物理与天体物理最新文献

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.