Astrobiology最新文献

{"title":"Carbon and Sulfur Isotopes of Microfossils and Pyrites from Neoarchean Cherts: Microbial Diversity in an Ancient Deep-Marine Environment.","authors":"Jeffrey T Osterhout, Andrew D Czaja, Kenneth H Williford, Kouki Kitajima","doi":"10.1177/15311074261485886","DOIUrl":"https://doi.org/10.1177/15311074261485886","url":null,"abstract":"<p><p>The 2.52 Ga Gamohaan Formation in South Africa offers critical insights into microbial ecosystems that inhabited deep-marine environments during the late Archean. Large spheroidal microfossils and pyrite grains preserved in finely laminated black cherts reveal evidence of diverse metabolic processes and a complex deep-marine sulfur cycle. This study combines optical microscopy, scanning electron microscopy, and Raman spectroscopy to characterize fossil kerogen and sedimentary pyrites, along with secondary ion mass spectrometry to analyze their <i>in situ</i> carbon (δ¹³C) and sulfur (δ³⁴S) isotope compositions, respectively. Raman spectroscopy established the kerogenous composition and thermal maturity of the microfossils. <i>In situ</i> δ¹³C_org values (-41.3‰ to -32.2‰) are lower on average than bulk organic matter and define two statistically distinct δ¹³C_org populations, with large spheroidal fossils exhibiting systematically lower values than small spheroids. This size-correlated pattern is consistent with differences in carbon sources, fixation pathways, or ecological setting. Secondary ion mass spectrometry δ³⁴S analyses of pyrite grains (-0.7‰ to +6.3‰) show variability corresponding to differences among pyrite morphologies, consistent with microbial sulfate reduction and further sulfur cycling under sulfate-limited conditions in this deep-marine environment. These isotope data provide an independent geochemical framework for evaluating sulfur-based chemotrophic interpretations of the microfossil assemblage. Collectively, the carbon and sulfur isotope signatures support the presence of a complex benthic sulfur cycle and highlight the ecological and metabolic complexity of offshore marine ecosystems in the Neoarchean.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261485886"},"PeriodicalIF":2.3,"publicationDate":"2026-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148890809","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":"Habitability and Biosignatures on Earth and Mars.","authors":"Jeffrey T Osterhout, Jonathan Lima-Zaloumis, Ashley Manning-Berg, Marisol Juarez Rivera, Andrea Corpolongo-Smith","doi":"10.1177/15311074261485884","DOIUrl":"https://doi.org/10.1177/15311074261485884","url":null,"abstract":"","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261485884"},"PeriodicalIF":2.3,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148872943","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":"UV Exposure Study of 1-Methylnicotinamide Chloride: Self-Preservation in a Simple NAD(P)⁺ Analog.","authors":"Alexander Engel, Henry Strasdeit, Stefan Fox, Ronny Löffler","doi":"10.1177/15311074261483400","DOIUrl":"https://doi.org/10.1177/15311074261483400","url":null,"abstract":"<p><p>Chemical biosignatures, if present, are exposed to ultraviolet (UV) radiation at several locations in the solar system, including the Martian surface. Solid thin-layer samples are commonly used to study the effect of UV irradiation on the stability of potential organic biosignatures in the laboratory and in space. Given the limitations of the layer deposition techniques previously used in astrobiology experiments, such as sublimation-recondensation and casting, antisolvent precipitation (<i>i.e.</i>, crystallization from solution by addition of a poor solvent) offers a promising alternative. We applied the latter technique to deposit optically opaque crystalline layers of 1-methylnicotinamide chloride ((MNA)Cl) for use in subsequent UV irradiation experiments. The 1-methylnicotinamide cation in (MNA)Cl serves as a model of hypothetical extraterrestrial nicotinamide-based redox cofactors related to NAD(P)⁺. Under UV irradiation (<i>λ</i> ≥ 224 nm), decomposition of (MNA)Cl occurred, but it ceased after ∼14 days, leaving a large fraction of the material intact. This behavior is attributed to the shielding effect of a photoproduct layer on the crystal surfaces and can be kinetically described by a first-order bounded decay model. Such \"self-preservation\" may enhance the survivability of certain organic biosignatures provided they form sufficiently thick (opaque) layers or crystals. The presence of either synthetic gypsum (CaSO₄·2H₂O) or halite (NaCl) had a minimal effect on the kinetic parameters of the UV decomposition of (MNA)Cl.