Carnegie Institution for Science

Compositional data (CoDa) are prevalent in environmental research. They represent parts of a whole, such as percentages, proportions, and relative or absolute abundances. They are arrays of positive data that convey relevant information in the ratios between their components. Standard statistical techniques developed for real random observations often yield spurious results and are therefore unsuitable for CoDa, which has unique geometric properties. CoDa analysis is now widely acknowledged across various research fields, ranging from geoscience to social science, with a recent surge in popularity in microbial genomics. However, its adoption remains limited in natural organic matter (NOM) research, despite NOM data from key analytical tools such as mass spectrometry, fluorescence spectroscopy, and nuclear magnetic resonance spectroscopy all being compositional. Given the structural similarity between NOM and high-throughput sequencing data, for which CoDa analysis has been successfully adopted, we argue that CoDa analysis should also be consistently integrated into NOM research to prevent analytical pitfalls and misleading inferences. A few pioneering studies have applied CoDa analysis to NOM data, and a wide array of useful open-source tools are already available. This paper discusses step-by-step the application of CoDa analysis to NOM research, using ultrahigh-resolution mass spectrometry data as an illustrative example. The goal of the study is to provide the community with an overview of CoDa analysis and guide them on how to use it in practice.

Abstract We present a major update to the open-source atmospheric modeling package PICASO , designed for simulating the thermal structure and spectra of hydrogen-rich atmospheres of brown dwarfs and exoplanets. This release, PICASO 4.0 , expands upon the existing radiative-convective equilibrium model framework by incorporating several new capabilities. Key additions include the integration of Virga for self-consistent cloud modeling, new flexible treatments for rainout and cold trapping of volatile species, and support for photochemistry. We also introduce a parameterized energy injection scheme to simulate additional external or internal heating processes. These features are motivated by lessons from recent JWST observations that reveal the prevalence of nonequilibrium chemistry and clouds. We benchmark the new functionalities against previously published results in the literature, including the Sonora Diamondback grid, energy injected atmospheres, patchy cloud models, and other photochemical models of WASP-39b. PICASO continues to be actively developed as an open-source package aimed at enabling reproducible, community-driven atmospheric modeling of all substellar objects.

Pressure-temperature (P-T) estimates from subduction-related metamorphic rocks such as eclogites and blueschists are often used to constrain the thermal conditions of fossil subduction zone plate interfaces. However, the metamorphic rock record indicates peak temperatures 100-300°C warmer on average than those predicted by geodynamic models for modern subduction zones.. To shed light on the difference in the fossil and modern subduction zone thermal structures, we compare newly acquired P-T estimates using quartz-in-garnet and zircon-in-garnet elastic thermobarometry combined with Zr-in-rutile thermometry to newly constructed geodynamic models for the thermal evolution of the Rio San Juan Complex, Dominican Republic. The geodynamic models are 2-D coupled kinematic-dynamic models that use the fossil subduction parameters, such as time-dependent convergence velocity and plate age. Global plate reconstruction models provide constraints on these parameters. Data from regional geological and petrological studies constrain the duration of subduction and the thermal history of the subducting plate. New analyses on an eclogite sample reveal a counter-clockwise pressure-temperature (P-T) path, with peak conditions at ~1.7 GPa and ~650ºC. Previous thermobarometric studies on the same sample indicate similar temperatures but significantly higher peak pressures, up to ~2.3 GPa, during the early stage of subduction around 110–104 Ma. In contrast, lower-grade blocks indicate isobaric cooling to ~400ºC and clockwise P-T paths during a later stage (80–62 Ma). Our thermal modeling results indicate that subduction initiation between two relatively young tectonic plates (< 30 Ma) can explain the relatively low-P, high-T data from both new and previous analyses. However, the highest pressures derived by the previous study require a rapid deepening of the maximum depth of slab-mantle decoupling during the early stages of subduction. Such deepening can be explained by a plate velocity increase around 110 Ma. Our modeling results further indicate the subduction rate increase results in significant cooling of the interface at a given depth, consistent with the isobaric cooling observed in the rock record. Migration of the spreading center across the study area may explain the change from counter-clockwise to clockwise paths, and higher temperature gradients of some of the blocks.

