Astrobiology最新文献

{"title":"Eta-Earth Revisited II: Deriving a Maximum Number of Earth-Like Habitats in the Galactic Disk.","authors":"Manuel Scherf, Helmut Lammer, Laurenz Spross","doi":"10.1089/ast.2023.0076","DOIUrl":"10.1089/ast.2023.0076","url":null,"abstract":"<p><p>In Lammer et al. (2024), we defined Earth-like habitats (EHs) as rocky exoplanets within the habitable zone of complex life (HZCL) on which Earth-like N<sub>2</sub>-O<sub>2</sub>-dominated atmospheres with minor amounts of CO<sub>2</sub> can exist, and derived a formulation for estimating the maximum number of EHs in the galaxy given realistic probabilistic requirements that have to be met for an EH to evolve. In this study, we apply this formulation to the galactic disk by considering only requirements that are already scientifically quantifiable. By implementing literature models for star formation rate, initial mass function, and the mass distribution of the Milky Way, we calculate the spatial distribution of disk stars as functions of stellar mass and birth age. For the stellar part of our formulation, we apply existing models for the galactic habitable zone and evaluate the thermal stability of nitrogen-dominated atmospheres with different CO<sub>2</sub> mixing ratios inside the HZCL by implementing the newest stellar evolution and upper atmosphere models. For the planetary part, we include the frequency of rocky exoplanets, the availability of surface water and subaerial land, and the potential requirement of hosting a large moon by evaluating their importance and implementing these criteria from minima to maxima values as found in the scientific literature. We also discuss further factors that are not yet scientifically quantifiable but may be requirements for EHs to evolve. Based on such an approach, we find that EHs are relatively rare by obtaining plausible maximum numbers of <math><mrow><msubsup><mrow><mn>2.5</mn></mrow><mrow><mo>-</mo><mn>2.4</mn></mrow><mrow><mo>+</mo><mn>71.6</mn></mrow></msubsup><mo>×</mo><msup><mrow><mn>10</mn></mrow><mn>5</mn></msup></mrow></math> and <math><mrow><msubsup><mrow><mn>0.6</mn></mrow><mrow><mo>-</mo><mn>0.59</mn></mrow><mrow><mo>+</mo><mn>27.1</mn></mrow></msubsup><mo>×</mo><msup><mrow><mn>10</mn></mrow><mn>5</mn></msup></mrow></math>planets that can potentially host N<sub>2</sub>-O<sub>2</sub>-dominated atmospheres with maximum CO<sub>2</sub> mixing ratios of 10% and 1%, respectively, implying that, on average, a minimum of <math><mrow><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mn>3</mn></msup><mo>-</mo><msup><mrow><mn>10</mn></mrow><mn>6</mn></msup></mrow></math>rocky exoplanets in the HZCL are needed for 1 EH to evolve. The actual number of EHs, however, may be substantially lower than our maximum ranges since several requirements with unknown occurrence rates are not included in our model (<i>e.g.</i>, the origin of life, working carbon-silicate and nitrogen cycles); this also implies extraterrestrial intelligence (ETI) to be significantly rarer still. Our results illustrate that not every star can host EHs nor can each rocky exoplanet within the HZCL evolve such that it might be able to host complex animal-like life or even ETIs. The Copernican Principle of Mediocrity therefore cannot be app","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 10","pages":"e916-e1061"},"PeriodicalIF":3.5,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142557027","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":"Eta-Earth Revisited I: A Formula for Estimating the Maximum Number of Earth-Like Habitats.","authors":"Helmut Lammer, Manuel Scherf, Laurenz Sproß","doi":"10.1089/ast.2023.0075","DOIUrl":"10.1089/ast.2023.0075","url":null,"abstract":"<p><p>In this hypothesis article, we discuss the basic requirements of planetary environments where aerobe organisms can grow and survive, including atmospheric limitations of millimeter-to-meter-sized biological animal life based on physical limits and O₂, N₂, and CO₂ toxicity levels. By assuming that animal-like extraterrestrial organisms adhere to similar limits, we define Earth-like habitats (EH) as rocky exoplanets in the habitable zone for complex life that host N₂-O₂-dominated atmospheres with minor amounts of CO₂, at which advanced animal-like life or potentially even extraterrestrial intelligent life can in principle evolve and exist. We then derive a new formula that can be used to estimate the maximum occurrence rate of such Earth-like habitats in the Galaxy. This contains realistic probabilistic arguments that can be fine-tuned and constrained by atmospheric characterization with future space and ground-based telescopes. As an example, we briefly discuss two specific requirements feeding into our new formula that, although not quantifiable at present, will become scientifically quantifiable in the upcoming decades due to future observations of exoplanets and their atmospheres. Key Words: Eta-Earth-Earth-like habitats-oxygenation time-nitrogen atmospheres-carbon dioxide-animal-like life. Astrobiology 24, 897-915.