanic sediment [3] at increasing magnifications. Individual dividing cells visible only at maximum resolution in (C).

References: [1] Vago, J.L., et al. (2017) Astrobiology, 17: 471–510. [2] Cockell et al., 2012. Icarus, 217:184–193. [3] Westall et al., (2015) Astrobiology, 17: 998-1029. [4] Author J. et al. (2002) LPS XXXIII, Abstract #2110.

How to cite: Westall, F., Clodore, L., Foucher, F., Milojevic, T., Kölbl, D., Guérillot, P., Hickman-Lewis, K., Cavalazzi, B., and Vago, J.: The search for extraterrestrial life and the problem of primitive life forms, now you see them, now you don’t, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-187, https://doi.org/10.5194/epsc2022-187, 2022.

15:50–16:00
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EPSC2022-1195
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ECP
Lorenzo Biasiotti, Paolo Simonetti, Giovanni Vladilo, Laura Silva, Giuseppe Murante, Stavro Ivanovski, Michele Maris, Sergio Monai, Erica Bisesi, and Jost von Hardenberg

INTRODUCTION

Over the past two decades, ground- and space-based observations have unveiled thousands exoplanets and planetary systems around other stars in our Galaxy. About 5000 exoplanets are currently confirmed, in large part detected as transits by the Kepler and TESS missions. Launched in 2019, PLATO mission represents the first-step characterisation towards the understanding of the structural properties of these planets. Nevertheless, a significant boost for the detection of transiting Earth-analogues around bright stars is expected from the PLATO mission. 
However, it's only through remote atmospheric spectroscopy of potentially habitable rocky planets, that one of the main goals of exoplanetary science, the quest for life outside the Solar System, can be tackled. This observational challenge should be partly within reach of the recently launched JWST and the next ground-based astronomical observatory, E-ELT.

To accomplish the demanding task of searching for and  deciphering spectral signatures, a thorough and holistic observational and theoretical characterization of carefully selected rocky exoplanets is required.
The selection, among the observationally reachable targets for high-resolution spectroscopy of thin atmospheres, requires habitability studies with climate models. 
These simulations will enable the identification of those exoplanets with the largest chance of potentially hosting a surface diffuse life, i.e. with the largest habitability, that must be evaluated over a wide range of mostly unknown conditions. 
A considerable effort of modelization that exploits all available observations will be needed in order to assess the global physical characterization of the selected exoplanets, and in particular precisely of their potential surface climate and habitability.

 

THE MODEL

Here we present EOS-ESTM, a flexible climate model aimed at simulating the surface and atmospheric conditions that characterize habitable planets. The model allows one to perform a fast exploration of the parameter space representative of planetary quantities, including those currently not measurable in rocky exoplanets. EOS-ESTM has been built up starting from ESTM (Vladilo et al. 2013, 2015), a seasonal-latitudinal EBM featuring an advanced treatment of surface and cloud components and a 2D (vertical and latitudinal) treatment of the energy transport.

The main features of the model that we have implemented can be summarised as follows.

Firstly, we have calculated the atmospheric radiative transfer using EOS (Simonetti et al. 2022), a procedure tailored for atmospheres of terrestrial-type planets, based on the opacity calculator HELIOS-K (Grimm & Heng 2015; Grimm et al. 2021) and the radiative transfer code HELIOS (Malik et al. 2017, 2019). Thanks to EOS, the ESTM radiative transfer can be now calculated for a variety of atmospheres with different bulk and greenhouse compositions, illuminated by stars with different SEDs.

Then, we have upgraded the parameterizations that describe the clouds properties. New equations have been introduced for the albedo of the clouds and its dependence on the albedo of the underlying surface. The clouds coverage over ice is now a function of the global planetary ice coverage. A specific treatment for the transmittance and OLR forcing of clouds at very low temperature has been introduced.

Lastly, we have introduced a generalized logistic function to estimate the ice coverage as a function of mean zonal surface temperature. Based on a detailed study of the ice distribution on Earth, the adopted algorithm discriminates between ice over lands and oceans. The albedo and thermal capacity of transitional ice is now estimated using the fractional ice coverage. 


RESULTS

With the aim of providing a reference model for studies of habitable planets, we calibrated EOS-ESTM using a large set of Earth satellite and reanalysis data.  
The reference Earth model satisfies a variety of diagnostic tests, including mean latitudinal profiles of surface temperature (Figure 1), TOA albedo, OLR and ice coverage.

Fig. 1. Mean annual latitude profile of surface temperature predicted by the reference Earth model The temperature profile is compared with ERA5 temperatures averaged in the period 2005-2015 (blue dots).

To test the consistency of EOS-ESTM with previous studies of non-terrestrial climate conditions we performed a series of comparisons with a hierarchy of climate models, varying the levels of insolation (Figure 2), the stellar spectrum and planetary parameters (radius and rotation rate).

Fig. 2. Comparison of global and annual  mean surface temperature obtained from different climate Earth's models by increasing the solar constant. Red, solid line: EOS-ESTM (this work). Black, solid line: 3D model CAM4 (Wolf & Toon, 2015). Cyan, solid line: 3D model CAM3 (Wolf & Toon, 2014). Green, solid line: 3D model by Leconte et al. (2013).

The application of EOS-ESTM to the case of a CO2-dominated atmosphere in maximum greenhouse conditions (Kasting et al. 1993) yields a detailed description of the transition to a snowball state that takes place when the insolation decreases in the proximity of the outer edge of the HZ. Thanks to the flexibility of our model we can explore how this transition develops in different planetary conditions (e.g. rotation rate, Figure 3).

Fig. 3. Dependence on planetary rotation period rotation period, Prot, of the fractional ice coverage calculated at the outer edge of the HZ. The results were obtained for an Earth-like planet with a CO2-dominated, maximum greenhouse atmosphere, the remaining parameters being fixed to Earth values.

 

REFERENCES

Grimm S. L., Heng K., 2015, HELIOS-K: Opacity Calculator for Radiative Transfer (ascl:1503.004)

Grimm S. L., et al., 2021, ApJS, 253, 30

Kasting J. F., Whitmire D. P., Reynolds R. T., 1993, Icarus, 101, 108

Leconte J., Forget F., Charnay B., Wordsworth R., Pottier A., 2013, Nature, 504, 268

Malik M., et al., 2017, AJ, 153, 56

Malik M., Kitzmann D., Mendonça J. M., Grimm S. L., Marleau G.-D., Linder E. F., Tsai S.-M., Heng K., 2019, AJ, 157, 170

Simonetti P., Vladilo G., Silva L., Maris M., Ivanovski S. L., Biasiotti L., Malik M., von Hardenberg J., 2022, ApJ, 925, 105

Vladilo G., Murante G., Silva L., Provenzale A., Ferri G., Ragazzini G., 2013, ApJ, 767, 65

Vladilo G., Silva L., Murante G., Filippi L., Provenzale A., 2015, ApJ, 804,50

Wolf E. T., Toon O. B., 2014, Geophys. Res. Lett., 41, 167

Wolf E. T., Toon O. B., 2015, Journal of Geophysical Research (Atmospheres), 120, 5775

How to cite: Biasiotti, L., Simonetti, P., Vladilo, G., Silva, L., Murante, G., Ivanovski, S., Maris, M., Monai, S., Bisesi, E., and von Hardenberg, J.: EOS-ESTM: a flexible climate model for habitable exoplanets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1195, https://doi.org/10.5194/epsc2022-1195, 2022.

16:00–16:10
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EPSC2022-378
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ECP
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Jaume Puig, Nastassia Knödlseder, Jaume Quera, Manuel Algara, and Marc Güell

Some organisms have shown to be able to naturally survive environments which we consider extreme, including the Low Earth Orbit, or even Outer Space. These microorganisms have natural mechanisms to repair severe DNA damage, such as the caused by ionizing and non-ionizing radiation or extreme temperatures and pressures. Some examples are Deinococcus radiodurans, which proved to be capable of surviving in the Exposure Facility of the International Space Station (ISS) for up to three years, and tardigrade species, such as Ramazzottius varieornatus, which are some of the most resilient known organisms. In this study, performed at the Barcelona Biomedical Research Park in collaboration with Hospital del Mar, survival under simulated Low Earth Orbit environmental conditions was tested in engineered and wild-type Escherichia coli strains. Ionizing radiation resistance was enhanced by transforming the Dsup gene from R. varieornatus and two genes from D. radiodurans involved in DNA damage repair, RecA and uvrD. This enhancement, together with a directed evolution process, resulted in a significant increase in the surviving fraction of the E. coli strain protected with the Dsup gene after a high dose, up to 3000 Gy, of ionizing radiation exposure in the form of a continuous spectrum of X-ray photons. Additionally, the survival to wide ranges of temperatures and low pressures was tested for the same strains, revealing a lack of relevance of cell aggregation for survival under the mentioned conditions in contrast with the case of D. radiodurans. However, survival rates showed no enhancement for any of the new E. coli strains. In a new collaboration with the Subterranean Laboratory of Canfranc, both the absence of radiation and extreme levels of radiation will be further studied. Additionally, an extreme environments analogue for several environmental conditions will be built, allowing for more specific testing on a controlled environment. This research represents a first step in the creation of new bacterial strains engineered to survive severe conditions and adapting existing species for their survival in remote environments, like extra-terrestrial habitats. These species could pave the road for future human expeditions, helping develop environments hospitable to life. In addition, studying the efficacy and the functioning of the genetic mechanisms used in this study could be beneficial for fields such as ecological restoration and medical and life sciences engineering, addressing treatments and/or diseases caused or related to radiation and DNA damage. Space is believed to be the last frontier, but the truth is, we are still a frontier to ourselves.

