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This paper presents a new approach, called the Modulus Weighting Method (MWM), for estimating the static stiffness of suction caisson foundations in layered soil conditions. The existing simplified design models for estimating caisson stiffness are limited to non-layered soil conditions, but layered conditions are often found in real-world scenarios. A three-dimensional (3D) finite element analysis (FEA) study was conducted to develop and validate the MWM approach, and the results showed that it performs well in comparison to the 3D FEA results while being much more computationally efficient.

Shear-rate weakening or strengthening behaviours can effectively control landslide runouts, defining sudden runaway sliding or years-long slow-creep phases. These behaviours are partly controlled by the properties of the basal material. Understanding its stress-strain-time response is crucial in physically-based assessments of landslide dynamics and the associated risk. We investigate the frictional resistance of a calcium bentonite, a kaolin and a quartz sand by means of a conventional ring-shear apparatus under normal stresses representative of landslide shear zones. Results for the fine-grained soils, in line with literature on pure clays, indicate important velocity strengthening, whereas small shear-rate effects were observed in sand. As long as effective stresses remain constant, a velocity strengthening response can exert a feedback that, under certain conditions, counteracts perturbations in boundary conditions and prevents fast runouts on pre-existing shear zones. Accordingly, we argue that specifically testing for shear-rate-dependency and incorporating observed behaviours in model formulations can be beneficial for better predicting landslide fates.

Pore fluids with different viscosities can exist in soils. While the effects of pore fluids have been investigated at the macro-scale, little is known about how they might affect the micromechanics. A novel apparatus allowing a single particle to be crushed while immersed in a liquid was built here. With the help of a high-speed microscope camera, the crushing processes of single silica sand particles immersed in glycerine were captured and the breakage modes were clarified. The immersion in glycerine leads to stronger particles with higher strains at failure compared with immersion in water or exposure to air. Moreover, the results of CRS tests revealed that saturation in glycerine made the sample significantly stiffer in compression as a result of less particle breakage compared with that in water or under dry conditions. The lower particle breakage at the macro-scale appeared to correspond to the higher strengths measured at the micro-scale. Highlights • A novel apparatus was built and used to investigate particle crushing process. • The crushing modes of a single sand particle immersed in glycerin were clarified. • A single particle immersed in glycerin tends to be stronger with a high deformation. • The macro-mechanical properties of sands were examined by CRS tests. • The micro and macro mechanical response of sands were associated and verified.

An elasto-plastic constitutive model for rockfill materials considering particle breakage is proposed. Although numerous constitutive models have been proposed for rockfill materials, most of them are mainly based on empirical results, without consideration of the physical meaning of their parameters. In the present work, a yield function is derived based on the evolution of microstructures formed by rockfill particles. The dilatancy equation is derived based on both the theory of breakage mechanics and the energy dissipation equations. The breakage-induced hardening is also formulated to account for both the volumetric and shearing hardening of rockfill materials. It is demonstrated that, without compromising the simplicity of the model, most of the parameters in the proposed constitutive model have concrete physical meanings. Comparison of the model simulation with experimental data shows that the proposed model can describe reasonably the static loading characteristics of rockfill materials within a wide range of confining stresses.

The capillary barrier effect (CBE) is employed in a large number of geotechnical applications to decrease deep percolation or increase slope stability. However, the micro-scale behaviour of CBE is rarely investigated, and thus hampers the scientific design of capillary barrier systems. This study uses microfluidics to explore the micro-scale behaviour of CBE. Capillarity-driven water flow processes from fine to coarse porous media with different pore topologies and sizes were performed and analysed. The experimental results demonstrate that the basic physics of CBE is the preferential water movement into the fine porous media due to the larger capillarity. The effects of CBE on water flow processes can be identified as delaying the occurrence of breakthrough into the coarse porous media and increasing the water storage of the fine porous media. The CBE can impede the increase of the normalised length and decrease the normalised width of the water front, suggesting that the two normalised parameters are potential indicators to assess the performance of CBE at the micro scale. CBE can be formed in square and honeycomb networks with the ratio of coarse to fine pore throat width larger than 2·0 when gravity is neglected, and its performance can be affected by pore topology and size.

