Astrobiology最新文献

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.e., 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 (λ ≥ 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.

The transition to sustained human space exploration is reshaping how astrobiology can be conducted. As missions extend beyond low Earth orbit and involve governmental and commercial actors, astrobiology is increasingly becoming embedded in complex operational and policy environments. These developments can be seen as a shift in the operational, interpretive, and governance contexts of astrobiology, affecting how investigations are conducted, how findings are interpreted, and how research is coordinated across mission phases. Here, we outline the implications of human presence for astrobiology research and its integration within evolving exploration architectures, and examine its role in future missions.

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 in situ. This technique has been employed to analyze CM in terrestrial sinters that consist of microcrystalline quartz and has also been deployed previously on 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.

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.

The "Exploring the Abiotic Background for Life Detection" workshop was convened between March 31, 2025, and April 3, 2025, at the Carnegie Institution for Science in Washington, D.C. The workshop gathered scientists and technologists from different disciplines and career stages to consider the "abiotic background": recognizing, characterizing, and understanding the set of abiotic substances, structures, and processes that may result in potential false-positive or false-negative results in the search for evidence of life beyond Earth. To frame the conversation and ensure programmatic relevance, the workshop emphasized Ocean Worlds, while also leveraging lessons learned from modern and early Earth and Mars. Salient takeaways include the following: (1) a large abiotic background, potentially sustained over geologic timescales, could mimic, obscure, and alter biosignatures, posing risks of false positives and false negatives. Addressing these challenges requires balancing targeted and untargeted measurements within the constraints of robotic spacecraft payloads; (2) the search for signatures of life beyond Earth represents a sharp inflection point in spacecraft mission complexity and design. Stakeholders of such missions must strike a difficult balance between scientific aspirations and the technological constraints inherent to robotic spaceflight; (3) Ocean Worlds are a distinct class of habitable environments, each with unique evolutionary pathways, but collectively offering new opportunities to study organic chemical evolution; (4) there is a need to establish community-wide experimental standards and laboratory simulations to better constrain the range of abiotic chemistry and improve abiotic chemistry models to guide the design of spacecraft missions; (5) a unifying, predictive framework for abiotic chemical evolution could provide a robust baseline for interpreting mission data and guiding future exploration. This report seeks to catalyze a sustained and focused dialogue on how to best account for the abiotic background in the design of astrobiology spacecraft missions. By framing the issue both in terms of risks and scientific opportunities, we lay the groundwork for a richer, more integrated approach to the exploration of other worlds that benefits from continued cross-disciplinary input. We contend that advancing our understanding of the abiotic background now will directly inform and improve future astrobiological spacecraft missions, particularly in terms of payload selection and data interpretation.

The China National Space Administration has announced its Mars Sample Return mission Tianwen-3 to search for life on Mars. Tianwen-3 will be launched in 2028 and return ∼500 g of samples in 2031. Since the Tianwen-3's stationary lander will use a built-in 2 m drill to retrieve samples from depth and a robotic arm to scoop surface deposits, the strategy for selecting the landing site should differ from that of missions with rovers. Based on discoveries by the Curiosity and Perseverance rovers, we suggest that Tianwen-3 should land in an ancient endorheic lake basin where aqueous sediments and rich authigenic minerals are preserved due to the past presence of a stable body of water and high likelihood of a sustained period of vertical cycling of deep fluids. Our recent observations of brines and iron oxides precipitated by iron bacterial metabolism in a hyperarid, highly evaporative Mars analog basin further support the hypothesis that low-lying, closed crater basins on Mars are of high astrobiological value for upcoming sample return missions.