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 10","pages":"897-915"},"PeriodicalIF":3.5,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142557026","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":"Timing and Likelihood of the Origin of Life Derived from Post-Impact Highly Reducing Atmospheres.","authors":"Nicholas F Wogan, David C Catling, Kevin J Zahnle","doi":"10.1089/ast.2023.0128","DOIUrl":"https://doi.org/10.1089/ast.2023.0128","url":null,"abstract":"<p><p>Big impacts on the early Earth would have created highly reducing atmospheres that generated molecules needed for the origin of life, such as nitriles. However, such impactors could have been followed by collisions that were sufficiently big to vaporize the ocean and destroy any pre-existing life. Thus, a post-impact-reducing atmosphere that gives rise to life needs to be followed by a lack of subsequent sterilizing impacts for life to persist. We assume that prebiotic chemistry required a post-impact-reducing atmosphere. Then, using statistics for the impact history on Earth and the minimum impact mass needed to generate post-impact highly reducing atmospheres, we show that the median timing of impact-driven biopoiesis is favored early in the Hadean, ∼4.35 Ga. However, uncertainties are large because impact bombardment is stochastic, and so biopoiesis could have occurred between 4.45 and 3.9 Ga within 95% uncertainty. In an optimistic scenario for biopoiesis from post-impact-reducing atmospheres, we find that the origin of life is favorable in ∼90% of stochastic impact realizations. In our most pessimistic case, biopoiesis is still fairly likely (∼20% chance). This potentially bodes well for life on rocky exoplanets that have experienced an early episode of impact bombardment given how planets form.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 9","pages":"881-891"},"PeriodicalIF":3.5,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142340212","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":"Rosalind Franklin Society Proudly Announces the 2023 Award Recipient for <i>Astrobiology</i>.","authors":"Trishool Namani","doi":"10.1089/ast.2024.67345.rfs2023","DOIUrl":"https://doi.org/10.1089/ast.2024.67345.rfs2023","url":null,"abstract":"","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 9","pages":"855"},"PeriodicalIF":3.5,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142340210","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":"Self-Oxidation of the Atmospheres of Rocky Planets with Implications for the Origin of Life.","authors":"Anders Johansen, Eloi Camprubi, Elishevah van Kooten, H Jens Hoeijmakers","doi":"10.1089/ast.2023.0104","DOIUrl":"https://doi.org/10.1089/ast.2023.0104","url":null,"abstract":"<p><p>Rocky planets may acquire a primordial atmosphere by the outgassing of volatiles from their magma ocean. The distribution of O between H₂O, CO, and CO₂ in chemical equilibrium subsequently changes significantly with decreasing temperature. We consider here two chemical models: one where CH₄ and NH₃ are assumed to be irrevocably destroyed by photolysis and second where these molecules persist. In the first case, we show that CO cannot coexist with H₂O, since CO oxidizes at low temperatures to form CO₂ and H₂. In both cases, H escapes from the thermosphere within a few 10 million years by absorption of stellar XUV radiation. This escape drives an atmospheric self-oxidation process, whereby rocky planet atmospheres become dominated by CO₂ and H₂O regardless of their initial oxidation state at outgassing. HCN is considered a potential precursor of prebiotic compounds and RNA. Oxidizing atmospheres are inefficient at producing HCN by lightning. Alternatively, we have demonstrated that lightning-produced NO, which dissolves as nitrate in oceans, and interplanetary dust particles may be the main sources of fixed nitrogen in emerging biospheres. Our results highlight the need for origin-of-life scenarios where the first metabolism fixes its C from CO₂, rather than from HCN and CO.