How to cite: Puig, J., Knödlseder, N., Quera, J., Algara, M., and Güell, M.: DNA Damage Protection for Enhanced Bacterial Survival Under Simulated Low Earth Orbit Environmental Conditions in Escherichia coli, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-378, https://doi.org/10.5194/epsc2022-378, 2022.

16:10–16:20
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EPSC2022-962
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MI
The IR-COASTER project for Astrobiology experiments outside the International Space Station or as a payload for 6U Cubesats
(withdrawn)
fabien stalport, hervé cottin, noel grand, anais feron, cecile gaimoz, mathieu Gourichon, kristian harge, xavier landsheere, ines louison, florent mignon, sylvain triquet, lisa viallon, pascal zapf, isabelle savin de larclause, didier chaput, and christian mustin
16:20–16:40
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EPSC2022-1055
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solicited
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MI
Rosa de la Torre Noetzel, Olga Bassy Alvarez, Maria Victoria Ortega-García, Leopoldo García Sancho, Adela Villasante, Javier del Olmo, Jean Pierre de Vera, and Raul Herranz

The search for extraterrestrial life and finding habitable environments on other planets and satellites like Mars, Europa, Enceladus and Titan are a priority of NASA and ESA, since the last decade. To contribute to these highly significant challenges, research has been done with established exposure platforms like those on the Foton satellite and EXPOSE on the ISS expanding now to ESA’s platform Bartolomeo. These were used to expose samples to space vacuum and space radiation, but also to provide gas supply and selected planetary radiation environments. Results obtained by these experiments have allowed to get supplemental knowledge necessary for supporting future investigations to search for life in the universe.

Several extremophile lichen species, have been exposed to extraterrestrial environments, i.e. space- and Mars like parameters, during short and long periods on board of ESA’s space missions (Foton M2 and M3, EXPOSE E and R2) to investigate the limits of terrestrial life. To maximize the scientific outcome of these experiments, LICHENS [1], LITHOPANSPERMIA [2], LIFE [3], and BIOMEX [4], a common elaboration and analysis of the results obtained on analogue field studies with results obtained in planetary simulation facilities was necessary to check the survival potential and vitality of the samples before flight. Tests and experiments at different simulation facilities at DLR, and at INTA, included the exposure to space vacuum, space UV radiation and space cosmic radiation, and to Mars-like environment, i.e. Mars atmospheric composition and pressure, as well as Mars UV radiation. Not microgravity or reduced gravity, which is present in space and on Mars, was tried.

Here we show the results of the resistance of two extremophile vagrant lichen species, Xanthoparmelia hueana and Circinaria gyrosa, to simulated microgravity (rotation speed of clinostate: 1 rpm) using the UNZIP clinostate at CIB-CSIC (Centro Investigaciones Biológicas Margarita Salas). This is the first time that lichens will be exposed to weightlessness environment in an attempt to isolate the potential contribution of microgravity from other extraterrestrial factors (radiation, vacuum). Combinations of simulated spaceflight conditions, including microgravity, will be necessary to check how this parameter affects the biomolecular level of lichens and their microbiome.

 

References

[1] Sancho, L.G., de la Torre, R., Horneck, G., Ascaso, C., de los Rios, A., Pintado, A., and Schuster, M. (2007) Lichens survive in space: results from the 2005 LICHENS experiment. Astrobiology 7:443–454. https://doi.org/10.1089/ast.2006.0046

[2] de la Torre, R., Sancho, L.G., Horneck, G., de los Ríos, A., Wierzchos, J., Olsson-Francis, K., and Ott, S. (2010) Survival of lichens and bacteria exposed to outer space conditions—results of the Lithopanspermia experiments. Icarus 208:735–748. https://doi.org/10.1016/j.icarus.2010.03.010

[3] Onofri, S., de la Torre, R., de Vera, J.P., Ott, S., Zucconi, L., Selbmann, L., Scalzi, G., Venkateswaran, K.J., Rabbow, E., Sánchez, F.J., and Horneck, G. (2012) Survival of rock-colonizing organisms after 1.5 year in outer space. Astrobiology 12: 508-516. https://doi.org/10.1089/ast.2011.0736

[4] de Vera, J.P., , and the BIOMEX-Team and associatesTeam (Ute Boettger, Rosa de la Torre Noetzel et al.) (2019) Limits of Life and the Habitability of Mars: The ESA Space Experiment BIOMEX on the ISS. Astrobiology, 19-2. https://doi.org/10.1089/ast.2018.1897.

How to cite: de la Torre Noetzel, R., Alvarez, O. B., Ortega-García, M. V., García Sancho, L., Villasante, A., del Olmo, J., de Vera, J. P., and Herranz, R.: Limits of life at spaceflight conditions: survival of lichens to simulated microgravity, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1055, https://doi.org/10.5194/epsc2022-1055, 2022.

16:40–16:50
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EPSC2022-1227
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ECP
Alvaro del Moral, Dominic Siggs, Mark G. Fox-Powell, Victoria K. Pearson, and Karen Olsson-Francis

Introduction

Icy moons of the giant planets contain liquid water oceans where habitability is feasible. A prime example is Jupiter’s moon, Europa, which could contain multiple regions where life might be sustained under its thick ice layer [1]. However, whether the physical and chemical conditions in Europa’s ocean are conducive to life is currently unknown. Terrestrial analogue environments provide one opportunity to study microbial dynamics under chemical conditions relevant to Europa. Knowledge of Europa’s ocean chemistry comes from models based on Earth-based observations and spacecraft flybys [2,3], which suggest that the ocean might be favourable to support life, specifically, chemolithotrophs that obtain energy by oxidising inorganic compounds [1,4]. Developments in machine learning (ML) algorithms offer the possibility of selecting terrestrial analogues with a high degree of similarity to the physicochemical environment proposed for Europa [5].

However, there are limitations to terrestrial analogues; conditions in these environments do not perfectly match the physicochemical conditions in Europa, especially when the moon’s ocean pressure ranges from a few hundred bar to over 1200 bar [1,2]. Thus, controlled lab experiments must also be used to fully simulate the desired extraterrestrial environment. The aim of this study was to integrate analogue and experimental approaches to cultivate a microbial community capable of growth under the specific physical and chemical conditions of Europa’s sub-surface ocean that can serve as a proxy to study the habitability of Europa.

Methods

The selection of a suitable analogue sample through ML[5] and the design of a growth media was based on a model for Europa’s ocean composition[6]. The environmental sample came from Basque Lake, Canada and the media was dominated by a carbonate-chloride rich chemistry at a salinity of 12.6 g/L and under 2 bar of 80%-20% H2/CO2 gas headspace [4,6]. Sub-culturing was performed to eliminate contaminants from the initial sample, with final cultures reaching cell densities of 105-107 cells per millilitre. This community was then transferred to a bespoke environmental simulation chamber (Figure 1) where it could be gradually conditioned to the physical conditions within Europa’s ocean. Specifically, the pressure was initially set at 20 bar (10-fold increase from the benchtop control) and then increased to 100, 200 and 300 bar to selectively cultivate communities adapted for growth under Europa ocean conditions. At the same time, samples were taken to monitor pressure-induced changes in the microbial community composition and their physiology. The chemical composition of the media was monitored using Ion Chromatography (IC) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The growth of the microbial community was monitored using fluorescence cell microscopy and its composition using 16s rRNA sequencing. Changes in microbial morphology due to pressure were investigated using Transmission Electron Microscopy (TEM).

 

Figure 1 Pressure vessel used as an environmental chamber where microbial communities can be exposed to different pressure and temperature regimes.

