Astrobiology最新文献

{"title":"Prebiotic Nucleoside Phosphorylation in a Simulated Deep-Sea Supercritical Carbon Dioxide-Water Two-Phase Environment.","authors":"Shotaro Tagawa, Ryota Hatami, Kohei Morino, Shohei Terazawa, Caner Akıl, Kristin Johnson-Finn, Takazo Shibuya, Kosuke Fujishima","doi":"10.1089/ast.2024.0016","DOIUrl":"https://doi.org/10.1089/ast.2024.0016","url":null,"abstract":"<p><p>Prebiotic synthesis of complex organic molecules in water-rich environments has been a long-standing challenge. In the modern deep sea, emission of liquid CO₂ has been observed in multiple locations, which indicates the existence of benthic CO₂ pools. Recently, a liquid/supercritical CO₂ (ScCO₂) hypothesis has been proposed that a two-phase ScCO₂-water environment could lead to efficient dehydration and condensation of organics. To confirm this hypothesis, we conducted a nucleoside phosphorylation reaction in a hydrothermal reactor creating ScCO₂-water two-phase environment. After 120 h of uridine, cytosine, guanosine, and adenosine phosphorylation at 68.9°C, various nucleoside monophosphates (NMPs), nucleotide diphosphates, and carbamoyl nucleosides were produced. The addition of urea enhanced the overall production of phosphorylated species with 5'-NMPs, the major products that reached over 10% yield. As predicted, phosphorylation did not proceed in the fully aqueous environment without ScCO₂. Further, a glass window reactor was introduced for direct observation of the two-phase environment, where the escape of water into the ScCO₂ phase was observed. These results are similar to those of a wet-dry cycle experiment simulating the terrestrial hot spring environment, indicating that the presence of ScCO₂ can create a comparatively dry condition in the deep sea. In addition, the high acidity present in the aqueous phase further supports nucleotide synthesis by enabling the release of orthophosphate from the hydroxyapatite mineral solving the phosphate problem. Thus, the present study highlights the potential of the unique ScCO₂-water two-phase environment to drive prebiotic nucleotide synthesis and likely induce condensation reactions of various organic and inorganic compounds in the deep-sea CO₂ pool on Earth and potentially other ocean worlds.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142667024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Travel Times of a Descending Melting Probe on Europa.","authors":"Augusto Carballido","doi":"10.1089/ast.2024.0026","DOIUrl":"https://doi.org/10.1089/ast.2024.0026","url":null,"abstract":"<p><p>In this study, we calculated the travel times of a thermal probe that descends through Europa's ice shell. The ice column is simplified to a conductive layer. Using a cellular automaton model, the descent of the probe was simulated by tracking temperature changes, with cell interaction dictated by heat conduction and cell state transition rules determined by cell temperatures. Validation tests, including a soil column simulation, and comparison with experimental data, support the reliability of the model. Simulations were performed with 2 different cell sizes, 19 constant probe temperatures, and 5 ice thermal conductivities. A smaller cell size (<math><mrow><mtext>Δ</mtext><mi>z</mi><mo>=</mo><mn>3</mn><mo> </mo></mrow></math>mm) produced shorter travel times (between 22 days for a probe temperature <math><mrow><mrow><msub><mi>T</mi><mtext>p</mtext></msub></mrow><mo>=</mo><mn>600</mn><mi>K</mi></mrow></math> and ∼4 years for <math><mrow><mrow><msub><mi>T</mi><mtext>p</mtext></msub></mrow><mo>=</mo><mn>280</mn><mi>K</mi></mrow></math>) than a larger cell size (<math><mrow><mtext>Δ</mtext><mi>z</mi><mo>=</mo><mn>1</mn><mo> </mo></mrow></math>m), which produced travel times between 27 years (<math><mrow><mrow><msub><mi>T</mi><mtext>p</mtext></msub></mrow><mo>=</mo></mrow></math> 600K) and ∼10³ years (<math><mrow><mrow><msub><mi>T</mi><mtext>p</mtext></msub></mrow><mo>=</mo></mrow></math> 280K). The ice shell's thermal conductivity has a modest impact on descent times. The results are generally consistent with previous approaches that used more detailed probe engineering considerations. These results suggest that a probe relying solely on heat production may traverse Europa's conductive ice shell within a mission's timeframe.