Enough Sulfur and Iron for Potential Life Make Enceladus’s Ocean Fully Habitable
The Cassini spacecraft revealed life-forming elements like CHNOP and diverse organic compounds from Enceladus’s ocean. However, the availability of minor but bio-essential nutrients such as iron and sulfur remains unknown. Here, we perform geochemical modeling to explore their chemistry in Enceladus...
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| Language: | English |
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2025-01-01
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| Series: | The Astrophysical Journal Letters |
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| Online Access: | https://doi.org/10.3847/2041-8213/adad65 |
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| author | Weiming Xu Can Liu Ao Zhang Maggie Lau H. James Cleaves Fang Huang Christopher R. Glein Jihua Hao |
| author_facet | Weiming Xu Can Liu Ao Zhang Maggie Lau H. James Cleaves Fang Huang Christopher R. Glein Jihua Hao |
| author_sort | Weiming Xu |
| collection | DOAJ |
| description | The Cassini spacecraft revealed life-forming elements like CHNOP and diverse organic compounds from Enceladus’s ocean. However, the availability of minor but bio-essential nutrients such as iron and sulfur remains unknown. Here, we perform geochemical modeling to explore their chemistry in Enceladus’s ocean. We find that dissolved iron predominantly occurs as Fe( ii ) with a solubility ranging from 10 ^−8 to 10 ^−5 mole (kg H _2 O) ^−1 (decreasing with increasing pH). Dissolved sulfur, mainly present as HS ^− , is predicted to have a concentration of 10 ^−6 to 10 ^−4 mole (kg H _2 O) ^−1 , and pH has only a minor effect on S solubility. Our predicted availabilities of Fe and S are close to measured concentrations in inhabited terrestrial serpentinization fluids, implying sufficient nutrients to support potential life. Our results also suggest that the reduction of ferric iron or sulfate might supply enough energy for chemotrophic metabolisms based on these reactions to complement previously proposed methanogenesis. The levels of bioproductivity supported by S availability are overall lower than those sustained by other nutrients, but still orders of magnitude higher than the maximum level of bioproductivity estimated from the supply of chemical energy. |
| format | Article |
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| institution | Kabale University |
| issn | 2041-8205 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal Letters |
| spelling | doaj-art-78cdec92f8b2494cb822bccd09f5dc912025-02-07T07:17:03ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019801L1010.3847/2041-8213/adad65Enough Sulfur and Iron for Potential Life Make Enceladus’s Ocean Fully HabitableWeiming Xu0https://orcid.org/0009-0007-3010-6809Can Liu1https://orcid.org/0009-0006-8036-0509Ao Zhang2Maggie Lau3H. James Cleaves4https://orcid.org/0000-0003-4101-0654Fang Huang5Christopher R. Glein6https://orcid.org/0000-0002-2161-4672Jihua Hao7https://orcid.org/0000-0003-3657-050XNational Key Laboratory of Deep Space Exploration, Deep Space Exploration Laboratory, State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China , Hefei 230026, People’s Republic of China ; hao@ustc.edu.cnNational Key Laboratory of Deep Space Exploration, Deep Space Exploration Laboratory, State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China , Hefei 230026, People’s Republic of China ; hao@ustc.edu.cnNational Key Laboratory of Deep Space Exploration, Deep Space Exploration Laboratory, State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China , Hefei 230026, People’s Republic of China ; hao@ustc.edu.cnLaboratory of Extraterrestrial Ocean Systems, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences , Sanya, Hainan 572000, People’s Republic of ChinaEarth and Planets Laboratory, Carnegie Institution for Science , Washington, DC 20015, USA; Department of Chemistry, Howard University , Washington, DC 20059, USA; Blue Marble Space Institute for Science , Seattle, WA 98104, USANational Key Laboratory of Deep Space Exploration, Deep Space Exploration Laboratory, State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China , Hefei 230026, People’s Republic of China ; hao@ustc.edu.cn; CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China , Hefei 230026, People’s Republic of ChinaSpace Science Division, Southwest Research Institute , San Antonio, TX 78238, USA ; christopher.glein@swri.orgNational Key Laboratory of Deep Space Exploration, Deep Space Exploration Laboratory, State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China , Hefei 230026, People’s Republic of China ; hao@ustc.edu.cn; CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China , Hefei 230026, People’s Republic of ChinaThe Cassini spacecraft revealed life-forming elements like CHNOP and diverse organic compounds from Enceladus’s ocean. However, the availability of minor but bio-essential nutrients such as iron and sulfur remains unknown. Here, we perform geochemical modeling to explore their chemistry in Enceladus’s ocean. We find that dissolved iron predominantly occurs as Fe( ii ) with a solubility ranging from 10 ^−8 to 10 ^−5 mole (kg H _2 O) ^−1 (decreasing with increasing pH). Dissolved sulfur, mainly present as HS ^− , is predicted to have a concentration of 10 ^−6 to 10 ^−4 mole (kg H _2 O) ^−1 , and pH has only a minor effect on S solubility. Our predicted availabilities of Fe and S are close to measured concentrations in inhabited terrestrial serpentinization fluids, implying sufficient nutrients to support potential life. Our results also suggest that the reduction of ferric iron or sulfate might supply enough energy for chemotrophic metabolisms based on these reactions to complement previously proposed methanogenesis. The levels of bioproductivity supported by S availability are overall lower than those sustained by other nutrients, but still orders of magnitude higher than the maximum level of bioproductivity estimated from the supply of chemical energy.https://doi.org/10.3847/2041-8213/adad65EnceladusSaturnian satellitesAstrobiology |
| spellingShingle | Weiming Xu Can Liu Ao Zhang Maggie Lau H. James Cleaves Fang Huang Christopher R. Glein Jihua Hao Enough Sulfur and Iron for Potential Life Make Enceladus’s Ocean Fully Habitable The Astrophysical Journal Letters Enceladus Saturnian satellites Astrobiology |
| title | Enough Sulfur and Iron for Potential Life Make Enceladus’s Ocean Fully Habitable |
| title_full | Enough Sulfur and Iron for Potential Life Make Enceladus’s Ocean Fully Habitable |
| title_fullStr | Enough Sulfur and Iron for Potential Life Make Enceladus’s Ocean Fully Habitable |
| title_full_unstemmed | Enough Sulfur and Iron for Potential Life Make Enceladus’s Ocean Fully Habitable |
| title_short | Enough Sulfur and Iron for Potential Life Make Enceladus’s Ocean Fully Habitable |
| title_sort | enough sulfur and iron for potential life make enceladus s ocean fully habitable |
| topic | Enceladus Saturnian satellites Astrobiology |
| url | https://doi.org/10.3847/2041-8213/adad65 |
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