Results

Preliminary results demonstrate that microbial communities from Basque Lake can adapt to live under the conditions of Europa’s sub-surface ocean. There was an increased number of cells at 100 bar (6.35 x 106 cells ml-1 compared to 1.88 x 106 cells ml-1 at 2 bar) and growth was still measured at 300 bar (1.98 x 107 cells ml-1). However, pressure influenced the size of the cells, making them smaller and the generation of extracellular material (Figure 2) which will be further investigated using TEM. Future work will focus on isolating microorganisms from Europa’s simulated environment.

 

Figure 2 Fluorescence microscopy images of microbial communities growing in Europan chemical conditions under 2 bars of pressure (A) and 300 bars of pressure (B).

Conclusion

These high-pressure experiments have shown that microbes can adapt and grow under the conditions in the sub-surface ocean of Europa even after several sub-cultures. These microbial communities can now serve as a proxy to study life in this moon. This project could change how we approach the search for life in these moons and where we expect to find these organisms. The increased cell numbers under a pressure equivalent to the sub-surface environment of Europa point at a possible habitat where life might concentrate. Future work will investigate the effect on the morphology of the cells, as well as the formation of extracellular components, on the nucleation of ice at the sub-surface interface and thus how potential biosignatures might be captured into the ice shell and expressed to the surface.

References

1. Russell, M. J. et al. The possible emergence of life and differentiation of a shallow biosphere on irradiated icy worlds: The example of Europa. Astrobiology 17, 1265–1273 (2017).

2. Kivelson, M. G. et al. Galileo magnetometer measurements: A stronger case for a subsurface ocean at Europa. Science (1979) 289, 1340–1343 (2000).

3. Paganini, L. et al. A measurement of water vapour amid a largely quiescent environment on Europa. Nature Astronomy 4, 266–272 (2020).

4. Russell, M. J. et al. Serpentinization as a source of energy at the origin of life. Geobiology 8, 355–371 (2010).

5. del Moral, A. et al. Using supervised machine learning methods to improve the selection of analogue sites for studying habitability of the sub- surface ocean of Europa. 14, 10–12 (2022).

6. Melwani Daswani, M. et al. A Metamorphic Origin for Europa’s Ocean. Geophysical Research Letters 48, (2021).

How to cite: del Moral, A., Siggs, D., Fox-Powell, M. G., Pearson, V. K., and Olsson-Francis, K.: Exploring Europa’s biological potential using machine learning and laboratory simulations, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1227, https://doi.org/10.5194/epsc2022-1227, 2022.

16:50–17:00
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EPSC2022-918
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ECP
Miguel Ángel Fernández-Martínez, Brady O'Connor, Louis-Jacques Bourdages, Catherine Maggiori, and Lyle Whyte

Detecting unquestionable signatures of biological activity in extra-terrestrial Solar System bodies is one of the most challenging objectives in Astrobiology. Discerning if these signatures have been generated by extinct or actual extant organisms would also be of principal interest. While most of the latest exploration missions to Mars launched on 2020 (i.e. NASA’s Mars 2020) or being launched in the near future (ESA’s ExoMars) carry instruments - Raman spectrometers and MOMA (Mars Organic Molecule Analyser) - able to detect organic compounds, they lack the capabilities to undoubtedly confirm those signatures have been generated either by past or extant life.

Here we present the MICRO-life detection platform, a comprehensive, multi-technique instrumentation for molecular microbial ecology studies, intended to take part in future exploratory space missions. The MICRO-life detection platform already includes three complementary tools that, in the next future, would be operated at once without any human intervention. Thus, findings coming out from all the included techniques would be combined for a better assignment of putative positive results.

The first instrument included in the platform is MagLysis, a small, lightweight, solid-state, automatable instrument designed to help in the extraterrestrial detection of the most unambiguous and informative biosignatures: nucleic acids (NA). MagLysis aims to bead-beat the biomass in a sample to disrupt the cell walls and membranes, thus releasing the contents of the cell cytoplasm, including DNA and RNA molecules. The unique feature of MagLysis is that only ferromagnetic beads (made of stainless steel) are agitated inside the vessel by two opposing, low-inductance electromagnets, resulting in mechanical lysis (Fig. 1A). Reducing the mass actuated by the device to only the beads means that the power required is potentially low and that there are fewer moving parts, both extremely important features for space exploratory missions. Moreover, extracted DNA was successfully amplified by PCR and subsequently sequenced by the second instrument included in the platform, Oxford Nanopore Technologies’ (ONT) MinION.

ONT MinION is a fully portable device (Fig. 1B) able to carry out real-time analysis of DNA, RNA, proteins and other smaller molecules. This instrument has been tested in the International Space Station (ISS) and in field campaigns at our lab, with results that have been already published. With it, feasible sequence data can be obtained within 48 h from natural samples with only ~ 0.001 ng of DNA, as it has been already tested by us on terrestrial analogues of Mars and the Icy Moons, such as the High Arctic, Antarctica and Utah and Atacama Desert samples, as well as on samples that have been subjected to long periods of Mars-like conditions. Additionally, MinION results have been proved to reflect very similar microbial community compositions to those obtained by other techniques, such as Illumina MiSeq sequencing or LDChip.

Complementary to MinION, MICRO-life detection platform also includes a method for the detection and characterization of viable microorganisms based on their metabolic capacities: Microfluidic microbial activity microassay (μMAMA). μMAMA is a multi-well plate that focus on the capability of extant microorganisms - including yet unculturable species - to become metabolically active when they are supplied with different organic and inorganic substrates. The technique itself is based on redox-indicator dyes chemically associated to the substrates than can subsequently be measured by a spectrophotometer (Fig. 1C); additionally, it has been proved to work in a wide range of pH values or temperatures. This has been the case of samples from the High Arctic, where this technique has already shown that metabolically active communities were differentially found at 5 °C or 20 °C. Subsequently, those communities yielded positive results in a MinION sequencing process, showing that most of the members in the active communities belonged to Pseudomonas genus and demonstrating the complementarity of both techniques.

Attending to the results already obtained from cold extreme environments in polar regions and deserts (Mars and Icy Moons analogs), MICRO-life detection platform and self-developed techniques within are very promising tools for Astrobiological research. Their ease-of-use and the proof of being resistant to the most extreme conditions including space travel ones, make the platform a strong candidate to be employed in future extreme environment research and, in the mid-term, included in space exploratory missions as an important element to the search for extant extra-terrestrial life.

How to cite: Fernández-Martínez, M. Á., O'Connor, B., Bourdages, L.-J., Maggiori, C., and Whyte, L.: The comprehensive ‘MICRO-life detection platform’ applied to in situ research at Mars and Icy Moons terrestrial analogs, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-918, https://doi.org/10.5194/epsc2022-918, 2022.

Coffee break
Chairpersons: Hector-Andreas Stavrakakis, Frédéric Foucher
17:30–17:40
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EPSC2022-15
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ECP
Laura Clodoré, Frédéric Foucher, Keyron Hickman-Lewis, Stéphanie Sorieul, Matthieu Réfrégiers, Guillaume Collet, and Frances Westall
Introduction:

Did life ever exist on Mars? This is the question that present and future missions to Mars (MSL, Mars 2020, MSR, and ExoMars) are trying to answer.

Although the present conditions on Mars make the presence of extant life highly unlikely at the surface, life may have appeared early in its history, during the Pre-Noachian and Noachian periods, when surface conditions permitted habitability and, potentially, the development of the first forms of cellular life (Cockell et al., 2014; Westall et al., 2015). However, given the conditions of punctuated habitability, if life ever appeared, it most likely remained at a relatively primitive stage of evolution (chemotroph-like organisms, although anoxygenic photosynthetisers cannot be completely ruled out) and the associated remains would be comparable to the very small and subtle chemotrophic microfossils observed in the early terrestrial record (Westall et al., 2015). In order to improve their detection in martian rocks, we therefore study fossil traces of life associated with ancient, 3.45 Ga, terrestrial volcanic sediments whose biological signatures are possible analogues of the signatures of life that could be found on Mars.

The 3.446 Kitty’s Gap chert:

The 3.45 Ga Kitty’s Gap chert (Pilbara, Australia) is a typical example of silicified volcanic sediments deposited in a shallow, littoral water environment, and in the vicinity of a hydrothermal vent linked to a volcanic system, an excellent analogue for the Noachian environments on Mars (Fig. 1A; Westall et al., 2006, 2011).

The Kitty’s Gap sediments hosted microorganisms interpreted as anaerobic, autotrophic chemolithotrophs that colonized the surface of volcanic particles, as well as the dusty matrix (Fig. 1B-C). These kinds of microbes were common on the early Earth, living in anaerobic, volcanic environmental conditions similar to those on early Mars (Westall et al., 2015). The microorganisms occur as silicified, small (< 1 µm) coccoidal structures forming very small and dispersed colonies (Fig. 1D). Moreover, the total sediment is low in organic carbon (0.01–0.05 wt. %). Therefore, the carbonaceous remains of these microorganisms are very subtle and difficult to identify, and their analyses required a multi-technique approach to demonstrate their biogenicity.

