Abstract Caves serve as terrestrial analogues for extraterrestrial subsurface environments: permanently dark, nutrient-poor and physicochemically stable on biologically relevant timescales. Morca Cave (Anamur, Mersin, Türkiye) extends to depths below 1200 m and is one of Türkiye’s deepest and least disturbed cave systems. Within our study, Gram-positive bacteria dominated at four of the five sampling sites (64.4–86.7%), while Gram-negative bacteria predominated at only one site (51.4%). Thirty-nine isolates produced visible yellow or orange pigmentation under laboratory conditions and were selected for further characterisation. Thin-layer chromatography detected xanthophyll-type pigments in 35 of these 39 isolates and a β-carotene-range spot in 22. HPLC tentatively identified a lutein-like xanthophyll in 36 of 39 isolates at concentrations of 1.34–34.65 ppb. Only two isolates yielded quantifiable HPLC peaks tentatively assigned to putative β-carotene; the remaining high-Rf TLC bands likely correspond to other apolar carotenoids. All pigment identifications are tentative, based on TLC and HPLC matching against authentic standards, and require LC-MS/MS or NMR confirmation. 16S rRNA gene sequencing assigned 31 of the 39 pigmented isolates to known taxa. Actinomycetia accounted for 20 isolates, Betaproteobacteria for six, Alphaproteobacteria for two, Bacilli for two and Gammaproteobacteria for one. Lutein-like pigment was recovered from bacteria isolated from surface samples at all three depths (−400, −620, −680 m) and from sediment samples at −400 and −620 m under standard heterotrophic cultivation; these isolates therefore retain biosynthetic capacity for carotenoid production independent of light. To our knowledge, this is the first study combining carotenoid profiling with 16S rRNA gene-based taxonomic assignment across a vertical depth gradient in a Turkish deep-karst cave system. The pigment concentration ranges and taxonomic distribution reported here provide an initial empirical reference dataset for carotenoid biosignature research in aphotic, oligotrophic subsurface environments proposed as terrestrial analogues for Mars and icy-moon habitability studies.
Abstract Mitigating the forward contamination of Mars in the vicinity of a landed spacecraft is a significant concern for future life-detection experiments. Here we model the dispersal of bacterial cells or spores (henceforth spores) from a single dispersal event at landing that injects 100 viable spores to a height of 100 m followed by settling of the spore plume under no-wind or windy scenarios. Subsequent to the single dispersal event, it is assumed that all spores remain viable during dispersal, during their residence time on the surface terrain and throughout the eventual collection of regolith or rock samples. The highest risk for recovering one viable spore after dispersal is in a circle with a radius of 10 m, under a no-wind scenario, and approaches a probability ( P ) of ≤ 1 × 10 −3 . If the spores are lofted with a wind at 1 m/s, the P values for recovering one spore range between 1 × 10 −5 at 20 m and 5 × 10 −8 at 500 m downwind, respectively. As the wind speeds increase to 10 m/s, the dispersal cones increase downwind to over 7000 m and their aspect ratio narrows significantly. At 10 m/s, P approaches ≤ 1 × 10 −9 for recovering one viable spore at 7000 m. If a rover is landed and the traverse is orthogonal to the downwind spore dispersal plume, P = 0, except where sampling vibrations of the rover arm might create secondary dispersal events. Results suggest that the risks of false positives in life-detection experiments from dispersed spores are very low.
The search for new bright scintillators with performance close to ideal is the target for many research centers worldwide. This paper presents advanced bright thallium (Tl)-based K2PtCl6-type intrinsic scintillators for detection and imaging applications. Dopant-free Tl-based compounds of Tl2HfX6 and Tl2ZrX6 (X = Cl, Br, or mixed halogens) that were investigated, grown, and published previously are now scaled up to one-inch-diameter crystals. Energy resolutions of 4.1% for Tl2HfCl6, 4.4% for Tl2ZrCl6, 4.8% for Tl2Hf(Cl,Br)(6), and 4.1% for Tl2Zr(Cl,Br)(6), as well as light yields of 22,300 ph/MeV for Tl2HfCl6, 38,500 ph/MeV for Tl2ZrCl6, 19,000 ph/MeV for Tl2Hf(Cl,Br)(6), and 39,900 ph/MeV for Tl2Zr(Cl,Br)(6), are measured. These crystals have generally linear responses to gamma-rays above 100 keV. Because of their many favorable attributes, these novel crystals will be beneficial in many gamma-ray detector applications that require better physical densities, Z(eff) values, energy resolutions, and relative detection efficiency than NaI:Tl, without the constraints of light yield and decay time constants.
Abstract The contested 2020 report of phosphine in Venus’s atmosphere triggered one of the most prominent recent debates in astrobiology, raising the possibility of extraterrestrial life while exposing deep scientific uncertainty. This study examines how English-language news media communicated this uncertainty over time and across news outlet types. Drawing on a standardized content analysis of news coverage published between September 2020 and June 2025, we trace shifts in uncertainty framing across four periods of the scientific debate. Findings show that media coverage was closely aligned to the scientific agenda. However, media reports – particularly during the initial discovery period – often expressed greater certainty about both phosphine and extraterrestrial life than was apparent in exemplary scientific publications. Consensus uncertainty was the most prominent uncertainty frame, accurately reflecting expert disagreement while posing potential challenges for public trust. Media types differed markedly, with mass-market media exhibiting more sensational framing and specialist science outlets adopting greater epistemic caution. Notably, clickbaiting strategies were relatively rare across the sample. Together, the findings show how media coverage selectively communicates and contextualizes uncertainty in reporting on frontier science.
FeII-doped zinc ferrite nanocrystals (FeII xZn1-xFeIII 2O4) were prepared via a sol-gel approach in the presence of polyvinyl alcohol as a stabilizer and assessed for their capability to eliminate crystal violet (CV) dye from water-based solutions. The structural and surface characteristics of the prepared materials were examined by XRD, HRTEM, FESEM, ATR-FTIR, XPS, UV-visible spectrophotometer and BET analyses. XRD patterns confirmed the formation of a cubic spinel ferrite structure (Fd-3m), indicating successful incorporation of FeII into the ZnFe2O4 lattice. ATR-FTIR spectra showed characteristic metal-oxygen vibrations at the tetrahedral and octahedral sites. XPS analysis confirmed the coexistence of FeII and FeIII species, which may promote interfacial charge transfer and redox reactions. HRTEM and FESEM images showed particle agglomeration and grain growth after calcination at 700 degrees C. FeII 0.2Zn0.8FeIII 2O4 exhibited the highest photocatalytic performance, achieving 97.2% degradation of CV under optimized conditions. The effects of contact time, catalyst dosage, initial dye concentration, and pH were systematically studied. The maximum removal efficiency was obtained at pH 10 using 0.075 g catalyst for 20 mg L-1 CV solution within 40 min. Freundlich isotherm models exhibited the strongest correlation (R2 = 0.918), pointing to multilayer adsorption occurring across a non-uniform nanoparticle surface. The Dubinin-Radushkevich analysis returned an adsorption energy of 3.01 kJ mol-1, implying that physical forces predominantly control the adsorption mechanism. Kinetic investigations revealed a two-stage CV uptake pathway: fast initial binding at exterior surface sites, succeeded by a slower migration of dye molecules into the internal pores of the adsorbent.