Astroecology has been proposed as a scientific field to study the diversity, structure, and function of ecosystems on Earth and other worlds; it is increasingly important as new space-borne observatories expand the search for inhabited planets and moons. Recent work has highlighted the relevance of ecological concepts across hierarchical levels from organisms to biospheres. However, we still lack general predictions about how processes such as species interactions and tradeoffs scale to affect food-web structure, biodiversity patterns, and life-planet feedbacks. Ecological processes emerge from basic physical and biological constraints. They generate patterns in biodiversity, ecosystem structure, and energy flow that are replicated across ecosystems, biomes, and taxa. These patterns generate "ecosignatures"-large-scale spatial or temporal signatures that reveal not just life but aspects of its ecological organization. Astroecological models thus provide a theoretical foundation for biosignature interpretation, comparative planetary habitability, and the universality of ecology.

Humanity's self-awareness drives the quest to understand the origins of life. Although Earth history has erased much of our planet's early biological evidence, Mars preserves ancient environments that may hold clues to life's emergence. Robotic explorations have confirmed that Mars once had liquid water and organic compounds, which suggests it was once habitable. However, definitive answers require analysis of pristine samples with advanced techniques in laboratories on Earth, which makes Mars Sample Return (MSR) missions a scientific imperative. NASA's Perseverance rover has begun caching samples, and China's Tianwen-3 mission plans a 2031 return. Yet NASA's MSR program faces cancellation, jeopardizing global efforts. Collaboration among NASA, the European Space Agency, and China's space agency may be the key to retrieving uncontaminated samples before human missions compromise them. A joint mission among these agencies could target the subsurface of an endorheic basin, where minerals such as magnetite may indicate recent vertical fluid cycles from the deep basin. Despite the low surface temperatures, hypersaline brines may transport subsurface microbes toward the martian regolith surface and carry fluids that could deposit authigenic minerals, enhancing preservation of mineral and organic biosignatures. International cooperation would maximize the likelihood of a successful mission, preserve the scientific integrity of samples returned to Earth, and offer humanity a unique opportunity to determine collaboratively whether life exists beyond Earth, fostering unity and shared progress in space exploration.

Whether meteorites brought ingredients necessary for the origin of life exogenously or they were produced endogenously on early Earth, having a prebiotic chemical inventory of organic compounds associated with meteorites is critical, as it represents a window into the organic compound building blocks available for the emergence of life. Understanding the prebiotic chemical reaction mechanisms of our solar system can aid in the distinction between abiotic and biotic processes in Earth's early history, which remains poorly constrained. In addition, these mechanisms can provide insight into what can be considered an abiosignature versus a biosignature. Such insight is key when considering the inventory of organic compounds intrinsic to meteorites, since extant life on Earth easily and readily contaminates meteorites. Formation mechanisms proposed for the organic compounds identified in meteorites demonstrate that complex compounds can arise from nine simple precursors found in the interstellar medium: water (H₂O), ammonia (NH₃), hydrogen cyanide (HCN), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), hydrogen (H₂), nitric oxide (NO), and sulfur dioxide (SO₂). Here we combine the mechanisms proposed for the formation of synthetically produced prebiotic organic compounds, noting their links to organic compounds observed on meteorites, and discuss the current weaknesses in our understanding of reaction yields and/or missing or poorly constrained processes. This review and analysis provide a resource of current knowledge of laboratory-based experimental data and identify future directions that are, or we recommend should, be explored.

This article summarizes the current state of knowledge regarding the destination for NASA's Dragonfly mission: Titan's Selk crater. We aim to foster an enhanced understanding of the environment in which Selk crater formed and how it evolved over time so that this knowledge may be used to interpret the data collected by the Dragonfly mission. In particular, we seek to constrain the likely products of the organic chemistry that occurred in its impact melt deposits. As such, we focus here on the crustal composition in the region where Selk crater formed, the molecules delivered by the impactor, the likely duration and evolution of aqueous chemistry in its melt deposits, and their expected reactants and chemical pathways. We conclude this article with recommendations for the best locations to sample the products of these reactions and describe how Dragonfly may use its instrumentation to identify and characterize the products of the aqueous chemistry at Selk crater.