Fig. 1. (A) Outcrop of the volcanic sediments in the Kitty’s Gap chert. Scale-lens cap 5.4 cm. (B) Optical image of the volcanic particles in the rock. (C) Volcanic particle (outlined in B) surrounded by organic matter (brown). (D) SEM micrograph showing colonies of chemolithotrophs in volcanic sediments (Westall et al., 2006).

Microfossils study:

The identification of fossil microorganisms is based on a number of criteria (see Westall et al., 2006) including:

- compatibility of the depositional environments with the existence of living organisms, such as physico-chemical conditions, availability of energy, carbon and nutrients sources;

- demonstration of characteristics indicative of biogenicity, i.e. morphological and biogeochemical characteristics;

- interactions between living organisms and their immediate environment, such as microbial alteration and colonization of the substratum, formation of mats/biofilms, stabilization of the sediments via fossilization processes;

- lack of abiogenic alternatives.

In addition to proving biogenicity, it is also necessary to prove syngenicity.

Multi-technique study to evaluate environmental conditions…

The habitability of the Kitty’s Gap chert is investigated by multiple complementary instruments in order to characterize the paleoenvironment conditions of the rocks. Macroscopic and microscopic observations (optical microscopy and SEM), Raman spectroscopy, ICP-MS and LA-ICP-MS provide information about the origin and formation of rocks, but also on the alteration processes that contributed to their mineralogical, morphological and chemical transformation, as well as their preservation (Fig. 2).

Fig. 2. MuQ-normalised bulk ICP-MS measurements of REE + Y in the two studied units, 00AU39 and 00AU40. The REE + Y profiles indicate a deposit in a semi-enclosed basin, influenced by seawater, terrigenous, and hydrothermal inputs.

…and determine biogenicity

The characterization of primitive fossils microbes requires the identification of morphological, elemental and molecular biosignatures. For this purpose, the carbonaceous matter around the volcanic particles (Fig. 1C) is studied using different observation and analytical techniques such as optical and electronic microscopy, Raman spectroscopy, UV and visible fluorescence spectroscopies, EDX, ToF-SIMS, and FTIR. Trace metal elements associated with metabolisms as well as trapped by the extracellular polymeric substances (EPS) prior to silicification may be also identified using techniques such as Particle-Induced X-ray Emission, X-ray micro-fluorescence, and LA-ICP-MS (Fig. 3).

Fig. 3. µ-PIXE elemental mapping of a volcanic particle in the Kitty’s Gap chert. The volcanic particle is surrounded by organic matter enriched in transition metal elements, including some biofunctional elements, such as Ti, Cr, Fe, Co, Ni and Cu.

Conclusion: Formed in situ in coastal volcanic sediments, the organic coatings on volcanic detrital grains and small colonies of interpreted coccoidal chemolithotrophic organisms in the Kitty’s Gap chert are representative of possible martian biosignatures, especially some of which could be decisive for the detection of potential traces of life on Mars.

Summary: Investigation of the habitability of the paleoenvironment of the oldest cellular forms of life found on Earth, and documentation of primitive life signatures and the methods used to characterize them, will be relevant for selecting samples in situ for analyses and/or sample return from Mars, as well for identifying biological signatures in returned martian materials.

References:

Cockell, C.S. (2014) Trajectories of martian habitability. Astrobiology 14:182–203.

Westall, F. et al. (2006) The 3.466 Ga “Kitty’s Gap Chert”, an early Archean microbial ecosystem. Geological Society of America 405:105–131.

Westall, F. et al. (2011) Volcaniclastic habitats for early life on Earth and Mars: A case study from ~3.5 Ga-old rocks from the Pilbara, Australia. Planetary and Space Science 59:1093–1106.

Westall, F. et al. (2015) Biosignatures on Mars: What, Where, and How? Implications for the Search for Martian Life. Astrobiology 15:998–1029.

 

How to cite: Clodoré, L., Foucher, F., Hickman-Lewis, K., Sorieul, S., Réfrégiers, M., Collet, G., and Westall, F.: Identifying biosignatures in a Mars-analogue volcanic rock: The ~3.5 Ga Kitty’s Gap chert, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-15, https://doi.org/10.5194/epsc2022-15, 2022.

17:40–17:50
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EPSC2022-189
|
ECP
|
MI
|
Christian Lorenz, Elisabetta Bianchi, Giovanni Poggiali, Giulia Alemanno, Renato Benesperi, John Robert Brucato, Stephen Garland, Jörn Helbert, Andreas Lorek, Alessandro Maturilli, Alessio Papini, Jean-Pierre de Vera, and Mickael Baqué

Introduction

One of the main topics of astrobiology research is the study of life’s limits in stressful environments. The study of organisms in extreme environments might give an indication about their potential adaptive plasticity, in the view of a climate change perspective, the terrestrial geological past and future scenarios, as well as extra-terrestrial habitats such as Mars’ surface. Lichens - with their excellent adaptive abilities - represents an extremely interesting case study. Several astrobiological studies involving lichens - that are symbiotic association between a fungus and an alga and/or acyanobacterium - proved the ability of these organisms to resist and thrive in extreme environments such as space and Mars’ surface simulated conditions [1, 2]. We have already tested the lichen species Xanthoria parietina (L.) Th. Fr. in simulated space conditions, that was able to survive and to reactivate after exposure [3]. X. parietina is a cosmopolitan foliose lichen that grows on barks and rocks [4]. This species shows high tolerance to air pollutants, heavy metals, and resistance to UV-radiation thanks to the shielding properties of the secondary metabolite parietin [5, 6]. Here we present a new study on the survival of X. parietina under simulated Mars conditions performed at the Mars Simulation Facility of the DLR Institute of Planetary Research in Berlin (Fig.1).

Figure 1 - Mars Simulation Facility at DLR with the opened experiment chamber.

Methods

The aim of the study was to assess the survivability of Xanthoria parietina under simulated Mars conditions for 30 days [7, 8]. Inside the Mars simulation chamber, eight samples (Fig.2) were exposed to the simulated atmospheric conditions of Mars of which four were fully UV-irradiated with day-night cycles (FM, Full-Mars) and the other four kept in darkness (DM, Dark-Mars). A three-gas mixture of 95% CO2, 4% N2 and 1% O2 was used as best approximation of Mars-like atmospheric conditions, with a constant pressure of 600Pa. Temperature and humidity were subjected to day-night cycles, reaching during daytime 15°C and 0% RH, and during night -55°C and 100% RH (Fig.3) according to Martian thermophysical conditions at mid-latitudes. UV-radiation for FM samples was simulated using a Xenon UV-lamp (spectral range 200 nm – 2200 nm) that was automatically turned on for 16 h (day) and turned off for 8 h (night) daily. The total average radiation dose for FM was 2452.32 J/cm2 and the average instantaneous irradiance on the sample spots was 14,2 W/m2 [9]. Four other samples (Fig.2) were kept in control conditions during the experiment, at the constant temperature of 25°C, daily wetted and 12h dark and 12h light (ca. 50 μmol m-2 s-1 PAR photons). Several analyses were carried out to study all the samples before, during and after the exposure to the extreme Mars conditions. In detail, this experiment was performed aiming:

  • to monitor the lichen vitality through chlorophyll a fluorescence (FV/FM) as photosynthetic efficiency parameter, carrying out in situ and after treatment analyses,
  • to evaluate the oxidative stress due to the extreme conditions, highlighting eventual changes in the lichen carotenoids’ Raman signatures,
  • to verify eventual modifications in the infrared features (peak shifting) in the lichen FTIR reflectance spectrum possibly related to UV-photodegradation effects,
  • to highlight possible variations in the lichen ultrastructure through TEM analysis.

Figure 2 - Xanthoria parietina samples ready for the experiment. First row (from above): full Mars samples, second row: dark Mars samples, third row: control samples.

Figure 3 - Detail of the day-night cycles of the simulated Mars conditions (temperature, red thick line; humidity, blue thin line) and fluorescence variation values for both the treatments (FM and DM).

Results

The results showed significant differences between FM and DM photosynthetic efficiency parameter during exposure to Mars environment, exhibiting FV/FM values correlated with temperature and humidity day-night cycles (Fig.3). The FV/FM recovery values showed significant differences between the treatments too, highlighting that FM conditions caused stronger effects on fluorescence values. Additional analyses show possible changes in the Raman and FTIR spectra of the irradiated samples with several features involved. Overall, Xanthoria parietina was able to survive to FM conditions, and for this reason it may be considered a candidate for long exposure in space and evaluations on the photodegradability of parietin in extreme conditions.