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 11","pages":"1143-1149"},"PeriodicalIF":3.5,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142613894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Venus' Atmospheric Chemistry and Cloud Characteristics Are Compatible with Venusian Life.","authors":"William Bains, Janusz J Petkowski, Sara Seager","doi":"10.1089/ast.2022.0113","DOIUrl":"10.1089/ast.2022.0113","url":null,"abstract":"<p><p>Venus is Earth's sister planet, with similar mass and density but an uninhabitably hot surface, an atmosphere with a water activity 50-100 times lower than anywhere on Earths' surface, and clouds believed to be made of concentrated sulfuric acid. These features have been taken to imply that the chances of finding life on Venus are vanishingly small, with several authors describing Venus' clouds as \"uninhabitable,\" and that apparent signs of life there must therefore be abiotic, or artefactual. In this article, we argue that although many features of Venus can rule out the possibility that Earth life could live there, none rule out the possibility of all life based on what we know of the physical principle of life on Earth. Specifically, there is abundant energy, the energy requirements for retaining water and capturing hydrogen atoms to build biomass are not excessive, defenses against sulfuric acid are conceivable and have terrestrial precedent, and the speculative possibility that life uses concentrated sulfuric acid as a solvent instead of water remains. Metals are likely to be available in limited supply, and the radiation environment is benign. The clouds can support a biomass that could readily be detectable by future astrobiology-focused space missions from its impact on the atmosphere. Although we consider the prospects for finding life on Venus to be speculative, they are not absent. The scientific reward from finding life in such an un-Earthlike environment justifies considering how observations and missions should be designed to be capable of detecting life if it is there.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"371-385"},"PeriodicalIF":4.2,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9618160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DNA Polymerization in Icy Moon Abyssal Pressure Conditions.","authors":"Lorenzo Carré, Ghislaine Henneke, Etienne Henry, Didier Flament, Éric Girard, Bruno Franzetti","doi":"10.1089/ast.2021.0201","DOIUrl":"10.1089/ast.2021.0201","url":null,"abstract":"<p><p>Evidence of stable liquid water oceans beneath the ice crust of moons within the Solar System is of great interest for astrobiology. In particular, subglacial oceans may present hydrothermal processes in their abysses, similarly to terrestrial hydrothermal vents. Therefore, terrestrial extremophilic deep life can be considered a model for putative icy moon extraterrestrial life. However, the comparison between putative extraterrestrial abysses and their terrestrial counterparts suffers from a potentially determinant difference. Indeed, some icy moons oceans may be so deep that the hydrostatic pressure would exceed the maximal pressure at which hydrothermal vent organisms have been isolated. While terrestrial microorganisms that are able to survive in such conditions are known, the effect of high pressure on fundamental biochemical processes is still unclear. In this study, the effects of high hydrostatic pressure on DNA synthesis catalyzed by DNA polymerases are investigated for the first time. The effect on both strand displacement and primer extension activities is measured, and pressure tolerance is compared between enzymes of various thermophilic organisms isolated at different depths.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"151-162"},"PeriodicalIF":4.2,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10495380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Confidence of Life Detection: The Problem of Unconceived Alternatives.","authors":"Peter Vickers, Christopher Cowie, Steven J Dick, Catherine Gillen, Cyrille Jeancolas, Lynn J Rothschild, Sean McMahon","doi":"10.1089/ast.2022.0084","DOIUrl":"10.1089/ast.2022.0084","url":null,"abstract":"Potential biosignatures that offer the promise of extraterrestrial life (past or present) are to be expected in the coming years and decades, whether from within our own solar system, from an exoplanet atmosphere, or otherwise. With each such potential biosignature, the degree of our uncertainty will be the first question asked. Have we really identified extraterrestrial life? How sure are we? This paper considers the problem of unconceived alternative explanations. We stress that articulating our uncertainty requires an assessment of the extent to which we have explored the relevant possibility space. It is argued that, for most conceivable potential biosignatures, we currently have not explored the relevant possibility space very thoroughly at all. Not only does this severely limit the circumstances in which we could reasonably be confident in our detection of extraterrestrial life, it also poses a significant challenge to any attempt to quantify our degree of uncertainty. The discussion leads us to the