Age models for many sediment records are imprecise at best and inaccurate at worst, hindering our ability to closely compare different proxy records, track variations in regional responses to climate change, and understand how Earth’s climate sensitivity changed through time. We must tackle the challenge of imprecise age models if we are to make significant advances in paleoclimatic reconstructions and near-future climate projections. A coordinated, global, cross-disciplinary research network is required to address the immense challenges of establishing accurate age calibrations for sedimentary records covering the past 100 million years of Earth's climate history.We have launched an international, coordinated effort to revise, recalibrate, and synchronize the dating tools available to paleoclimatologists – i.e., local and regional information obtained from chemo-, bio- and magnetostratigraphy, as well as radioisotopic geochronology – by unifying these approaches with astrochronology. Synchronizing proxy data at orbital-scale resolution is critical as it allows for detailed reconstructions of climate variability and for resolving the sequence of events in climate-relevant processes over millions of years in the past. Our nascent initiative, the Time-Integrated Matrix for Earth Sciences (TIMES) program, will facilitate the interaction of the climate proxy and modeling communities with the timescale-generating community and astronomers, to deliver highly synchronized, accurate, and precise timelines for these sedimentary climate records.We will share insights from our Kickoff Workshop in August 2025, at which the TIMES working group began defining key components of a Science Plan for the first five-year long phase of TIMES. We invite further involvement of members of the timescale- and proxy-generating communities, as well as climate modelers, to contribute to our efforts to tackle this colossal scientific challenge as we build our inclusive international collaboration.

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 Central and Eastern United States (CEUS) earthquakes are less common than those in the tectonically active West Coast, but their significance is elevated due to higher population densities, less-attenuating bedrock geology, variable site-amplification effects, and a higher proportion of structures prone to damage from shaking. Associating CEUS earthquake focal mechanisms with causative crustal faults is challenging due to a lack of mapped faults. Aftershock productivity of CEUS earthquakes is difficult to predict because it is highly variable, displaying globally typical behavior in some regions (Wu et al., 2015; Wu and Chapman, 2017) and low decay rates (Stein and Liu, 2009; Calais et al., 2016; Toda and Stein, 2018) in others. Here, we study the aftershock sequence of an unusual Mw 4.24 CEUS earthquake that occurred below the Atlantic Coastal Plain east of Dover, Delaware, in late 2017. We analyze data from a temporary 14-station network and use template matching to search for aftershocks, which we locate using a custom 1D velocity model. We find aftershock locations favoring slip on a northwest–southeast-striking fault oblique to the presumed fault where the mainshock was located. We document an unusually low a value and large magnitude difference between the mainshock and the largest aftershock, as well as an average aftershock decay p value. Factors proposed to explain variations in aftershock productivity include fault alignment relative to the prevailing stress field (Hardebeck, 2010) and low productivity after a high stress drop (Wetzler et al., 2018). We test these hypotheses in relation to the 2017 Delaware earthquake aftershocks, showing the Delaware earthquake had a stress drop of 35 MPa, normal for an intraplate region (Boyd et al., 2017), and had favorable alignment for aftershock thrust faulting. We therefore propose a small fault of possible pre-Mesozoic origin, limiting the productivity observed.

Abstract We report observations of main-belt asteroid 2025 VZ 8 using multiple telescopes from UT 2025 November 24 to UT 2025 December 23 that confirm the presence of visible comet-like activity. These observations were motivated by online reports that an abrupt brightening event may have led to the object’s discovery on UT 2025 November 9. In all observations reported here, the object displays a tapered tail approximately 3″ long aligned with the antisolar direction. The object has an asteroidal Tisserand parameter value with respect to Jupiter ( T J = 3.371), and is thus considered an active asteroid. We measure an average apparent r ′ -band magnitude of m r ∼ 21.6 mag over the reported observing period. Due to the sudden appearance of activity far from perihelion, we suggest that the activity is more likely due to an impact or rotational destabilization, rather than sublimation.

Rapid urban development has intensified soil sealing by impervious surfaces, contributing to extreme urban heat, flooding, and health risks. Although research on the impact of impervious surfaces on urban heat has grown in recent years, most studies overlook variations in surface characteristics, such as surface color, which influence urban heat. Consequently, city-wide data on sub-categorized impervious surfaces remain limited. This research fills this gap by using high-resolution remote-sensing imagery classification in ArcGIS Pro to map surface characteristics in Pittsburgh, Pennsylvania, and examine their relationship with land surface temperatures (LST) and social vulnerability. Results show that impervious surfaces cover 55% of the city, including 22% roofs, 30.7% roads and 2.3% parking lots, with 52% of these surfaces classified as dark. On average, historically redlined neighborhoods are 2.6 °C (4.7 °F) hotter and contain a higher proportion of dark surfaces. These results underscore the role of surface color and composition in shaping urban thermal inequities and emphasize the need for evidence-based decision-making in surface material selection to build more equitable and sustainable cities. • Pittsburgh’s overall roofs, streets, and parking lots are 52% dark. • Summer surface temperatures can reach 68.6 °C (155.4 °F). • Historically redlined neighborhoods have 12.6% more dark surfaces and are 2.6 °C (4.7°F) hotter. • Each 1% more dark surface adds 0.18 °C (0.32 °F) to summer LST. • Dark and light surfaces show modest correlations with SVI across Pittsburgh.