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261483400"},"PeriodicalIF":2.3,"publicationDate":"2026-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148863504","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":"Multi-Excitation Raman Spectroscopy of Carbonaceous Matter within Opaline Silica Sinters from Mars-Analog Hot Spring Settings: Implications for the Search for Extraterrestrial Biosignatures.","authors":"Rui-Lin Cheng, Carolina Munoz-Saez, Kathleen A Campbell, Joseph R Michalski, Andrew D Czaja, Steven W Ruff","doi":"10.1177/15311074261483387","DOIUrl":"https://doi.org/10.1177/15311074261483387","url":null,"abstract":"<p><p>Silica sinters are promising astrobiology targets in the search for signs of past extraterrestrial life on Mars. Although terrestrial sinter morphologic features may serve as potential biosignatures at the macroscale, identification of carbonaceous matter (CM) within silica would offer substantial support for interpreting martian silica deposits as having a biologic association. Raman spectroscopy provides a means to identify both minerals and organics <i>in situ</i>. This technique has been employed to analyze CM in terrestrial sinters that consist of microcrystalline quartz and has also been deployed previously on the mars to search for organics. However, martian silica deposits are dominated by opaline silica rather than quartz, and a thorough examination of CM within terrestrial opaline silica by Raman spectroscopy is generally lacking. We investigated opaline silica sinters from northern Chile, an exceptional terrestrial analog for Mars, by Raman spectroscopy with multiple excitations. Our results show that strong fluorescence from opaline silica modifies CM Raman spectral signatures across excitation wavelengths. CM Raman spectra within opaline silica sinters vary both among facies and within individual samples, and they differ from those in Archean cherts. This study demonstrates that reliable interpretation of CM Raman spectra requires attention to host-matrix influences, excitation wavelength, and curve-fitting procedures.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261483387"},"PeriodicalIF":2.3,"publicationDate":"2026-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148863557","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":"Diversity Lost in Space: Discrimination and Exclusion in Astrobiology.","authors":"Arsev Umur Aydinoglu, Ozgur Kadir Ozer","doi":"10.1177/15311074261483886","DOIUrl":"https://doi.org/10.1177/15311074261483886","url":null,"abstract":"<p><p>This study presents an analysis of diversity, equity, and inclusion in the U.S. astrobiology community. Using national survey data, we examined how gender, race, age, and career stage affect researchers' experiences with mentorship, funding, and career advancement. The results reveal disparities: female participants reported gender discrimination at seven times the rate of male respondents, and 85% of all respondents had encountered harassment. Nearly half experienced career interruptions, most commonly due to mental health challenges (57%), family obligations, or harassment. Other persistent barriers included difficulty meeting workplace expectations (84%), securing permanent positions (40%), and obtaining adequate funding (nearly one-third). Female researchers reported lower levels of workplace support and collegial respect than their male peers. While some institutions have begun implementing equity-focused practices, adoption across the field remains limited. Based on these findings, we recommend that institutions publicly report diversity metrics, establish targeted mentorship programs, and provide mental health support and parental leave policies. Addressing these systemic barriers is essential not only for ethical reasons but also for advancing astrobiology's mission, which depends on diverse perspectives and collaboration.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261483886"},"PeriodicalIF":2.3,"publicationDate":"2026-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148863514","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":"Signatures of Silicification in Lava Tubes: Implications for Biosignature Preservation and Detection on Earth and Mars.","authors":"Dina M Bower, Maëva Millan, Mathilde Musetta, Clara Christiann, Amy C McAdam, Christine A Knudson, Jamielyn Jarvis, Cherie N Achilles, Jacob Richardson, Patrick L Whelley, Conor A Nixon, Mary N Parenteau","doi":"10.1177/15311074261484811","DOIUrl":"https://doi.org/10.1177/15311074261484811","url":null,"abstract":"<p><p>Terrestrial lava tubes serve as analogs for potentially habitable subsurface environments on Mars due to the bioenergetic potential of basalts, formation of secondary minerals, presence of actively seeping fluids, and isolation from the surface. On Earth, a wide variety of microbial communities that thrive in lava tubes often leave behind detectable traces of their presence and activity. To further an understanding of the contribution that secondary minerals, such as amorphous silica, can make to the preservation of organic material in lava tubes, we analyzed a small set of silica-rich basaltic lava tube samples from Mauna Loa, Hawai'i, and Lava Beds National Monument, CA. We applied techniques relevant to current Mars missions (Raman spectroscopy, powder X-ray diffractometry, gas chromatograph-mass spectrometry, scanning electron microscopy, and energy-dispersive X-ray spectrometry) and compared our datasets with those collected previously from similar analyses of siliceous sinter deposits from Yellowstone National Park. Despite variations in major elemental and organic compositions, distributions, and concentrations, we did not observe differences in the Raman spectroscopy and X-ray diffractometer data of the different silica-rich