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  • 1.
    Cataldi, Gianni
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Brandeker, Alexis
    Stockholm University, Faculty of Science, Department of Astronomy.
    Thébault, Philippe
    Ahmed, Engy
    de Vries, Bernard L.
    Neubeck, Anna
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Singer, Kelsi
    Searching for biosignatures in exoplanetary impact ejectaIn: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070Article in journal (Refereed)
  • 2.
    Cataldi, Gianni
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Brandeker, Alexis
    Stockholm University, Faculty of Science, Department of Astronomy.
    Thébault, Philippe
    Singer, Kelsi
    Ahmed, Engy
    Stockholm University, Faculty of Science, Department of Geological Sciences. Royal Institute of Technology (KTH), Sweden.
    de Vries, Bernard L.
    Stockholm University, Faculty of Science, Department of Astronomy. European Space Research and Technology Centre (ESA/ESTEC), The Netherlands.
    Neubeck, Anna
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Searching for Biosignatures in Exoplanetary Impact Ejecta2017In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, no 8, p. 721-746Article in journal (Refereed)
    Abstract [en]

    With the number of confirmed rocky exoplanets increasing steadily, their characterization and the search for exoplanetary biospheres are becoming increasingly urgent issues in astrobiology. To date, most efforts have concentrated on the study of exoplanetary atmospheres. Instead, we aim to investigate the possibility of characterizing an exoplanet (in terms of habitability, geology, presence of life, etc.) by studying material ejected from the surface during an impact event. For a number of impact scenarios, we estimate the escaping mass and assess its subsequent collisional evolution in a circumstellar orbit, assuming a Sun-like host star. We calculate the fractional luminosity of the dust as a function of time after the impact event and study its detectability with current and future instrumentation. We consider the possibility to constrain the dust composition, giving information on the geology or the presence of a biosphere. As examples, we investigate whether calcite, silica, or ejected microorganisms could be detected. For a 20km diameter impactor, we find that the dust mass escaping the exoplanet is roughly comparable to the zodiacal dust, depending on the exoplanet's size. The collisional evolution is best modeled by considering two independent dust populations, a spalled population consisting of nonmelted ejecta evolving on timescales of millions of years, and dust recondensed from melt or vapor evolving on much shorter timescales. While the presence of dust can potentially be inferred with current telescopes, studying its composition requires advanced instrumentation not yet available. The direct detection of biological matter turns out to be extremely challenging. Despite considerable difficulties (small dust masses, noise such as exozodiacal dust, etc.), studying dusty material ejected from an exoplanetary surface might become an interesting complement to atmospheric studies in the future.

  • 3. Gentry, Diana M.
    et al.
    Amador, Elena S.
    Cable, Morgan L.
    Chaudry, Nosheen
    Cullen, Thomas
    Jacobsen, Malene B.
    Murukesan, Gayathri
    Schwieterman, Edward W.
    Stevens, Adam H.
    Stockton, Amanda
    Tan, George
    Yin, Chang
    Stockholm University, Faculty of Science, Department of Physics.
    Cullen, David C.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Correlations Between Life-Detection Techniques and Implications for Sampling Site Selection in Planetary Analog Missions2017In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, no 10, p. 1009-1021Article in journal (Refereed)
    Abstract [en]

    We conducted an analog sampling expedition under simulated mission constraints to areas dominated by basaltic tephra of the Eldfell and Fimmvorouhals lava fields (Iceland). Sites were selected to be homogeneous at a coarse remote sensing resolution (10-100m) in apparent color, morphology, moisture, and grain size, with best-effort realism in numbers of locations and replicates. Three different biomarker assays (counting of nucleic-acid-stained cells via fluorescent microscopy, a luciferin/luciferase assay for adenosine triphosphate, and quantitative polymerase chain reaction (qPCR) to detect DNA associated with bacteria, archaea, and fungi) were characterized at four nested spatial scales (1m, 10m, 100m, and >1km) by using five common metrics for sample site representativeness (sample mean variance, group F tests, pairwise t tests, and the distribution-free rank sum H and u tests). Correlations between all assays were characterized with Spearman's rank test. The bioluminescence assay showed the most variance across the sites, followed by qPCR for bacterial and archaeal DNA; these results could not be considered representative at the finest resolution tested (1m). Cell concentration and fungal DNA also had significant local variation, but they were homogeneous over scales of >1km. These results show that the selection of life detection assays and the number, distribution, and location of sampling sites in a low biomass environment with limited a priori characterization can yield both contrasting and complementary results, and that their interdependence must be given due consideration to maximize science return in future biomarker sampling expeditions.