Large soil movements arising from the installation of jack-up spudcan foundations may induce detrimental effects on piles supporting adjacent permanent jacket platforms. Particularly, in a dense sand-over-clay profile, there is a risk of spudcan rapid penetration due to underlying clay bearing capacity failure, known as spudcan punch-through failure, which can cause further damage to piles in the proximity. This study investigates the foundation interaction between the spudcan and adjacent pile in a sand-overlying-clay soil profile by way of centrifuge modelling. Issues investigated include thickness of the upper sand layer with incidence of sand plug beneath the spudcan and spudcan–pile clearance. The experimental findings reveal that spudcan punch-through hazard and the magnitude of induced pile moments amplifies primarily due to the increase in the thickness of the upper sand. In addition, the magnitude of induced pile moment in a sand-over-clay profile is significantly higher than that in a single clay profile because of the post-peak bearing behaviour observed in stratified soil, yielding to a greater risk to pile integrity. Soil pressure profiles on the piles are also back-analysed. Two generalised induced soil pressure profiles are deduced, with the first profile representing the onset of spudcan punch-through and the second profile denoting the situation of post-punch-through failure.

This empirical study tried to understand the effects of over-the-top (OTT) streaming platforms on the Indian film industry. The paper analyzes the impact of OTT on both users and technicians of the film industry, highlighting both positive and negative effects. The objective of the study is to explore the changes in the film industry because of the rise in OTT platforms. The methodology of the research involved sending a questionnaire to 100 individuals, which included both users and technicians of the Indian film industry. The sampling techniques used in the study were convenience sampling and snowball sampling. The data collected through the questionnaire was analyzed using statistical tools to get meaningful insights. The study found that the introduction of OTT platforms has led to a significant change in the Indian film industry. While it has provided a platform for small-budget films and new talent, it has also led to concerns about censorship and revenue loss for traditional distribution channels. The study also found that the viewing habits of users have changed, and they now prefer to consume content on their own terms, rather than following traditional schedules and methods. Overall, this study provides valuable insights into the effects of OTT platforms on the Indian film industry. The findings of this study can be used by industry to make informed decisions about the future of the film industry in the digital age.

This study presents the use of rubber grids (RGs) fabricated from end-of-life conveyor belts (i.e. discarded from the mining industry) to improve the performance of ballast tracks. The square apertures of these recycled rubber sheets were cast using a waterjet cutting process. A series of large-scale impact tests were performed on ballast specimens stabilised with three different grids of varied effective area ratios (KA.eff) to evaluate their effectiveness in mitigating the applied impact forces, in relation to both displacement and breakage of the ballast aggregates. Smart Ballast particles with motion-sensing capabilities were adopted to monitor the interaction between the grid and ballast assembly. The impact test results indicate that the inclusion of a RG decreases the deformation and breakage of ballast as well as reduces its vibrations. This study demonstrates that these recycled RGs with optimum effective area ratios can be more effective than conventional polymer geogrids, apart from the obvious environmental benefits.

Open caissons are an increasingly common means of constructing underground storage and attenuation tanks as well as launch and reception shafts for tunnel-boring machines. The caisson walls typically feature a tapered base, referred to as the ‘cutting face’, to aid the sinking process by reducing the vertical soil reaction. The primary aim of this paper is to explore the influence of the caisson cutting face inclination angle on the vertical soil reaction in sand. Both finite-element limit analysis and finite-element analysis are adopted for this purpose. The effects of cutting face roughness, external embedment depth and caisson radius are also investigated. The results show that the influence of the cutting face inclination angle on the bearing capacity is highly dependent on both the soil friction angle and the roughness of the cutting face. A reduction in the caisson radius is also shown to cause a significant increase in the vertical soil reaction. The numerical output is used to inform the development of a new closed-form analytical approach amenable for use in routine design. The design method is shown to provide a high-fidelity representation of the numerical output.

Significant reduction in the brittleness of sandy silt/silty sand tailings at high stresses has frequently been observed in laboratory element testing due to curvature of the critical state line and the limiting compression curve. This has led to discussions regarding the range of effective stresses across which such materials can exhibit brittle undrained shearing such that flow liquefaction could occur. However, much testing of such tailings appears to involve saturation of the tailings under relatively low-confining stresses. This differs from the potential in situ loading within a filtered tailings stack, where material placed in a loose, unsaturated state may be subjected to significant overburden pressures prior to potential subsequent saturation. A series of isotropically consolidated triaxial tests were carried out on sandy silt gold tailings to investigate the effects of the saturation process of loose moist-tamped specimens occurring at different confining stresses. The tests indicated much looser states were achievable when saturation occurred at higher confining pressures, with resulting undrained shearing for such specimens being of similar magnitudes of brittleness as observed in flow liquefaction case histories. Consideration of saturation overburden pressure of filtered tailings stacks therefore appears warranted.

