Blue Marble Space

The characterization and identification of possible cryovolcanic activity on Ganymede is key to understanding the evolution and potential habitability of Jupiter’s largest moon. ESA’s JUpiter ICy moons Explorer (JUICE) mission, launched in 2023, will provide the first dedicated, high-resolution investigation of Ganymede’s surface and interior. Before JUICE reaches Jupiter’s system and obtains its first observations of Ganymede, it is essential to reassess previously proposed cryovolcanic regions using a consistent and comparative approach.Based on Voyager and Galileo spectro-imaging, 20 paterae and morphologically distinctive features have been suggested as candidate cryovolcanic regions, yet their geological context and compositional diversity have not been systematically evaluated. In this work, we present a reanalysis of all candidate regions, combining regional geomorphological assessment with comparative near-infrared spectra. Reprocessed Galileo Near-Infrared Mapping Spectrometer (NIMS) data are examined using a uniform linear spectral unmixing framework, with emphasis on relative spectral trends and temperature-dependent behaviour rather than absolute compositional determinations.This data reprocessing and spectral comparisons reveal distinct spectral categories among candidate regions, ranging from ice-dominated terrains to areas exhibiting enhanced non-ice components. When combined with morphological characteristics that are often similar to confirmed cryovolcanic features on other planetary bodies, these groupings suggest that multiple formation and modification processes may be represented, including end-member cases consistent with cryovolcanic resurfacing or brine-related processes.Rather than providing definitive interpretations, this work establishes a pre-JUICE framework for target prioritization and observation planning. We discuss implications for high-resolution imaging and spectroscopy by the JANUS and MAJIS instruments, and how forthcoming JUICE data can discriminate between plausible geological scenarios.

Abstract Clouds are the largest source of uncertainty in climate simulations. For exoplanets, cloud simulation is particularly challenging because of the lack of observational data to tune parameterized cloud models. Here we apply Community Aerosol and Radiation Model for Atmospheres ( CARMA ), a size-resolved bin cloud microphysics model, to the atmospheric global climate model Community Atmosphere Model (CAM6) and simulate exoplanets with a range of planetary rotation rates. CARMA produces fewer liquid clouds than the native CAM6 parameterized cloud microphysics scheme (Morrison–Gettelman two-moment microphysics, MG), more ice clouds, and a significantly different ice cloud size distribution. Overall, this leads to a decrease in the magnitude of the net CRE by 4–10 W m −2 , which is unlikely to change the determination of habitability from a climate perspective in most cases. The difference in ice cloud size distribution is likely to strongly affect transmission spectral retrievals. Our work confirms that the MG parameterized cloud microphysics scheme can produce reasonable climate simulation when extrapolated to some exoplanet contexts and highlights the value of resolved cloud microphysics for evaluating parameterized schemes and for interpreting observations.

Abstract Doublet fluorescence at 304 and 325‐nm under deep ultraviolet (DUV) excitation was detected on Mars at Jezero crater by the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument onboard the Mars 2020 rover Perseverance . The doublet was associated with CaSO 4 phases and sourced to organic molecules as the preferred interpretation (Sharma et al., 2023, https://doi.org/10.1038/s41586‐023‐06143‐z ). Reported here are coordinated analyses of terrestrial volcanogenic samples that have, under DUV excitation, intrinsic 304 and 325‐nm fluorescence whose origin is tightly sourced to anhydrite:Ce 3+ (trace‐Ce 3+ for Ca 2+ substitution in natural anhydrous CaSO 4 ). Thermal decomposition products of natural volcanogenic gypsum (CaSO 4 ·2H 2 O) and sedimentary glauberite (Na 2 Ca(SO 4 ) 2 ) by aerial heating at more than 450°C and more than 600°C, respectively, are also characterized by 304 and 325‐nm fluorescence doublets that are sourced from anhydrite:Ce 3+ thermal decomposition products. The 304 and 325‐nm doublet fluorescence detected by SHERLOC is fully explainable by inorganic anhydrite:Ce 3+ resulting from geogenic processes. The volcanogenic samples are products of leaching and precipitation in hydrothermal environments. Leachates can precipitate in many ways, including intimate or proximal contact with residues and, after aqueous transport, as vein precipitate, fracture fill, and evaporite deposits. Equivalent considerations extend to hydrothermalism driven by impact melts and other thermal sources. Laboratory thermal decomposition of progenitor phases to anhydrite:Ce 3+ is an analogous process for contact and burial metamorphism. The coordinated analysis approach additionally includes major element and REE abundances (X‐ray fluorescence and inductive coupled plasma—mass spectrometry), X‐ray diffraction, DUV Raman spectroscopy, and thermal analysis (thermal gravimetry, differential scanning calorimetry, and evolved gas analysis).

Abstract Aminoacyl-tRNA synthetases are the guardians of translational fidelity. Their complex function is mirrored by an elaborate structure, which includes multiple nested domains. While the evolutionary pressures that promoted the emergence of some domains, such as the editing domain, are clear, the pressures acting on other domains, particularly those at the C-terminus, are not. Here, we use a combination of kinetic analysis, X-ray crystallography, and bioinformatics to unveil the history and evolutionary forces that have shaped isoleucyl-tRNA synthetase (IleRS) domain structure. We find that the traditional classification into IleRS1 and IleRS2, based on the C-terminal tRNA-recognition domains, is incomplete, as it fails to capture features of the synthetic domain. Guided by the crystal structure of the Priestia megaterium IleRS2:tRNA complex, we removed key interactions between IleRS2 and its cognate tRNA and characterised their impact on enzyme activity. We found that D-loop interactions with the IleRS2 C-terminal region are non-essential in prokaryotes, and their loss can even increase catalytic turnover. Further, the zinc-binding domain of IleRS1 recognises the anticodon less stringently than the canonical C-terminal domain of IleRS2. Our data suggest that C-terminal evolutionary remodelling of IleRSs is an ongoing process with a historical precedent, consistent with selection for faster aminoacylation rate.