 

Reference

[1] Onofri, S., de la Torre, R., de Vera, J. P., Ott, S., Zucconi, L., Selbmann, L., Scalzi, G., Venkateswaran, K. J., Rabbow, E., Sánchez Iñigo, F. J., and Horneck, G. (2012). Survival of rock-colonizing organisms after 1.5 years in outer space. Astrobiology12(5), 508-516.

[2] De Vera, J. P., Möhlmann, D., Butina, F., Lorek, A., Wernecke, R., and Ott, S. (2010). Survival potential and photosynthetic activity of lichens under Mars-like conditions: a laboratory study. Astrobiology10(2), 215-227.

[3] Lorenz, C., Bianchi, E., Benesperi, R., Loppi, S., Papini, A., Poggiali, G., & Brucato, J. R. (2022). Survival of Xanthoria parietina in simulated space conditions: vitality assessment and spectroscopic analysis. International Journal of Astrobiology, 1-17.

[4] Nimis P.L., 2016. ITALIC - The Information System on Italian Lichens. Version 5.0. University of Trieste, Dept. of Biology, (http://dryades.units.it/italic), accessed on 2022, 05, 09. for all data contained in the taxon pages, including notes, descriptions, and ecological indicator values. 

[5] Silberstein, L., Siegel, B., Siegel, S., Mukhtar, A., and Galun, M. (1996). Comparative Studies on Xanthoria parietina, a Pollution Resistant Lichen, and Ramalina duriaei, a Sensitive Species. I. Effects of Air Pollution on Physiological Processes. The Lichenologist, 28:355-365.

[6] Solhaug, K. A., and Gauslaa, Y. (1996). Parietin, a photoprotective secondary product of the lichen Xanthoria parietinaOecologia, 108:412-418.

[7] Lorek, A., and Koncz, A. (2013). Simulation and measurement of extraterrestrial conditions for experiments on habitability with respect to Mars. In Habitability of Other Planets and Satellites (pp. 145-162). Springer, Dordrecht.

[8] De Vera, J. P., Schulze-Makuch, D., Khan, A., Lorek, A., Koncz, A., Möhlmann, D., and Spohn, T. (2014). Adaptation of an Antarctic lichen to Martian niche conditions can occur within 34 days. Planetary and Space Science98, 182-190.

[9] Cockell, C. S., Catling, D. C., Davis, W. L., Snook, K., Kepner, R. L., Lee, P., and McKay, C. P. (2000). The ultraviolet environment of Mars: biological implications past, present, and future. Icarus146(2), 343-359.

How to cite: Lorenz, C., Bianchi, E., Poggiali, G., Alemanno, G., Benesperi, R., Brucato, J. R., Garland, S., Helbert, J., Lorek, A., Maturilli, A., Papini, A., de Vera, J.-P., and Baqué, M.: Survivability of Xanthoria parietina in simulated Mars conditions for 30 days, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-189, https://doi.org/10.5194/epsc2022-189, 2022.

17:50–18:00
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EPSC2022-275
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ECP
Jacob Heinz, Joerg Doellinger, Deborah Maus, Andy Schneider, Peter Lasch, Hans-Peter Grossart, and Dirk Schulze-Makuch

Introduction: While perchlorate (ClO4-) salts occur only occasionally in natural environments on Earth, they seem to be widely distributed on Mars [1]. The hygroscopicity of these salts and their potential to reduce the freezing point of pure water might enable the provision of liquid water by the formation of temporarily stable liquid brines close to the surface of Mars [2]. However, low water activities and the enhanced chaotropicity (i.e. the potential of biomacromolecule destabilization) of perchlorate pose a huge challenge for putative microorganisms in these brines [3]. Here we present the results of the first study investigating perchlorate-specific stress responses (i.e., with a significant distinction compared to general salt stress) of a halotolerant model organism, Debaryomyces hansenii, with an untargeted proteomic approach to provide fundamental understanding of the required cellular adaptation mechanisms for life in perchlorate-rich habitats on Mars.

Methodology: Growth experiments with D. hansenii were conducted in liquid growth media DMSZ #90 containing either NaCl, NaClO4 or no additional salt. Water activities (aw) of the growth media were measured with the Rotronics® ‘HC2-AW-USB’ aw meter. Proteomics analyses of the grown cultures were conducted using the SPEED (Sample Preparation by Easy Extraction and Digestion) protocol described previously [4].

Results: While D. hansenii grew at NaCl concentrations of up to 4.0 mol/kg (aw = 0.854), growth in perchlorate-containing media was obtained only at NaClO4 concentrations up to 2.5 mol/kg (aw = 0.926) [5]. The proteomics data [6] indicated that the chaotropicity of perchlorate is likely to be the major factor of the reduced tolerance of D. hansenii towards NaClO4 compared to NaCl, while the perchlorate´s oxidative properties seem to play only a subordinated role in growth limitation. This is consistent with previous studies finding a high kinetic barrier for the reduction reaction of the perchlorate anion in solution [7].

The chaotropic activity of perchlorate leads to a destabilization of biomacromolecules such as proteins. Consequently, cells of D. hansenii showed upregulation of metabolic pathways involved in glycan biosynthesis, protein glycosylation and the requisite protein transport mechanisms when exposed to perchlorate stress, presumably in order to increase protein stability. Furthermore, the biosynthesis and reorganization of cell wall components, e.g. chitin, was significantly upregulated compared to NaCl-induced stress, indicating the necessity of stabilizing the cell envelope. In addition to these perchlorate-specific stress responses, many other metabolic pathways were expressed similarly in NaCl and NaClO4-stressed cells, such as signaling pathways, elevated energy metabolism, or osmolyte biosynthesis.

Conclusions: To counteract perchlorate-induced chaotropic stresses, cells initiate metabolic pathways that stabilize biomacromolecules and cell envelopes. We hypothesize that these stress responses would also be relevant for putative Martian microorganisms, which likely developed chaotropic defense strategies in order to counteract the relatively high perchlorate concentrations in the Martian regolith. Chaotropic-specific adaptations might be the evolutionary development of stabilized confirmations of biomacromolecules in which structures with covalent bounds and cross-linking are favored over looser electrostatic interactions, hydrogen bonding or hydrophobic effects. Additionally, cell components susceptible to chaotropic stress might be stabilized by the attachment of polymers similar to stabilization effects via protein glycosylation as observed in our experiments. Characteristic biomarkers might result from these adaptions which will likely prompt further investigations.

References:

[1] Clark, B.C. and Kounaves, S.P. (2016) IJA, 15, 311–318; doi: 10.1017/S1473550415000385.

[2] Martín-Torres, F.J., et al. (2015) Nat. Geosci. 8, 357–361; doi: 10.1038/ngeo2412.

[3] Hallsworth, et al. (2007) Environ. Microbiol., 9, 801–813; doi: 10.1111/j.1462-2920.2006.01212.x.

[4] Doellinger, J., et al. (2020) MCP, 19, 209–222; doi: 10.1074/mcp.TIR119.001616.

[5] Heinz, J., et al. (2021) Life, 11; doi: 10.3390/life11111194.

[6] Heinz, J., et al. (2022) preprint at biorxiv.org; doi: 10.1101/2022.05.02.490276.

[7] Urbansky, E.T. (1998) Bioremediat. J., 2, 81–95; doi: 10.1080/10889869891214231.

 

How to cite: Heinz, J., Doellinger, J., Maus, D., Schneider, A., Lasch, P., Grossart, H.-P., and Schulze-Makuch, D.: Perchlorate-induced proteomic stress responses of Debaryomyces hansenii and their consequences for the habitability of Martian brines, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-275, https://doi.org/10.5194/epsc2022-275, 2022.

18:00–18:10
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EPSC2022-584
John Robert Brucato, Cristina Garcia Florentino, Andrew Alberini, Teresa Fornaro, Juan Manuel Madariaga, and Giovanni Poggiali

Laboratory simulations of the Martian conditions are essential in order to interpret results collected on Mars exploration missions. Among them, the study of the degradation and/or the evolution of possible organic biomarkers adsorbed on minerals is very important. The thin atmosphere of Mars allows ionizing radiations to reach the surface of the planet and drive the photochemical production of strong oxidants in the soil which possibly degrade the organics on the Mars´ surface1. However, traces of ancient life forms may be found in old mineral deposits preserved within protected environments recently accessible due to erosion or impacts.It is known that mid-UV radiation is among the main degradation agents on Mars2. Thus, inspection the stability and reactivity of possible biomarkers in the eolian-mobile layer and in the different fresh subsurface minerals exposed at the surface of Mars is important. Laboratory simulations of the harsh Martian conditions can evaluate the likelihood of preservation of potential biomarkers on different minerals on Mars. This provides a critical support to rover missions on Mars, helping to select the most appropriate minerals to find organic molecules and therefore, possible biomarkers.