  • 4.
    Holm, Nils G.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Oze, C.
    Mousis, O.
    Waite, J. H.
    Guilbert-Lepoutre, A.
    Serpentinization and the Formation of H-2 and CH4 on Celestial Bodies (Planets, Moons, Comets)2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, no 7, p. 587-600Article, review/survey (Refereed)
    Abstract [en]

    Serpentinization involves the hydrolysis and transformation of primary ferromagnesian minerals such as olivine ((Mg,Fe)(2)SiO4) and pyroxenes ((Mg,Fe)SiO3) to produce H-2-rich fluids and a variety of secondary minerals over a wide range of environmental conditions. The continual and elevated production of H-2 is capable of reducing carbon, thus initiating an inorganic pathway to produce organic compounds. The production of H-2 and H-2-dependent CH4 in serpentinization systems has received significant interdisciplinary interest, especially with regard to the abiotic synthesis of organic compounds and the origins and maintenance of life in Earth's lithosphere and elsewhere in the Universe. Here, serpentinization with an emphasis on the formation of H-2 and CH4 are reviewed within the context of the mineralogy, temperature/pressure, and fluid/gas chemistry present in planetary environments. Whether deep in Earth's interior or in Kuiper Belt Objects in space, serpentinization is a feasible process to invoke as a means of producing astrobiologically indispensable H-2 capable of reducing carbon to organic compounds.

  • 5.
    Holm, Nils
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Introduction to a Series of Articles That Focus on Methane2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, no 4, p. 307-307Article, review/survey (Refereed)
  • 6. Ivarsson, Magnus
    et al.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Holmström, Sara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ahlbom, Marianne
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lindblom, Sten
    Holm, Nils
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Putative fossilized fungi from the lithified volcaniclastic apron of Gran Canaria, Spain2011In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 11, no 7, p. 633-650Article in journal (Refereed)
    Abstract [en]

    We report the discovery of fossilized filamentous structures in samples of the lithified, volcaniclastic apron of Gran Canaria, which were obtained during Leg 157 of the Ocean Drilling Program (ODP). These filamentous structures are 2–15 μm in diameter and several hundred micrometers in length and are composed of Si, Al, Fe, Ca, Mg, Na, Ti, and C. Chitin was detected in the filamentous structures by staining with wheat germ agglutinin dye conjugated with fluorescein isothiocyanate (WGA-FITC), which suggests that they are fossilized fungal hyphae. The further elucidation of typical filamentous fungal morphological features, such as septa, hyphal bridges, and anastomosis and their respective sizes, support this interpretation. Characteristic structures that we interpreted as fossilized spores were also observed in association with the putative hyphae. The fungal hyphae were found in pyroxene phenocrysts and in siderite pseudomorphs of a basalt breccia. The fungal colonization of the basalt clasts occurred after the brecciation but prior to the final emplacement and lithification of the sediment at 16–14 Ma. The siderite appears to have been partially dissolved by the presence of fungal hyphae, and the fungi preferentially colonized Fe-rich carbonates over Fe-poor carbonates (aragonite). Our findings indicate that fungi may be an important geobiological agent in subseafloor environments and an important component of the deep subseafloor biosphere, and that hydrothermal environments associated with volcanism can support a diverse ecosystem, including eukaryotes.