Integral bridges are preferred on infrastructure schemes as they have lower maintenance costs than a conventional jointed bridge. A key aspect of integral bridge design is the assessment of long-term passive resistance that develops in the abutment backfill due to seasonal movements of the superstructure. This resistance is currently defined by an intermediate earth pressure coefficient termed K*, and is typically evaluated using the limit equilibrium (LE) approach prescribed in BSI PD-6694-1:2011+A1:2020. This paper adopts the alternative numerical design approach and investigates the development of K* behind full-height abutments using soil–structure interaction (SSI) modelling in Plaxis-2D software. The study demonstrates that mobilised passive resistance is primarily a function of backfill and structural stiffnesses, and that the current LE approach does not capture the backfill resistance profile correctly. The effectiveness of the SSI method was verified by comparison to the LE method. The current study provides an SSI methodology that is an efficient design approach, and which is suitable for a wide variety of integral bridge arrangements beyond the current LE method applicability.

An oxygen-rich atmosphere is essential for complex animals. The early Earth had an anoxic atmosphere, and understanding the rise and maintenance of high O2 levels is critical for investigating what drove our own evolution and for assessing the likely habitability of exoplanets. A growing number of techniques aim to reproduce changes in O2 levels over the Phanerozoic Eon (the past 539 million years). We assess these methods and attempt to draw the reliable techniques together to form a consensus Phanerozoic O2 curve. We conclude that O2 probably made up around 5–10% of the atmosphere during the Cambrian and rose in pulses to ∼15–20% in the Devonian, reaching a further peak of greater than 25% in the Permo-Carboniferous before declining toward the present day. Evolutionary radiations in the Cambrian and Ordovician appear consistent with an oxygen driver, and the Devonian “Age of the Fishes” coincides with oxygen rising above 15% atm. ▪ An oxygen-rich atmosphere is essential for complex animals such as humans. ▪ We review the methods for reconstructing past variation in oxygen levels over the past 539 million years (the Phanerozoic Eon). ▪ We produce a consensus plot of the most likely evolution of atmospheric oxygen levels. ▪ Evolutionary radiations in the Cambrian, Ordovician, and Devonian periods may be linked to rises in oxygen concentration.

Terrestrial plants have transformed Earth's surface environments by altering water, energy, and biogeochemical cycles. Studying vegetation-climate interaction in deep time has necessarily relied on modern-plant analogs to represent paleo-ecosystems—as methods for reconstructing paleo- and, in particular, extinct-plant function were lacking. This approach is potentially compromised given that plant physiology has evolved through time, and some paleo-plants have no clear modern analog. Advancements in the quantitative reconstruction of whole-plant function provide new opportunities to replace modern-plant analogs and capture age-specific vegetation-climate interactions. Here, we review recent investigations of paleo-plant performance through the integration of fossil and geologic data with process-based ecosystem- to Earth system–scale models to explore how early vascular plants responded to and influenced climate. First, we present an argument for characterizing extinct plants in terms of ecological and evolutionary theory to provide a framework for advancing reconstructed vegetation-climate interactions in deep time. We discuss the novel mechanistic understanding provided by applying these approaches to plants of the late Paleozoic ever-wet tropics and at higher latitudes. Finally, we discuss preliminary applications to paleo-plants in a state-of-the-art Earth system model to highlight the potential implications of different plant functional strategies on our understanding of vegetation-climate interactions in deep time. ▪ For hundreds of millions of years, plants have been a keystone in maintaining the status of Earth's atmosphere, oceans, and climate. ▪ Extinct plants have functioned differently across time, limiting our understanding of how processes on Earth interact to produce climate. ▪ New methods, reviewed here, allow quantitative reconstruction of extinct-plant function based on the fossil record. ▪ Integrating extinct plants into ecosystem and climate models will expand our understanding of vegetation's role in past environmental change.