 

In this work, the interaction and stability of L-histidine in saponite are studied. The saponite mineral was chosen because is a common product of low-temperature reaction between water and the mafic minerals on Mars. In addition, saponite in old cold basaltic crust is favourable for microbial life.3 L-histidine, an α- amino acid used in the biosynthesis of proteins, was chosen as biomarker because it is very diagnostic of life. Moreover, it presents different protonation states depending on the pH, which might result in different interaction with the mineral at different pHs.

 

The samples were prepared using the equilibrium adsorption method. In particular, pure synthetic saponite was put in contact with different solutions of L-histidine at pH 2.7 and 9.6, in order to investigate the effect of acidic or alkaline conditions on the adsorption process. The suspensions were kept for 24 hours on rotation to reach the equilibrium state during molecular adsorption, and then they were dried in an oven at 40C.

 

The samples were analyzed by X-Ray Diffraction to understand if any intercalation of L-histidine in the negatively-charged interlayer sites of saponite occurs at acidic pH. Further characterization of molecule-mineral interactions was carried out by Transmittance and Diffuse Reflectance InfraRed Fourier Transform Spectroscopy. Finally, the samples were processed under Martian-like UV irradiation conditions using an experimental setup which allows to monitor the degradation kinetics in situ by infrared spectroscopy analysis during UV irradiation. These experiments allowed us to investigate the catalytic/protective behaviour of saponite towards L-hystidine in different pH conditions, and obtain the degradation cross section of L-histidine adsorbed on saponite compared to the pure molecule, along with the half-lifetime of degradation under Martian UV flux.

 

References

 1Quinn, R. C.; Martucci, H. F. H.; Miller, S. R.; Bryson, C. E. Perchlorate Radiolysis on Mars and the Origin of Martian Soil Reactivity. Astrobiology 2013, 13 (6), 515–520.

2Fornaro, T.; Steele, A.; Brucato, J. R. Catalytic/Protective Properties of Martian Minerals and Implications for Possible Origin of Life on Mars. Life 2018, 8.

3Y. Sueoka, S. Yamashita, M. Kouduka, Y. Suzuki, Deep Microbial Colonization in Saponite-Bearing Fractures in Aged Basaltic Crust: Implications for Subsurface Life on Mars, Frontiers in Microbiology. 10 (2019).

How to cite: Brucato, J. R., Garcia Florentino, C., Alberini, A., Fornaro, T., Madariaga, J. M., and Poggiali, G.: L-histidine in Saponite: Detection, Characterization and UV Degradation Studies for Biosignature Identification on Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-584, https://doi.org/10.5194/epsc2022-584, 2022.

18:10–18:20
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EPSC2022-590
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ECP
|
Ophélie Mcintosh, Cyril Szopa, Caroline Freissinet, Arnaud Buch, and David Boulesteix

Introduction. The harsh oxidative and radiative conditions of the Martian environment influence the fate of organic molecules present on its surface. Formation of radical species was suggested to transform organic macromolecules into carboxylic acid through Fenton chemistry (1, 2) or irradiation semiconductor surfaces (3). Aromatic carboxylic acids such as phthalic acid or benzoic acid are thought to be abundant on the Martian surface as they are in stable intermediate oxidation states and can be formed from the oxidation of Polycyclic Aromatic Hydrocarbons (PAHs) (1, 4) or alkylbenzene compounds (4) coming from endogenous or exogenous sources. Because benzene carboxylates are metastable, they should not be entirely oxidized into volatile molecules such as CO2 or O2, but instead, ionized by solar radiation to form organic salts (2, 4, 5). Benner et al. (2000) suggested that the low volatility of these salts could compromise their in situ detection through thermal extraction analyses as performed by analytic chemistry laboratories onboard Martian surface probes, such as the Sample Analyzer at Mars (SAM) experiment onboard Curiosity rover or the Mars Organic Molecular Analyzer (MOMA) instrument of the Rosalind Franklin Exomars rover (4-6). To determine the possibility to identify these molecules through direct or indirect detection on Mars, we examined laboratory results from SAM and MOMA-like Gas Chromatography-Mass Spectrometry (GC-MS) analyses of two acid/salt couples (phthalic acid/calcium phthalate and benzoic acid/calcium benzoate). We analyzed the difference in behavior and signatures of both molecular forms when using pyrolysis and wet chemistry experiments used in SAM and MOMA, and the relevance of these results in the search of organic molecules on Mars.

Method. Synthetic samples were made by mixing the carboxylic acid molecules or their organic salts standards at 1wt.% in fused silica, to simulate a relatively inert mineral matrix. The samples were pyrolyzed in SAM-like conditions with a ramp of 35°C.min-1 and in MOMA-like conditions in flash pyrolysis at 500°C and 800°C.  The volatiles released from each sample were analyzed by Evolved Gas Analysis (EGA) and Gas Chromatography-Mass Spectrometry (GC-MS). We also performed derivatization experiments to help detect refractory organic compounds, with N,N-methyl-tert-butyl-dimethylsilyltrifluoroacetamide (MTBSTFA), used for wet chemistry experiments in SAM, and N,N-Dimethylformamide dimethyl acetal (DMF-DMA), to be used in the MOMA experiment of the ExoMars mission.

Organic acid/salt behavior under pyrolysis conditions. As predicted by Benner et al. (4), when analyzed through pyrolysis-GC-MS, the organic salts species did not produce the organic parent molecule (phthalic acid or benzoic acid (Fig. 1 (a)). However, we have identified two by-products characteristic of the degradation of the organic salts, diphenylmethane (Fig. 1 (b)) and triphenylmethane (Fig.1 (b)) which were absent of the chromatograms of the acid species. These results show that for both carboxylic acid couples studied, the acid and the salt don’t follow the same degradation pathway resulting in differences in the species detected as well as major differences in the abundance of products observed in the chromatograms. This means that if carboxylic acids are present on Mars in their saline form linked to calcium cations, we would not be able to identify it through the detection of its acid form with the SAM nor MOMA pyrolysis set-ups, but rather through the detection of characteristic by-products that would serve as indirect clues for identification.

Figure 1. Chromatograms obtained under the same analytical conditions as the pyrolysis in SAM. (a) benzoic acid mixed at 1 wt. % in fused silica and (b) calcium benzoate mixed at 1 wt. % in fused silica.

Organic acid/salt derivatized with MTBSTFA and DMFDMA.

 

Figure 2. Bar chart representing the abundance of derivatized benzoic acid obtained with calcium benzoate and benzoic acid. The derivatization reagent used was DMFDMA (a) and MTBSTFA (b).

When derivatized with DMFDMA or MTBSTFA, both the acid and the organic salt produced the derivatized product of the carboxylic acid. Both the phthalic acid and benzoic acids have a higher derivatization yield than their salt counterpart with both derivatization reagents. This is likely due to a better availability of the hydrogen on the carboxylic acid function. Moreover, we obtained a higher yield of both the acid and the salt with MTBSTFA than with DMF-DMA, with the loss of detection of calcium phthalate derivative with the latter. In conclusion, if present in the Martian soil, aromatic organic salts could be directly detected through wet chemistry experiments, showing the complementarity of this technique with pyrolysis.

References. (1) Oró et al. (1979) Life Sciences and Space Research, 77-86. (2) Donald et al. (2013) Science. (3) Fox et al. (2019) Journal of Geophysical Research: Planets 124, 3257-3266. (4) Benner et al. (2000) Proceedings of the National Academy of Sciences 97, 2425-2430. (5) Lasne et al. (2016) Astrobiology 16, 977-996. (6) Hakkinen et al. (2014) Environ Sci Technol 48, 13718-13726.

How to cite: Mcintosh, O., Szopa, C., Freissinet, C., Buch, A., and Boulesteix, D.: Analysis of aromatic organic salts with gas chromatography-mass spectrometry and implications for their detection at Mars surface with in situ experiments , Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-590, https://doi.org/10.5194/epsc2022-590, 2022.