  • 7. Jonsson, K. Ingemar
    et al.
    Wojcik, Andrzej
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Tolerance to X-rays and Heavy Ions (Fe, He) in the Tardigrade Richtersius coronifer and the Bdelloid Rotifer Mniobia russeola2017In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, no 2, p. 163-167Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to analyze tolerance to heavy ions in desiccated animals of the eutardigrade Richtersius coronifer and the bdelloid rotifer Mniobia russeola within the STARLIFE project. Both species were exposed to iron (Fe) and helium (He) ions at the Heavy Ion Medical Accelerator in Chiba (HIMAC) in Chiba, Japan, and to X-rays at the German Aerospace Center (DLR) in Cologne, Germany. Results show no effect of Fe and He on viability up to 7 days post-rehydration in both R. coronifer and M. russeola, while X-rays tended to reduce viability in R. coronifer at the highest doses. Mean egg production rate tended to decline with higher doses in R. coronifer for all radiation types, but the pattern was not statistically confirmed. In M. russeola, there was no such tendency for a dose response in egg production rate. These results confirm the previously reported high tolerance to high linear energy transfer (LET) radiation in tardigrades and show for the first time that bdelloid rotifers are also very tolerant to high-LET radiation. These animal phyla represent the most desiccation-and radiation-tolerant animals on Earth and provide excellent eukaryotic models for astrobiological research.

  • 8. Kobayashi, Kensei
    et al.
    Geppert, Wolf D.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Carrasco, Nathalie
    Holm, Nils G.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mousis, Olivier
    Palumbo, Maria Elisabetta
    Waite, J. Hunter
    Watanabe, Naoki
    Ziurys, Lucy M.
    Laboratory Studies of Methane and Its Relationship to Prebiotic Chemistry2017In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, no 8, p. 786-812Article, review/survey (Refereed)
    Abstract [en]

    To examine how prebiotic chemical evolution took place on Earth prior to the emergence of life, laboratory experiments have been conducted since the 1950s. Methane has been one of the key molecules in these investigations. In earlier studies, strongly reducing gas mixtures containing methane and ammonia were used to simulate possible reactions in the primitive atmosphere of Earth, producing amino acids and other organic compounds. Since Earth's early atmosphere is now considered to be less reducing, the contribution of extraterrestrial organics to chemical evolution has taken on an important role. Such organic molecules may have come from molecular clouds and regions of star formation that created protoplanetary disks, planets, asteroids, and comets. The interstellar origin of organics has been examined both experimentally and theoretically, including laboratory investigations that simulate interstellar molecular reactions. Endogenous and exogenous organics could also have been supplied to the primitive ocean, making submarine hydrothermal systems plausible sites of the generation of life. Experiments that simulate such hydrothermal systems where methane played an important role have consequently been conducted. Processes that occur in other Solar System bodies offer clues to the prebiotic chemistry of Earth. Titan and other icy bodies, where methane plays significant roles, are especially good targets. In the case of Titan, methane is both in the atmosphere and in liquidospheres that are composed of methane and other hydrocarbons, and these have been studied in simulation experiments. Here, we review the wide range of experimental work in which these various terrestrial and extraterrestrial environments have been modeled, and we examine the possible role of methane in chemical evolution.

  • 9. Konn, C.
    et al.
    Charlou, J. L.
    Holm, Nils G.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mousis, O.
    The Production of Methane, Hydrogen, and Organic Compounds in Ultramafic-Hosted Hydrothermal Vents of the Mid-Atlantic Ridge2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, no 5, p. 381-399Article, review/survey (Refereed)
    Abstract [en]

    Both hydrogen and methane are consistently discharged in large quantities in hydrothermal fluids issued from ultramafic-hosted hydrothermal fields discovered along the Mid-Atlantic Ridge. Considering the vast number of these fields discovered or inferred, hydrothermal fluxes represent a significant input of H-2 and CH4 to the ocean. Although there are lines of evidence of their abiogenic formation from stable C and H isotope results, laboratory experiments, and thermodynamic data, neither their origin nor the reaction pathways generating these gases have been fully constrained yet. Organic compounds detected in the fluids may also be derived from abiotic reactions. Although thermodynamics are favorable and extensive experimental work has been done on Fischer-Tropsch-type reactions, for instance, nothing is clear yet about their origin and formation mechanism from actual data. Since chemolithotrophic microbial communities commonly colonize hydrothermal vents, biogenic and thermogenic processes are likely to contribute to the production of H-2, CH4, and other organic compounds. There seems to be a consensus toward a mixed origin (both sources and processes) that is consistent with the ambiguous nature of the isotopic data. But the question that remains is, to what proportions? More systematic experiments as well as integrated geochemical approaches are needed to disentangle hydrothermal geochemistry. This understanding is of prime importance considering the implications of hydrothermal H-2, CH4, and organic compounds for the ocean global budget, global cycles, and the origin of life.