following recommendation: when it comes specifically to an extraterrestrial life-detection claim, the astrobiology community should follow the uncertainty assessment approach adopted by the Intergovernmental Panel on Climate Change (IPCC).","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"1202-1212"},"PeriodicalIF":4.2,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9942554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microbial Transport by a Descending Ice Melting Probe: Implications for Subglacial and Ocean World Exploration.","authors":"Caleb G Schuler, Dale P Winebrenner, W Timothy Elam, Justin Burnett, Bruce W Boles, Jill A Mikucki","doi":"10.1089/ast.2021.0106","DOIUrl":"10.1089/ast.2021.0106","url":null,"abstract":"<p><p>Ocean Worlds beneath thick ice covers in our solar system, as well as subglacial lakes on Earth, may harbor biological systems. In both cases, thick ice covers (>100 s of meters) present significant barriers to access. Melt probes are emerging as tools for reaching and sampling these realms due to their small logistical footprint, ability to transport payloads, and ease of cleaning in the field. On Earth, glaciers are immured with various abundances of microorganisms and debris. The potential for bioloads to accumulate around and be dragged by a probe during descent has not previously been investigated. Due to the pristine nature of these environments, minimizing and understanding the risk of forward contamination and considering the potential of melt probes to act as instrument-induced special regions are essential. In this study, we examined the effect that two engineering descent strategies for melt probes have on the dragging of bioloads. We also tested the ability of a field cleaning protocol to rid a common contaminant, <i>Bacillus</i>. These tests were conducted in a synthetic ice block immured with bioloads using the Ice Diver melt probe. Our data suggest minimal dragging of bioloads by melt probes, but conclude that modifications for further minimization and use in special regions should be made.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"1153-1164"},"PeriodicalIF":4.2,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10154316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ice Transit and Performance Analysis for Cryorobotic Subglacial Access Missions on Earth and Europa.","authors":"Marc S Boxberg, Qian Chen, Ana-Catalina Plesa, Julia Kowalski","doi":"10.1089/ast.2021.0071","DOIUrl":"10.1089/ast.2021.0071","url":null,"abstract":"<p><p>Ice-covered ocean worlds, such as the Jovian moon Europa, are some of the prime targets for planetary exploration due to their high astrobiological potential. While upcoming space exploration missions, such as the Europa Clipper and JUICE missions, will give us further insight into the local cryoenvironment, any conclusive life detection investigation requires the capability to penetrate and transit the icy shell and access the subglacial ocean directly. Developing robust, autonomous cryorobotic technology for such a mission constitutes an extremely demanding multistakeholder challenge and requires a concentrated interdisciplinary effort between engineers, geoscientists, and astrobiologists. An important tool with which to foster cross-disciplinary work at an early stage of mission preparation is the virtual testbed. In this article, we report on recent progress in the development of an ice transit and performance model for later integration in such a virtual testbed. We introduce a trajectory model that, for the first time, allows for the evaluation of mission-critical parameters, such as transit time and average/overall power supply. Our workflow is applied to selected, existing cryobot designs while taking into consideration different terrestrial, as well as extraterrestrial, deployment scenarios. Specific analyses presented in this study show the tradeoff minimum transit time and maximum efficiency of a cryobot and allow for quantification of different sources of uncertainty to cryobot's trajectory models.