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 9","pages":"856-880"},"PeriodicalIF":3.5,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142340211","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":"Ultraviolet Resistance of Microorganisms Isolated from Uranium-Rich Minerals from Perus, Brazil.","authors":"Bárbara Poletto, Gabriel Gonçalves Silva, Ana Carolina Souza Ramos de Carvalho, Roberta Almeida Vincenzi, Eiji Yamassaki de Almeida, Douglas Galante, Amanda Gonçalves Bendia, Fabio Rodrigues","doi":"10.1089/ast.2022.0125","DOIUrl":"10.1089/ast.2022.0125","url":null,"abstract":"<p><p>The district of Perus, located in the city of São Paulo, Brazil, is renowned for its weathered granitic-pegmatitic masses, which harbor a significant number of uraniferous minerals that contribute to ionizing radiation levels up to 20 times higher than the background levels. In this study, aseptically collected mineral samples from the area were utilized to isolate 15 microorganisms, which were subjected to pre-screening tests involving UV-C and UV-B radiation. The microorganisms that exhibited the highest resistance to ultraviolet (UV) radiation were selected for the construction of survival curves for UV-C, broad-band UV-B, and solar simulation resistance testing. Subsequently, the four strains that demonstrated superior survival capabilities under UV radiation exposure were chosen for 16S rRNA gene sequencing. Among these, <i>Nocardioides</i> sp. O4R and <i>Nocardioides</i> sp. MA2R demonstrated the most promising outcomes in the UV radiation resistance assessments, showcasing comparable performance to the well-established radioresistant model organism <i>Deinococcus radiodurans</i>. These findings underscore the potential of naturally occurring high-radiation environments as valuable resources for the investigation of UV-resistant microorganisms. Astrobiology 24, 783-794.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"783-794"},"PeriodicalIF":3.5,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141295434","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":"Investigating Polyextremophilic Bacteria in Al Wahbah Crater, Saudi Arabia: A Terrestrial Model for Life on Saturn's Moon Enceladus.","authors":"Alef Dos Santos, Júnia Schultz, Marilia Almeida Trapp, Fluvio Modolon, Andrii Romanenko, Arun Kumar Jaiswal, Lucas Gomes, Edson Rodrigues-Filho, Alexandre Soares Rosado","doi":"10.1089/ast.2024.0017","DOIUrl":"https://doi.org/10.1089/ast.2024.0017","url":null,"abstract":"<p><p>The study of extremophilic microorganisms has sparked interest in understanding extraterrestrial microbial life. Such organisms are fundamental for investigating life forms on Saturn's icy moons, such as Enceladus, which is characterized by potentially habitable saline and alkaline niches. Our study focused on the salt-alkaline soil of the Al Wahbah crater in Saudi Arabia, where we identified microorganisms that could be used as biological models to understand potential life on Enceladus. The search involved isolating 48 bacterial strains, sequencing the genomes of two thermo-haloalkaliphilic strains, and characterizing them for astrobiological application. A deeper understanding of the genetic composition and functional capabilities of the two novel strains of <i>Halalkalibacterium halodurans</i> provided valuable insights into their survival strategies and the presence of coding genes and pathways related to adaptations to environmental stressors. We also used mass spectrometry with a molecular network approach, highlighting various classes of molecules, such as phospholipids and nonproteinogenic amino acids, as potential biosignatures. These are essential features for understanding life's adaptability under extreme conditions and could be used as targets for biosignatures in upcoming missions exploring Enceladus' orbit. Furthermore, our study reinforces the need to look at new extreme environments on Earth that might contribute to the astrobiology field.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 8","pages":"824-838"},"PeriodicalIF":3.5,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142003500","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":"Biosignature Molecules Accumulate and Persist in Evaporitic Brines: Implications for Planetary Exploration.","authors":"Chad Pozarycki, Kenneth M Seaton, Emily C Vincent, Carlie Novak Sanders, Nickie Nuñez, Mariah Castillo, Ellery Ingall, Benjamin Klempay, Alexandra Pontefract, Luke A Fisher, Emily R Paris, Steffen Buessecker, Nikolas B Alansson, Christopher E Carr, Peter T Doran, Jeff S Bowman, Britney E Schmidt, Amanda M Stockton","doi":"10.1089/ast.2023.0122","DOIUrl":"https://doi.org/10.1089/ast.2023.0122","url":null,"abstract":"<p><p>The abundance of potentially habitable hypersaline environments in our solar system compels us to understand the impacts of high-salt matrices and brine dynamics on biosignature detection efforts. We identified and quantified organic compounds in brines from South Bay Salt Works (SBSW), where evapoconcentration of ocean water enables exploration of the impact of NaCl- and MgCl₂-dominated brines on the detection of potential biosignature molecules. In SBSW, organic biosignature abundance and distribution are likely influenced by evapoconcentration, osmolyte