The abundance of pond ash and its resemblance to natural sand encourages its use as a substitute for sand in sand–bentonite (SB) liner material. Compaction water content influences the geoengineering properties of cohesive soil to a great extent. Accordingly, the compaction, strength, permeability and shrinkage characteristics of both pond ash–bentonite (PAB) and SB mixes are investigated at standard and modified Proctor compaction energies at various water contents to support the recommendation of the PAB mixture as an alternative landfill liner. At similar compaction conditions, the PAB mix exhibits higher unconfined compressive strength (UCS) and hydraulic conductivity than the SB mix. The UCS values of mixes compacted on the dry side of optimum are higher than those of mixes compacted on the wet side. Dry-side compacted mixes exhibit a reduction in hydraulic conductivity with permeation time, whereas no substantial reduction in hydraulic conductivity is noticed for wet-side compacted mixes. Furthermore, the volumetric shrinkage of both PAB and SB mixes is within the permissible value of 4%, for a wide range of water variation from the dry to the wet side of optimum. The observed mechanical properties are correlated to the shape of coarse fraction particles and the corresponding microstructural arrangements of the compacted specimens.

As atmospheric carbon dioxide concentrations rise and climate change becomes more destructive, geoengineering has become a subject of serious consideration. By reflecting a fraction of incoming sunlight, solar geoengineering could cool the planet quickly, but with uncertain effects on regional climatology, particularly hydrological patterns. Here, we review recent work on projected hydrologic outcomes of solar geoengineering, in the context of a robust literature on hydrological responses to climate change. While most approaches to solar geoengineering are expected to weaken the global hydrologic cycle, regional effects will vary based on implementation method and strategy. The literature on the hydrologic outcomes and impacts of geoengineering demonstrates that its implications for human welfare will depend on assumptions about underlying social conditions and objectives of intervention as well as the social lens through which projected effects are interpreted. We conclude with suggestions to reduce decision-relevant uncertainties in this novel field of Earth science inquiry. ▪ The expected hydrological effects of reducing insolation are among the most uncertain and consequential impacts of solar geoengineering (SG). ▪ Theoretical frameworks from broader climate science can help explain SG's effects on global precipitation, relative humidity, and other aspects of hydroclimate. ▪ The state of the knowledge on hydrological impacts of SG is unevenly concentrated among regions. ▪ Projected hydrological impacts from SG are scenario dependent and difficult to characterize as either harmful or beneficial.

A science-based understanding of climate change and potential mitigation and adaptation options can provide decision makers with important guidance in making decisions about how best to respond to the many challenges inherent in climate change. In this review we provide an evidence-based heuristic for guiding efforts to share science-based information about climate change with decision makers and the public at large. Well-informed decision makers are likely to make better decisions, but for a range of reasons, their inclinations to act on their decisions are not always realized into effective actions. We therefore also provide a second evidence-based heuristic for helping people and organizations change their climate change–relevant behaviors, should they decide to. These two guiding heuristics can help scientists and others harness the power of communication and behavior science in service of enhancing society's response to climate change. ▪ Many Earth scientists seeking to contribute to the climate science translation process feel frustrated by the inadequacy of the societal response. ▪ Here we summarize the social science literature by offering two guiding principles to guide communication and behavior change efforts. ▪ To improve public understanding, we recommend simple, clear messages, repeated often, by a variety of trusted and caring messengers. ▪ To encourage uptake of useful behaviors, we recommend making the behaviors easy, fun, and popular.

Defining the age of the Moon has proven to be an elusive task because it requires reliably dating lunar samples using radiometric isotopic systems that record fractionation of parent and daughter elements during events that are petrologically associated with planet formation. Crystallization of the magma ocean is the only event that unambiguously meets this criterion because it probably occurred within tens of millions of years of Moon formation. There are three dateable crystallization products of the magma ocean: mafic mantle cumulates, felsic crustal cumulates, and late-stage crystallization products known as urKREEP (uniform residuum K, rare earth elements, and P). Although ages for these materials in the literature span 200 million years, there is a preponderance of reliable ages around 4.35 billion years recorded in all three lunar rock types. This age is also observed in many secondary crustal rocks, indicating that they were produced contemporaneously (within uncertainty of the ages), possibly during crystallization and overturn of the magma ocean. ▪ The duration of planet formation is key information in understanding the mechanisms by which the terrestrial planets formed. ▪ Ages of the oldest lunar rocks range widely, reflecting either the duration of Moon formation or disturbed ages caused by impact metamorphism. ▪ Ages determined for compositionally distinct crust and mantle materials produced by lunar magma ocean differentiation cluster near 4.35 Gyr. ▪ The repeated occurrence of 4.35 Gyr ages implies that Moon formation occurred late in Solar System history, likely by giant impact into Earth.