18:20–18:30
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EPSC2022-1158
|
ECP
Looking for biosignatures in a pristine Mars analogue environment on Earth
(withdrawn)
Vera Palma, Nicasio T. Jiménez-Morillo, Francesco Sauro, Matteo Massironi, José M. De la Rosa, José A. González-Pérez, Bodgan P. Onac, Igor Tiago, Ana Teresa Caldeira, and Ana Z. Miller
Display time: Wed, 21 Sep 14:00–Fri, 23 Sep 16:00

Posters: Thu, 22 Sep, 18:45–20:15 | Poster area Level 2

Chairpersons: Alex Price, Mickael Baqué
L2.69
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EPSC2022-465
|
ECP
Denise Kölbl, Elke Rabbow, Petra Rettberg, Kristina Beblo-Vranesevic, André Parpart, Hajime Mita, Akihiko Yamagishi, and Tetyana Milojevic

With future long-term space exploration and life detection missions on Mars, understanding the microbial survival beyond Earth as well as the identification of past life traces on other planetary bodies becomes increasingly important. The series of the Tanpopo space mission experiments target a long-term exposure (one to three years) of microorganisms on the KIBO Module of the International Space Station (ISS) in the low Earth orbit (LEO) (Kawaguchi et al., 2020; Ott et al., 2020). In the search for possible past and/or present microbial life on Mars, metallophilic archaeal species are of a special interest due to their inherent extraordinary characteristics. Chemolithotrophic archaea (e.g., from the order Sulfolobales) employ a number of ancient metabolic pathways to extract energy from diverse inorganic electron donors and acceptors. Metallosphaera sedula, an iron- and sulfur-oxidizing chemolithotrophic archaeon, which flourishes under hot and acidic conditions (optimal growth at 74°C and pH 2.0), was cultivated on genuine extraterrestrial minerals (Milojevic et al., 2019; Milojevic et al., 2021) as well as synthetic Martian materials (Kölbl et al., 2017). In all cases, M. sedula cells were able to utilize given mineral materials as the sole energy source for cellular growth and proliferation. During the growth of M. sedula cells on these materials, a natural mineral impregnation and encrustation of microbial cells was achieved, followed by their preservation under the conditions of desiccation (Kölbl et al. 2020). Our studies indicate that this archaeon, when impregnated and encrusted with minerals, withstand long-term desiccation and can be even recovered from the dried samples to the liquid cultures (Kölbl et al., 2020). The achieved preservation of desiccated M. sedula cells facilitated our further survivability studies with this desiccated microorganism under simulated Mars-like environmental conditions and during the Tanpopo-4 space exposure experiment.

Consequently, M. sedula cells grown on various mineral materials were exposed at the Astrobiology Space Simulation facilities (DLR, Cologne) to a simulated Martian environment for one month, to ensure their suitability for a long-term experiment on the ISS within the Tanpopo-4 mission. Recovery of cells after exposure to a simulated Martian environment shows an insignificant impairment in cellular growth compared to ground control cells.

A set of desiccated M. sedula cells grown on Martian breccia NWA 7034 (Milojevic et al., 2021) has already been launched for 1 year outside the ISS to Mars-like conditions in frames of the Tanpopo-4 mission (2022-2023). Upon retrieval of cells from the ISS, we will evaluate survivability of this chemolithoautotroph protected by various mineral materials in Mars-like environment. Furthermore, high-resolution electron microscopy and (nano)-spectroscopy techniques will be applied to identify preservable biosignatures of chemolithotrophic life on Martian materials.

Resolving the interface of microbial interactions with Mars minerals under the influence of destructive Martian environmental constrains can bring us closer to identify traces of unicellular life for current and future Mars exploration missions. We will also reveal a role of mineral encapsulation as a natural shielding crust for cell protection during exposure to simulated Martian conditions.

References:

Kawaguchi Y. et al., Front. Microbiol. 11:2050. (2020) doi: 10.3389/fmicb.2020.02050

Kölbl D. et al., Front. Microbiol. 8, 1918 (2017) doi: 10.3389/fmicb.2017.01918

Kölbl D. et al., Front. Astron. Space Sci.  7:41 (2020) doi: 10.3389/fspas.2020.00041

Milojevic T. et al., Sci. Rep. 9, 18028 (2019). doi: 10.1038/s41598-019-54482-7

Milojevic T. et al., Commun. Earth Environ. 2, 39 (2021) doi: 10.1038/s43247-021-00105-x

Ott E. et al., Microbiome 8, 150 (2020) doi: 10.1186/s40168-020-00927-5

 

How to cite: Kölbl, D., Rabbow, E., Rettberg, P., Beblo-Vranesevic, K., Parpart, A., Mita, H., Yamagishi, A., and Milojevic, T.: Metallosphaera sedula on a Mission – mimicking Mars in frames of the Tanpopo 4 mission, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-465, https://doi.org/10.5194/epsc2022-465, 2022.

L2.70
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EPSC2022-537
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ECP
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Beatriz Gallego Fernandez, Claudia Mosca, Claudia Fagliarone, and Daniela Billi

Martian regolithic soil is considered an inhospitable environment to life as we know it with low availability of nutrients and the presence of powerful oxidants, namely perchlorate salts. Extreme microorganisms such as cyanobacteria of the genus Chroococcidiopsis dominate rock-dwelling communities in extreme deserts resembling the actual Martian environment. The strain Chroococcidiopsis 029, extremely tolerant to desiccation, ionizing, and UV radiation, can thrive in Mars-like conditions in a dried state. In the present work, we investigated the response of Chroococcidiopsis 029 when grown for a 3-week period using Martian regolith simulant containing 2.4 mM perchlorate anions. The growth either in the planktonic cells or biofilm life style was monitored following the in chlorophyll a content. The cellular and molecular responses to 2.4 mM perchlorate anions was studied following cell viability according to: i) PCR-PMA assay, ii) changes in gene expression of three SOD-coding genes (soda 2.1, soda.2, and sodC), and iii) production of intracellular ROS as revealed by CLSM. Results suggested that perchlorate did not compromise cell viability and that a significant over-expression of three SOD isoforms occurred after the one-week exposure with a greater expression of the membrane-bound MnSOD (sodA 2.1) in comparison to the cytoplasmic isoforms MnSOD (sodA 2.2) and Cu/ZnSOD (sodC). The accumulation of ROS within the cells was observed after 1-day exposure to perchlorate. Future investigations on the effect of Mars-like conditions in hydrated biofilms with 2.4 mM ClO4- and Martian regolith simulant will be carried out supported by the Europlanet scholarship 2024. These results are relevant for the habitability of Mars and the development of In-situ Resource Utilization.

How to cite: Gallego Fernandez, B., Mosca, C., Fagliarone, C., and Billi, D.: Responses of a desert cyanobacterium to prolonged exposure to perchlorate: implications for the habitability of Mars and In-Situ Resource Utilization, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-537, https://doi.org/10.5194/epsc2022-537, 2022.

L2.71
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EPSC2022-550
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ECP
Anne Gries, Jacob Heinz, and Dirk Schulze-Makuch

Introduction

All known terrestrial life forms require liquid water to survive and grow. Therefore, under the conditions present on Mars today, sub-zero brines might be one of few environments allowing for microbial life to persist. These brines likely contain perchlorates which have been found in martian regolith (Hecht et al. 2009). Whilst their hygroscopicity as well as their potential to lower the freezing point of water support the presence of liquid water, ion-specific toxic characteristics such as chaotropicity may be detrimental for many organisms.

An organism thriving under very high salt concentrations is the halophilic archaeon Haloferax volcanii isolated from the Dead Sea (Mullakhanbhai and Larsen, 1975). Whilst halophilic archaea require salt, most importantly sodium chloride (NaCl), to survive, they only tolerate limited amounts of sodium perchlorate (Oren et al. 2014).

Here we present the concept and preliminary results of experiments investigating the stress responses of H. volcanii growing in medium containing sodium perchlorate (NaClO4). To determine stress caused specifically by NaClO4, and not by general ionic or oxidative stress or low water activity, results are compared to stress responses caused by NaCl and glycerol.

Methods

H. volcanii was grown at 40°C in altered DSMZ medium #97, where MgSO4 was replaced by MgCl2 and the concentration of NaCl was lowered from 4 to 1.7 mol/kg, in order to allow the addition of different amounts of NaClO4, glycerol, or additional NaCl (up to NaCl saturation). Growth was tracked by measuring the optical density at 600 nm and regularly verified by colony forming unit (CFU) counts. Morphology was observed by light microscopy. Additional methods such as proteomics will be applied in upcoming experiments for analysing the stress responses in cells grown under the highest possible stress conditions.

Preliminary Results

H. volcanii is able to grow in medium containing 1.7 mol/kg of NaCl up to saturating concentrations, as was expected based on the very high tolerated NaCl range already described by Mullakhanbhai and Larsen (1975). Although visibly reduced, growth occured also in medium containing up to at least 0.6 mol/kg NaClO4, which was achieved by letting the cells adapt to incrementally increasing NaClO4 concentrations.