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"1135-1152"},"PeriodicalIF":4.2,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10444315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Organic Catalytic Activity as a Method for Agnostic Life Detection.","authors":"Christos D Georgiou, Christopher McKay, Jean-Louis Reymond","doi":"10.1089/ast.2023.0022","DOIUrl":"10.1089/ast.2023.0022","url":null,"abstract":"<p><p>An ideal life detection instrument would have high sensitivity but be insensitive to abiotic processes and would be capable of detecting life with alternate molecular structures. In this study, we propose that catalytic activity can be the basis of a nearly ideal life detection instrument. There are several advantages to catalysis as an agnostic life detection method. Demonstrating catalysis does not necessarily require culturing/growing the alien life and in fact may persist even in dead biomass for some time, and the amplification by catalysis is large even by minute amounts of catalysts and, hence, can be readily detected against abiotic background rates. In specific, we propose a hydrolytic catalysis detection instrument that could detect activity in samples of extraterrestrial organic material from unknown life. The instrument uses chromogenic assay-based detection of various hydrolytic catalytic activities, which are matched to corresponding artificial substrates having the same, chromogenic (preferably fluorescent) upon release, group; D- and L-enantiomers of these substrates can be used to also answer the question whether unknown life is chiral. Since catalysis is a time-proportional product-concentration amplification process, hydrolytic catalytic activity can be measured on a sample of even a minute size, and with instruments based on, for example, optofluidic chip technology.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"1118-1127"},"PeriodicalIF":4.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9901996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Life Detection on Icy Moons Using Flow Cytometry and Exogenous Fluorescent Stains.","authors":"Matthew L Wallace,&nbsp;Nicholas Tallarida,&nbsp;Wayne W Schubert,&nbsp;James Lambert","doi":"10.1089/ast.2023.0016","DOIUrl":"10.1089/ast.2023.0016","url":null,"abstract":"<p><p>Flow cytometry is a potential technology for <i>in situ</i> life detection on icy moons (such as Enceladus and Europa) and on the polar ice caps of Mars. We developed a method for using flow cytometry to positively identify four classes of biomarkers using exogenous fluorescent stains: nucleic acids, proteins, carbohydrates, and lipids. We demonstrated the effectiveness of exogenous stains with six known organisms and known abiotic material and showed that the cytometer is easily able to distinguish between the known organisms and the known abiotic material using the exogenous stains. To simulate a life-detection experiment on an icy world lander, we used six natural samples with unknown biotic and abiotic content. We showed that flow cytometry can identify all four biomarkers using the exogenous stains and can separate the biotic material from the known abiotic material on scatter plots. Exogenous staining techniques would likely be used in conjunction with intrinsic fluorescence, clustering, and sorting for a more complete and capable life-detection instrument on an icy moon lander.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"1071-1082"},"PeriodicalIF":4.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10160741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inducing Homochirality Through Intermediary Catalytic Species: A Stochastic Approach.","authors":"Osmel Martín, Yoelsy Leyva, José Suárez-Lezcano, Yunierkis Pérez-Castillo, Yovani Marrero-Ponce","doi":"10.1089/ast.2023.0004","DOIUrl":"10.1089/ast.2023.0004","url":null,"abstract":"<p><p>A new chiral amplification mechanism based on a stochastic approach is proposed. The mechanism includes five different chemical species, an achiral substrate (A), two chiral forms (L, D), and two intermediary species (LA, DA). The process occurs within a small, semipermeable compartment that can be diffusively coupled with the outside environment. The study considers two alternative primary sources for chiral species within the compartment, one chemical and the other diffusive. As a remarkable fact, the chiral amplification process occurs due to stochastic fluctuations of an intermediary catalytic species (LA, DA) produced <i>in situ,</i> given the interaction of the chiral species with the achiral substrate. The net process includes two different steps: the synthesis of the catalyst (LA and DA) and the catalytic production of new chiral species from the substrate. Stochastic simulations show that proper parameterization can induce a robust chiral state within the compartment regardless of whether the system is open or closed. We also show how an increase in the non-catalytic production of chiral species tends to negatively impact the homochirality degree of the system. By its conception, the proposed mechanism suggests a deeper connection with how most biochemical processes occur in living beings, a fact that could open new avenues for studying this fascinating phenomenon.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"1083-1089"},"PeriodicalIF":4.2,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10128851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}