  • 10. Mousis, Olivier
    et al.
    Chassefiere, Eric
    Holm, Nils G.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bouquet, Alexis
    Hunter Waite, Jack
    Geppert, Wolf Dietrich
    Stockholm University, Faculty of Science, Department of Physics.
    Picaud, Sylvain
    Aikawa, Yuri
    Ali-Dib, Mohamad
    Charlou, Jean-Luc
    Rousselot, Philippe
    Methane Clathrates in the Solar System2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, no 4, p. 308-326Article, review/survey (Refereed)
    Abstract [en]

    We review the reservoirs of methane clathrates that may exist in the different bodies of the Solar System. Methane was formed in the interstellar medium prior to having been embedded in the protosolar nebula gas phase. This molecule was subsequently trapped in clathrates that formed from crystalline water ice during the cooling of the disk and incorporated in this form into the building blocks of comets, icy bodies, and giant planets. Methane clathrates may play an important role in the evolution of planetary atmospheres. On Earth, the production of methane in clathrates is essentially biological, and these compounds are mostly found in permafrost regions or in the sediments of continental shelves. On Mars, methane would more likely derive from hydrothermal reactions with olivine-rich material. If they do exist, martian methane clathrates would be stable only at depth in the cryosphere and sporadically release some methane into the atmosphere via mechanisms that remain to be determined. In the case of Titan, most of its methane probably originates from the protosolar nebula, where it would have been trapped in the clathrates agglomerated by the satellite's building blocks. Methane clathrates are still believed to play an important role in the present state of Titan. Their presence is invoked in the satellite's subsurface as a means of replenishing its atmosphere with methane via outgassing episodes. The internal oceans of Enceladus and Europa also provide appropriate thermodynamic conditions that allow formation of methane clathrates. In turn, these clathrates might influence the composition of these liquid reservoirs. Finally, comets and Kuiper Belt Objects might have formed from the agglomeration of clathrates and pure ices in the nebula. The methane observed in comets would then result from the destabilization of clathrate layers in the nuclei concurrent with their approach to perihelion. Thermodynamic equilibrium calculations show that methane-rich clathrate layers may exist on Pluto as well.

  • 11.
    Poole, Anthony M.
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biology and Functional Genomics.
    Willerslev, Eske
    Can identification of a fourth domain of life be made from sequence data alone, and could it be done on mars?2007In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 7, no 5, p. 801-814Article, review/survey (Refereed)
    Abstract [en]

    A central question in astrobiology is whether life exists elsewhere in the universe. If so, is it related to Earth life? Technologies exist that enable identification of DNA- or RNA-based microbial life directly from environmental samples here on Earth. Such technologies could, in principle, be applied to the search for life elsewhere; indeed, efforts are underway to initiate such a search. However, surveying for nucleic acid-based life on other planets, if attempted, must be carried out with caution, owing to the risk of contamination by Earth-based life. Here we argue that the null hypothesis must be that any DNA discovered and sequenced from samples taken elsewhere in the universe are Earth-based contaminants. Experience from studies of low-biomass ancient DNA demonstrates that some results, by their very nature, will not enable complete rejection of the null hypothesis. In terms of eliminating contamination as an explanation of the data, there may be value in identification of sequences that lie outside the known diversity of the three domains of life. We therefore have examined whether a fourth domain could be readily identified from environmental DNA sequence data alone. We concluded that, even on Earth, this would be far from trivial, and we illustrate this point by way of examples drawn from the literature. Overall, our conclusions do not bode well for planned PCR-based surveys for life on Mars, and we argue that other independent biosignatures will be essential in corroborating any claims for the presence of life based on nucleic acid sequences.