accumulation, and preservation effects. Bioluminescence assays show that adenosine triphosphate (ATP) concentrations are higher in NaCl-rich, low water activity (<i>a</i>_w) samples (<0.85) from SBSW. This is consistent with the accumulation and preservation of ATP at low <i>a</i>_w as described in past laboratory studies. The water-soluble small organic molecule inventory was determined by using microchip capillary electrophoresis paired with high-resolution mass spectrometry (µCE-HRMS). We analyzed the relative distribution of proteinogenic amino acids with a recently developed quantitative method using CE-separation and laser-induced fluorescence (LIF) detection of amino acids in hypersaline brines. Salinity trends for dissolved free amino acids were consistent with amino acid residue abundance determined from the proteome of the microbial community predicted from metagenomic data. This highlights a tangible connection up and down the \"-omics\" ladder across changing geochemical conditions. The detection of water-soluble organic compounds, specifically proteinogenic amino acids at high abundance (>7 mM) in concentrated brines, demonstrates that potential organic biomarkers accumulate at hypersaline sites and suggests the possibility of long-term preservation. The detection of such molecules in high abundance when using diverse analytical tools appropriate for spacecraft suggests that life detection within hypersaline environments, such as evaporates on Mars and the surface or subsurface brines of ocean world Europa, is plausible and argues such environments should be a high priority for future exploration. Key Words: Salts-Analytical chemistry-Amino acids-Biosignatures-Capillary electrophoresis-Preservation. Astrobiology 24, 795-812.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 8","pages":"795-812"},"PeriodicalIF":3.5,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142003497","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":"The Astrobiological Potential of the Uranian Moon System.","authors":"Jessica M Weber, Erin J Leonard","doi":"10.1089/ast.2024.0045","DOIUrl":"https://doi.org/10.1089/ast.2024.0045","url":null,"abstract":"<p><p>The 2023-2032 Planetary Science and Astrobiology Decadal Survey prioritized the Uranus Orbiter and Probe (UOP) mission concept as the next priority flagship mission. The UOP concept includes scientific studies of the Uranian moon system. Although the Uranian moons differ greatly from the ocean worlds in the Jovian and Saturnian systems, the emerging hypothesis is that some of them could at least sustain thin, potentially concentrated, oceans. Herein, we make a case that these moons are important and interesting targets of astrobiological research. Studying these worlds would provide critical astrobiological data related to their habitability, including origin, evolution, and potential death, as well as the formation and evolution of ocean worlds more broadly. There is a strong need for research that connects astrobiology to modeling and experimentation to better characterize the possible conditions of these worlds, and this will be critical in formulating and maximizing the potential science that could be done by a Uranus flagship mission.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 8","pages":"839-844"},"PeriodicalIF":3.5,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142003501","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":"A Bayesian Analysis of the Probability of the Origin of Life Per Site Conducive to Abiogenesis.","authors":"Manasvi Lingam, Ruth Nichols, Amedeo Balbi","doi":"10.1089/ast.2024.0037","DOIUrl":"https://doi.org/10.1089/ast.2024.0037","url":null,"abstract":"<p><p>The emergence of life from nonlife, or abiogenesis, remains a fundamental question in scientific inquiry. In this article, we investigate the probability of the origin of life (per conducive site) by leveraging insights from Earth's environments. If life originated endogenously on Earth, its existence is indeed endowed with informative value, although the interpretation of the attendant significance hinges critically upon prior assumptions. By adopting a Bayesian framework, for an agnostic prior, we establish a direct connection between the number of potential locations for abiogenesis on Earth and the probability of life's emergence per site. Our findings suggest that constraints on the availability of suitable environments for the origin(s) of life on Earth may offer valuable insights into the probability of abiogenesis and the frequency of life in the universe.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":"24 8","pages":"813-823"},"PeriodicalIF":3.5,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142003496","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}