Fully substituting NaCl by NaClO4 did not support any growth and resulted in complete death of the cell culture, as suggested by lack of CFUs. Hence, it is likely that the ClO4- anion cannot provide the necessary conditions for cell metabolism accomplished by Cl- and possibly exhibits additional stress factors like chaotropic destabilization of biomacromolecules, as observed recently in the halotolerant yeast Debaryomces hansenii (Heinz et al. 2022). Although the NaCl tolerance of H. volcanii is higher, the tolerance for NaClO4 is much lower than that of D. hansenii. Unlike the yeast, H. volcanii has no cell wall and, as a prokaryote, no cell compartmentalisation in general, which might cause increased susceptibility towards the destabilizing properties of perchlorate. Various cell morphologies, ranging from coccoid to rod shaped as well as varied sizes were observed under the different stress conditions, calling for additional research.

Outlook

Further experimentation is needed to confirm the abovementioned results and to determine the maximum solute concentrations at which H. volcanii can grow. Stress responses of cells grown under these conditions will be determined thereafter. By generating this data, we aim to better understand microbial responses to perchlorate stress and thereby further elucidate the habitability of martian brines and possibly can propose potential biomarkers for upcoming life detection missions on Mars.

 

References

Hecht MH, Kounaves SP, Quinn RC, West SJ, Young SMM, Ming DW, Catling DC, Clark BC, Boynton W V., Hoffman J, DeFlores LP, Gospodinova K, Kapit J, Smith PH (2009) Detection of perchlorate and the soluble chemistry of martian soil at the phoenix lander site. Science 325:64–67 . doi: 10.1126/science.1172466

Heinz J, Doellinger J, Maus D, Schneider A, Lasch P (2022) Perchlorate-Specific Proteomic Stress Responses of Debaryomyces hansenii Could Enable Microbial Survival in Martian Brines. 1–25, preprint available at bioRxiv, doi: 10.1101/2022.05.02.490276.

Mullakhanbhai MF, Larsen H (1975) Halobacterium volcanii spec. nov., a Dead Sea halobacterium with a moderate salt requirement. Archives of Microbiology 104:207–214 . doi: 10.1007/BF00447326

Oren A, Elevi Bardavid R, Mana L (2014) Perchlorate and halophilic prokaryotes: Implications for possible halophilic life on Mars. Extremophiles 18:75–80 . doi: 10.1007/s00792-013-0594-9

How to cite: Gries, A., Heinz, J., and Schulze-Makuch, D.: Perchlorate stress responses of Haloferax volcanii and implications on the habitability of Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-550, https://doi.org/10.5194/epsc2022-550, 2022.

L2.72
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EPSC2022-692
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ECP
Lea Doris Friedel Kloss, Jacob Heinz, and Dirk Schulze-Makuch

Putative Martian microorganisms could have adapted to the dry, subzero environment of present-day Mars by resorting to hygroscopic salts that might ensure, at least temporarily, the existence of near-surface liquid brines1. Of relevance for this are perchlorates (ClO4-), which are widespread on Mars2 and can absorb atmospheric water in a process called deliquescence while at the same time lowering its freezing point3. However, they might impair microbial life due to the reduction of water activity and ion-specific characteristics harmful to cells such as chaotropicity. As chaotropic agents, perchlorates disrupt the hydrogen bonding network between water molecules and thus the cellular biochemistry by promoting the denaturation of macromolecules.

Within the scope of this study, we aim to identify the perchlorate-specific stress response of the well-established model organism Escherichia coli by exposing the bacterium to sodium perchlorate (NaClO4) while additionally examining other solutes (e.g. glycerol, NaCl, guanidine hydrochloride, and hydrogen peroxide) separately that induce osmotic, ionic, chaotropic, and oxidative stress and comparing the individually occurring cellular responses.

The growth medium DMSZ #1 (0.5% peptone, 0.3% meat extract, pH ~ 7.0) is being used as the basis for aerobic growth of E. coli in liquid cultures at a temperature of 35 °C and is supplemented with the additional solutes of interest for stress induction. E. coli is iteratively adapted to higher solute concentrations to quantify the various solute tolerances of the bacterium which guide further experiments. Cell growth and death are monitored by spectrophotometric measurement of the optical density at a wavelength of 600 nm (OD600), as well as counting colony forming units (CFUs) and changes in cell morphology are observed by light microscopy.

Based on our preliminary results and minimal inhibitory concentrations described in the literature4,5, it seems like E. coli can withstand higher concentrations of NaCl (up to 1 mol/kg) than NaClO4 (up to 0.15 mol/kg). This reduced salt tolerance for NaClO4 compared to NaCl has already been described for other organisms such as the halotolerant yeast Debaryomyces hansenii and could possibly be linked to the chaotropicity of perchlorates, causing macromolecule destabilization6. While final solute tolerances are still being determined, preliminary results suggest that E. coli exhibits a filamentous cell structure at increasing NaClO4 concentrations, with cells clustered together lengthwise in a chain-like arrangement of varying lengths. This change in morphology could potentially be attributed to incomplete cell division7 and is in stark contrast to that of control cells in optimal growth medium, which dominantly appear as individual, rod-like cells. Cell filamentation triggered by NaClO4 exposure has already been observed for the thermophilic and desiccation-tolerant organism Hydrogenothermus marinus8.

We are progressing to more precisely identify the biochemical processes involved in perchlorate-specific stress responses via proteome analysis. In addition, cell filamentation prompts further examinations, such as statistical chain-length evaluation, scanning electron microscope (SEM) imaging and testing for morphological reversibility upon NaClO4-stress removal. Collectively, these results will help us understand the effects of perchlorate-induced stress and thereby allow us to further identify cellular processes critical for life to thrive in and adapt to perchlorate-rich environments like Martian brines.

 

References

1. Davila AF, Schulze-Makuch D. The Last Possible Outposts for Life on Mars. Astrobiology. 2016;16(2):159-168. doi:10.1089/ast.2015.1380

2. Clark BC, Kounaves SP. Evidence for the distribution of perchlorates on Mars. International Journal of Astrobiology. 2016;15(4):311-318. doi:10.1017/S1473550415000385

3. Zorzano M-P, Mateo-Martí E, Prieto-Ballesteros O, Osuna S, Renno N. Stability of liquid saline water on present day Mars. Geophys Res Lett. 2009;36(20). doi:10.1029/2009GL040315

4. Cebrián G, Arroyo C, Mañas P, Condón S. Bacterial maximum non-inhibitory and minimum inhibitory concentrations of different water activity depressing solutes. Int J Food Microbiol. 2014;188:67-74. doi:10.1016/j.ijfoodmicro.2014.07.011

5. Díaz-Rullo J, Rodríguez-Valdecantos G, Torres-Rojas F, et al. Mining for Perchlorate Resistance Genes in Microorganisms From Sediments of a Hypersaline Pond in Atacama Desert, Chile. Front Microbiol. 2021;12:723874. doi:10.3389/fmicb.2021.723874

6. Heinz J, Doellinger J, Maus D, et al. Perchlorate-Specific Proteomic Stress Responses of Debaryomyces hansenii Could Enable Microbial Survival in Martian Brines. preprint available at bioRvix.org. 2022. doi:10.1101/2022.05.02.490276

7. Nguyen K, Kumar P. Morphological Phenotypes, Cell Division, and Gene Expression of Escherichia coli under High Concentration of Sodium Sulfate. Microorganisms. 2022;10(2). doi:10.3390/microorganisms10020274

8. Beblo-Vranesevic K, Huber H, Rettberg P. High Tolerance of Hydrogenothermus marinus to Sodium Perchlorate. Front Microbiol. 2017;8:1369. doi:10.3389/fmicb.2017.01369

How to cite: Kloss, L. D. F., Heinz, J., and Schulze-Makuch, D.: Perchlorate-induced stress responses of Escherichia coli and their implications for the habitability of Mars, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-692, https://doi.org/10.5194/epsc2022-692, 2022.

L2.73
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EPSC2022-912
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ECP
Ines Torres, Elliot Sefton-Nash, and Jorge Vago

Introduction: The ExoMars rover mission, whose primary objective is the search for signs of past and present life on Mars, is an astrobiology focused mission. A suite of nine instruments and a two-metre drill on-board Rosalind Franklin will land in Oxia Planum, a location chosen for its high potential for biosignature preservation (Figure 1). Indeed, the ancient, clay-rich outcrops of Oxia Planum may have formed in aqueous conditions that could have hosted micro-organisms and the fine-grained sediments could have preserved evidence of their existence [1]. Therefore, the probability for in situ biosignature detection would be enhanced in that particular location.

Three “trade-off” tools were designed to evaluate the science potential of targets that Rosalind Franklin will encounter once it lands on Mars. These metrics will be used during operations to aid decision-making for science targets and maximise their scientific value.