samples. Organic molecules were detected by Raman spectroscopy in all samples with varying degrees of specificity, regardless of the presence of morphological evidence of microbes or apparent degree of silicification. Pyrolysis and thermochemolysis gas chromatograph-mass spectrometry analysis also revealed the presence of numerous organic fragments that were likely derived from the remains of microbial communities in the lava tube samples. Where microbial material was observed, there were often overlapping spectra in some of the biomolecular and amorphous silica Raman signatures, which required careful interpretation that included scanning electron microscopy and gas chromatograph-mass spectrometry. Our data indicate that amorphous silica formation in lava tubes can obscure over time the distinctive morphological characteristics of microbial remains, though the chemical signatures of biomolecular compounds can still be detectable. Our findings have implications for the types of instrument packages that could be selected to assess the chemical makeup and textures of silica-rich lava tube deposits and suggest that more targeted studies are warranted to understand the possible implications for biosignature preservation and detection in such environments.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261484811"},"PeriodicalIF":2.3,"publicationDate":"2026-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148863532","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 Model of UV-Blue Absorbance in Bulk Liquid of Venusian Cloud Aerosols Is Consistent with Efficient Organic Absorbers at High Concentrations.","authors":"Jan Spacek, Paul B Rimmer, Janusz J Petkowski, Yeon Joo Lee","doi":"10.1177/15311074261477502","DOIUrl":"10.1177/15311074261477502","url":null,"abstract":"<p><p>At visible wavelengths, Venus appears serene and pale yellow. But since the 1920s, observers have noted high-contrast features in the ultraviolet. These features track the ∼4-day superrotation of the upper cloud deck and vary widely over time and space. The identity of the UV absorber(s)-active between at least 280 and 500 nm-remains unknown, as no proposed candidate fully matches all observational data. From remote observations of Venus, and accounting for light scattering by cloud droplets, we modeled the 365-455 nm decadic absorption coefficient, <math><mrow><mrow><msub><mrow><mi>a</mi></mrow><mi>λ</mi></msub></mrow></mrow></math>, of the bulk liquid that forms Venus's clouds. Assuming a uniform distribution in mode 1 and mode 2 particles across a 6 km layer below the cloud top at 65 km, we constrained the decadic absorption coefficient within the modeled range to a peak at <math><mrow><mrow><msub><mrow><mi>a</mi></mrow><mrow><mn>375</mn></mrow></msub></mrow></mrow></math> = 1278 cm^-1, equivalent to a decadic absorbance of <math><mrow><mrow><msub><mrow><mi>A</mi></mrow><mrow><mn>375</mn></mrow></msub></mrow></mrow></math> = 1278 for a 1 cm path length. This extremely high absorption coefficient implies the presence of a highly efficient absorber, for example, conjugated organics, at relatively high concentrations-for example, ∼12 g/L for porphyrin-type pigments with a representative peak molar absorption coefficient of ∼10⁵ M^-1cm^-1. Inorganic absorbers, typically below 10⁴ M^-1cm^-1, would either need to constitute a large portion of the aerosols or still not be sufficiently light-absorbing, even in pure form. We emphasize that all candidate absorbers must be evaluated against Venus's reflectance curve using (1) known molar absorption coefficients, (2) realistic atmospheric distributions, and (3) appropriate particle size distributions. The planned Rocket Lab mission will test the hypothesis of organics in Venus's clouds.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261477502"},"PeriodicalIF":2.3,"publicationDate":"2026-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148811951","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":"Assessing the Climate and Habitability of Tidally Locked Rocky Exoplanets.","authors":"Erica Bisesi, Giuseppe Murante, Jost von Hardenberg, José A Caballero, Michele Maris, Daniela Billi, Nicoletta La Rocca, Laura Silva","doi":"10.1177/15311074261479167","DOIUrl":"https://doi.org/10.1177/15311074261479167","url":null,"abstract":"<p><p>Tidally locked exoplanets orbiting M dwarf stars are prime targets in the search for habitable worlds, yet their complex climate dynamics challenge conventional models of habitability. We homogeneously estimated the liquid-water habitability of exoplanets with the highest up-to-date Earth similarity index (ESI). We modified the climate model PLASIM to apply it to tidally locked exoplanets across a range of parameters. We systematically classified and compared potentially habitable exoplanets and selected among the ones featuring the highest ESI in the conservative sample of the Habitable Worlds Catalog, both relative to each other and as a function of atmospheric pressure. Our analysis revealed three main climate regimes: Snowball, Hot, and Eyeball planets-the latter having a warm and habitable substellar region with <i>T</i> > 273 K and a localized hydrological cycle. Although surface temperature generally increases with pressure, Eyeball planet climates remain stable in a wide pressure range. Complex atmospheric dynamics rules the behavior of the climate, highlighting the need for detailed climate simulations to guide future observations.