  • 12. Tulej, Marek
    et al.
    Neubeck, Anna
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ivarsson, Magnus
    Riedo, Andreas
    Neuland, Maike B.
    Meyer, Stefan
    Wurz, Peter
    Chemical Composition of Micrometer-Sized Filaments in an Aragonite Host by a Miniature Laser Ablation/Ionization Mass Spectrometer2015In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 15, no 8, p. 669-682Article in journal (Refereed)
    Abstract [en]

    Detection of extraterrestrial life is an ongoing goal in space exploration, and there is a need for advanced instruments and methods for the detection of signatures of life based on chemical and isotopic composition. Here, we present the first investigation of chemical composition of putative microfossils in natural samples using a miniature laser ablation/ionization time-of-flight mass spectrometer (LMS). The studies were conducted with high lateral (similar to 15 mu m) and vertical (similar to 20-200 nm) resolution. The primary aim of the study was to investigate the instrument performance on micrometer-sized samples both in terms of isotope abundance and element composition. The following objectives had to be achieved: (1) Consider the detection and calculation of single stable isotope ratios in natural rock samples with techniques compatible with their employment of space instrumentation for biomarker detection in future planetary missions. (2) Achieve a highly accurate chemical compositional map of rock samples with embedded structures at the micrometer scale in which the rock matrix is easily distinguished from the micrometer structures. Our results indicate that chemical mapping of strongly heterogeneous rock samples can be obtained with a high accuracy, whereas the requirements for isotope ratios need to be improved to reach sufficiently large signal-to-noise ratio (SNR). Key Words: Biogenicity-Biomarkers-Biosignatures-Filaments-Fossilization. Astrobiology 15, 669-682.

  • 13. Wiesendanger, Reto
    et al.
    Wacey, David
    Tulej, Marek
    Neubeck, Anna
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ivarsson, Magnus
    Grimaudo, Valentine
    Moreno-Garcia, Pavel
    Cedeno-Lopez, Alena
    Riedo, Andreas
    Wurz, Peter
    Chemical and Optical Identification of Micrometer-Sized 1.9 Billion-Year-Old Fossils by Combining a Miniature Laser Ablation Ionization Mass Spectrometry System with an Optical Microscope2018In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 18, no 8, p. 1071-1080Article in journal (Refereed)
    Abstract [en]

    The recognition of biosignatures on planetary bodies requires the analysis of the putative microfossil with a set of complementary analytical techniques. This includes localized elemental and isotopic analysis of both, the putative microfossil and its surrounding host matrix. If the analysis can be performed with spatial resolution at the micrometer level and ppm detection sensitivities, valuable information on the (bio)chemical and physical processes that influenced the sample material can be gained. Our miniaturized laser ablation ionization mass spectrometry (LIMS)-time-of-flight mass spectrometer instrument is a valid candidate for performing the required chemical analysis in situ. However, up until now it was limited by the spatial accuracy of the sampling. In this contribution, we introduce a newly developed microscope system with micrometer accuracy for Ultra High Vacuum application, which allows a significant increase in the measurement capabilities of our miniature LIMS system. The new enhancement allows identification and efficient and accurate sampling of features of micrometer-sized fossils in a host matrix. The performance of our system is demonstrated by the identification and chemical analysis of signatures of micrometer-sized fossil structures in the 1.9 billion-year-old Gunflint chert.

  • 14. Ziurys, L. M.
    et al.
    Halfen, D. T.
    Geppert, Wolf
    Stockholm University, Faculty of Science, Department of Physics.
    Aikawa, Y.
    Following the Interstellar History of Carbon: From the Interiors of Stars to the Surfaces of Planets2016In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 16, no 12, p. 997-1012Article in journal (Refereed)
    Abstract [en]

    The chemical history of carbon is traced from its origin in stellar nucleosynthesis to its delivery to planet surfaces. The molecular carriers of this element are examined at each stage in the cycling of interstellar organic material and their eventual incorporation into solar system bodies. The connection between the various interstellar carbon reservoirs is also examined. Carbon has two stellar sources: supernova explosions and mass loss from evolved stars. In the latter case, the carbon is dredged up from the interior and then ejected into a circumstellar envelope, where a rich and unusual C-based chemistry occurs. This molecular material is eventually released into the general interstellar medium through planetary nebulae. It is first incorporated into diffuse clouds, where carbon is found in polyatomic molecules such as H2CO, HCN, HNC, c-C3H2, and even C-60(+). These objects then collapse into dense clouds, the sites of star and planet formation. Such clouds foster an active organic chemistry, producing compounds with a wide range of functional groups with both gas-phase and surface mechanisms. As stars and planets form, the chemical composition is altered by increasing stellar radiation, as well as possibly by reactions in the presolar nebula. Some molecular, carbon-rich material remains pristine, however, encapsulated in comets, meteorites, and interplanetary dust particles, and is delivered to planet surfaces.

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