Ocean memory embraces the idea that the ocean retains, processes, and expresses information across a range of timescales, from moments to millennia. The Ocean Memory Project brings together scientists, artists, and scholars to investigate this notion from a transdisciplinary perspective, integrating empirical research with creative expression. Here, our scientific and artistic efforts center on the Lost City hydrothermal field, an otherworldly site on the deep Atlantic seafloor that offers rare insights into early Earth processes and the potential for life beyond our planet. In 2018, we sailed to Lost City and carried out our joint microbiological, geochemical, and artistic efforts. Our sampling revealed that the ultramafic rocks that underlie the field undergo reactions that support complex ecosystems dependent on interspecies cooperation to overcome extreme chemical limitations. These same rocks serve as a geologic sink for organic carbon carried with circulating seawater, a process likely active for as long as hydrothermal circulation has existed on Earth. These discoveries highlight the complex, evolving nature of subseafloor ecosystems and exemplify the ocean’s capacity for memory. Alongside the science, the expedition supported an artist in residence, Anna Davidson, who created a body of work inspired by her time at sea. Her paintings, videos, photos, and mixed media sculptures, some incorporating physical samples and imagery from the dive footage, are not only aesthetic and conceptual reflections of Lost City but also educational resources. By integrating science and art, we argue in this paper for a broader epistemological framework in environmental research—one that recognizes the ocean not only as a site of data but as a dynamic, living archive of memories. Through interdisciplinary inquiry, we can deepen our understanding of the ocean and build more meaningful cultural narratives around its protection in the face of current mounting threats, including climate change and deep-sea mining.

Spaceflight studies present novel insights into biological processes through exposure to stressors outside the evolutionary path of terrestrial organisms. Despite limited access to space environments, numerous transcriptomic datasets from spaceflight experiments are now available through NASA’s GeneLab data repository, which allows public access, encouraging further analysis. While various computational pipelines and methods have been used to process these transcriptomic datasets, learning-model-driven analyses have yet to be applied to a broad array of such spaceflight-related datasets. In this study, we present an open-source pipeline, GLARE: GeneLAb Representation learning pipelinE, which consists of training different representation learning approaches from manifold learning to self-supervised learning that enhance the performance of downstream analytical tasks. We illustrate the utility of GLARE by applying it to gene-level transcriptional values from the results of the CARA spaceflight experiment, an Arabidopsis root tip transcriptome dataset that spanned light, dark, and microgravity treatments. We show that GLARE not only substantiated the findings of the original study concerning cell wall remodeling but also revealed additional patterns of gene expression affected by the treatments, including evidence of hypoxic response. This work suggests there is great potential to supplement the insights drawn from initial studies on spaceflight omics-level data through further machine-learning-enabled analyses.

Tokenization, a core concept in natural language processing, segments sequences into discrete, repetitive informational units. Here, we fit tokenizers to genomic data from a broad range of organisms to investigate how biological information is structured and compressed. We show that tokenization consistently outperforms standard compression algorithms, particularly for coding sequences. Compression improves with sequence length and varies systematically across taxonomic kingdoms. Token frequency patterns also reflect biological relationships, especially among eukaryotes. These findings suggest that tokenization offers a powerful framework for exploring how information is encoded in living systems.

Sulfate minerals are significant components of the martian surface and provide clues about the martian geochemical environment. One unusual Fe-sulfate phase has been intriguing Mars scientists for over a decade due to its unique spectral bands that are distinct from any known minerals and its occurrence in layered sedimentary rocks. We describe here detection of ferric hydroxysulfate (Fe3+SO4OH) and its implications for the geochemical history of Mars. Crystalline ferric hydroxysulfate is formed by heating hydrous Fe2+ sulfates to 100 °C or above and has a strong spectral band at 2.236 µm, similar to the spectral feature observed on Mars at Aram Chaos and on the plateau above Juventae Chasma. Hydrated sulfates at these locations likely formed through evaporative processes or low-temperature alteration. In contrast, Fe3+SO4OH is more consistent with heating and oxidation of hydrated ferrous sulfates, potentially through deposition of lava, ash, or through hydrothermal processes.

Keto-enol tautomerism plays a very important role in pyruvate chemistry and metabolic transformations. The enol form of pyruvate is thermodynamically much less stable, and its tautomerization to the keto form is one of the strongly favored energetic single rearrangements, endowing phosphoenolpyruvate as one of the most potent phosphate donors in biology. In this work, we report the keto-enol rearrangement of pyruvate and pyruvate-derived compounds, such as zymomate, using high-quality density functional theory for the gas phase and molecular dynamics methods for the aqueous phase. Our results indicate a preference for the keto tautomer of pyruvic acid and pyruvate both in the gas as well as in the aqueous phase. Zymonic acid prefers to be in the enol form in gas as well as in an aqueous medium. Tautomerization contributes approximately 42% of the energetic driving force in the hydrolysis of phosphenol pyruvate. Keto tautomer of zymonate, however, is lower in energy in the gas phase, while the enol tautomer, due to its strong solvation free energy, is lower in energy in the aqueous phase. The results of our work are also discussed in the context of astrobiology, where we explore how fundamental carbonyl chemistry such as keto-enol tautomerization reactions may have influenced the selection of phosphoenolpyruvate. We propose a scenario for how the emergence of PEP might have taken place through a process of chemical evolution originating from a wider variety of possible enol phosphates operating within a proto-metabolism.