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261479167"},"PeriodicalIF":2.3,"publicationDate":"2026-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148787457","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":"Wavelength Requirements for Life Detection via Reflected Light Spectroscopy of Rocky Exoplanets.","authors":"Joshua Krissansen-Totton, Anna Grace Ulses, Maxwell K Frissell, Samantha Gilbert-Janizek, Amber Young, Jacob Lustig-Yaeger, Tyler D Robinson, Stephanie Olson, Eleonora Alei, Giada Arney, Celeste Hagee, Chester Harman, Natalie Hinkel, Émilie Laflèche, Natasha Latouf, Avi Mandell, Mark M Moussa, Mary N Parenteau, Sukrit Ranjan, Blair Russell, Edward W Schwieterman, Clara Sousa-Silva, Armen Tokadjian, Nicholas Wogan","doi":"10.1177/15311074261477497","DOIUrl":"https://doi.org/10.1177/15311074261477497","url":null,"abstract":"<p><p>Searching for signs of life is a primary goal of the Habitable Worlds Observatory (HWO). However, merely detecting oxygen, methane, or other widely discussed biosignatures is insufficient evidence for a biosphere. In parallel with biosignature detection, exoplanet life detection additionally requires characterization of the broader physicochemical context to evaluate planetary habitability and the plausibility that life could produce a particular biosignature in a given environment. Life detection further requires that we can confidently rule out photochemical or geological phenomena that can mimic life (i.e., \"false positives\"). Evaluating false-positive scenarios may require different observatory specifications than biosignature detection surveys. Here, we explore the coronagraph requirements for assessing habitability and for cautiously excluding known false-positive (and false-negative) scenarios for oxygen and methane, the two most widely discussed biosignatures for Earth-like exoplanets. We find that broad wavelength coverage ranging from the near ultraviolet (UV; 0.26 µm) and extending into the near infrared (NIR; 1.7 µm) is necessary to contextualize these potential biosignatures with HWO. The short-wavelength cutoff is driven by the need to identify Proterozoic-like biospheres via O₃, whereas the long-wavelength cutoff is driven by the need to contextualize O₂ and CH₄ biosignatures via constraints on carbon-bearing atmospheric species. The ability to obtain spectra with signal-to-noise ratios of 20-40 across this 0.26-1.7 µm range (assuming R = 7 UV, R = 140 VIS, and R = 70 NIR) is also required. While not every Earth-analog biosignature and false positive can be unambiguously identified with these capabilities-and the plausibility and contextual clues of many biosignature false positives remain an area of active research-our minimal spectral recommendations would enable a broad search for Earth-like life assuming such observations are achievable for a statistically meaningful number of HWO targets.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261477497"},"PeriodicalIF":2.3,"publicationDate":"2026-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148757669","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":"Reactive Iron Mineral Phases on Mars: Implications for Organic Carbon Preservation.","authors":"Emily Bonsall, Eileen Tisdall, Christian Schröder","doi":"10.1177/15311074261475984","DOIUrl":"https://doi.org/10.1177/15311074261475984","url":null,"abstract":"<p><p>It is estimated that ∼20% of organic carbon stored in sediments on Earth is bound to reactive iron minerals. They often occur as nanoparticulate or X-ray amorphous iron (hydr)oxides, which are challenging to identify with mineralogical techniques-especially those that require any type of heating, which also makes them susceptible to alteration in response to diagenetic processes. Reactive iron species have been identified on Mars in the form of nanophase ferric oxides in Gusev crater and at Meridiani Planum with Spirit's and Opportunity's Mössbauer spectrometers, respectively, and as Fe-rich amorphous material in Gale crater with Curiosity's CheMin X-ray diffraction channel. Here, we use the amount of reactive iron minerals and geochemical evidence for diagenetic processes to assess the relative preservation potential of sedimentary rocks at these three landing sites. Sedimentary rocks in Gale crater show the highest preservation potential, and organic carbon compounds have been identified in these rocks. Sedimentary rocks in Gusev crater show equally high preservation potential. However, reactive Fe minerals can also react with organic carbon when heat is added during pyrolysis and laser desorption. These effects need to be considered to determine accurately the organic carbon inventory measured during current and future missions as well as in returned samples.</p>","PeriodicalId":8645,"journal":{"name":"Astrobiology","volume":" ","pages":"15311074261475984"},"PeriodicalIF":2.3,"publicationDate":"2026-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148757949","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}