Uncertainty about sea-level rise is dominated by uncertainty about iceberg calving, mass loss from glaciers or ice sheets by fracturing. Review of the rapidly growing calving literature leads to a few overarching hypotheses. Almost all calving occurs near or just downglacier of a location where ice flows into an environment more favorable for calving, so the calving rate is controlled primarily by flow to the ice margin rather than by fracturing. Calving can be classified into five regimes, which tend to be persistent, predictable, and insensitive to small perturbations in flow velocity, ice characteristics, or environmental forcing; these regimes can be studied instrumentally. Sufficiently large perturbations may cause sometimes-rapid transitions between regimes or between calving and noncalving behavior, during which fracturing may control the rate of calving. Regime transitions underlie the largest uncertainties in sea-level rise projections, but with few, important exceptions, have not been observed instrumentally. This is especially true of the most important regime transitions for sea-level rise. Process-based models informed by studies of ongoing calving, and assimilation of deep-time paleoclimatic data, may help reduce uncertainties about regime transitions. Failure to include calving accurately in predictive models could lead to large underestimates of warming-induced sea-level rise. ▪ Iceberg calving, the breakage of ice from glaciers and ice sheets, affects sea level and many other environmental issues. ▪ Modern rates of iceberg calving usually are controlled by the rate of ice flow past restraining points, not by the brittle calving processes. ▪ Calving can be classified into five regimes, which are persistent, predictable, and insensitive to small perturbations. ▪ Transitions between calving regimes are especially important, and with warming might cause faster sea-level rise than generally projected.

I describe my career journey from a young girl in Cameroon, West Africa, to a trailblazing geophysicist to my current role as dean. I chronicle my time as a student, the transition to being an early career faculty, launching my research career, and ultimately finding my way to administration. Along the way I helped pioneer biogeophysics as a subdiscipline in geophysics while simultaneously maintaining an international research program in continental rift tectonics. I also describe the many intersectionalities in my life including being the first Black woman in many spaces, being a champion for student success, developing a diverse talent pipeline by enhancing diversity in the geosciences, and navigating academic job searches as part of a dual-career couple. Finally, I acknowledge all those who helped shape my career including the many students I had the opportunity to mentor. ▪ Many underrepresented minority geoscientists lack the social capital and professional networks critical for their success. ▪ Geoscience departments must be intentional and deliberate in promoting and ensuring more inclusive workplace environments. ▪ Dual-career couples remain a major challenge, impacting retention and recruitment of top talent; universities should provide resources to alleviate this challenge. ▪ Biogeophysics has untapped potential for advancing understanding of subsurface biogeochemical processes and the search for life in extreme environments. ▪ To date, considerable speculation remains regarding the fundamental geodynamic processes that initiate and sustain the evolution of magma-deficient rifts.

Kimberlite-borne xenolithic eclogites, typically occurring in or near cratons, have long been recognized as remnants of Precambrian subducted oceanic crust that have undergone partial melting to yield granitoids similar to the Archean continental crust. While some eclogitized oceanic crust was emplaced into cratonic lithospheres, the majority was deeply subducted to form lithologic and geochemical heterogeneities in the convecting mantle. If we accept that most xenolithic eclogites originally formed at Earth's surface, then their geodynamic significance encompasses four tectonic environments: ( a) spreading ridges, where precursors formed by partial melting of convecting mantle and subsequent melt differentiation; ( b) subduction zones, where oceanic crust was metamorphosed and interacted with other slab lithologies; ( c) the cratonic mantle lithosphere, where the eclogite source was variably modified subsequent to emplacement in Mesoarchean to Paleoproterozoic time; and ( d) the convecting mantle, into which the vast majority of subduction-modified oceanic crust not captured in the cratonic lithosphere was recycled. ▪ Xenolithic eclogites are fragments of ca. 3.0–1.8 Ga oceanic crust and signal robust subduction tectonics from the Mesoarchean. ▪ Multiple constraints indicate an origin as variably differentiated oceanic crust, followed by subduction metamorphism, and prolonged mantle residence. ▪ Xenolithic eclogites thus permit investigation of deep geochemical cycles related to recycling of Precambrian oceanic crust. ▪ They help constrain asthenosphere thermal plus redox evolution and contribute to cratonic physical properties and mineral endowments.

The strength of lithospheric plates is a central component of plate tectonics, governed by brittle processes in the shallow portion of the plate and ductile behavior in the deeper portion. We review experimental constraints on ductile deformation of olivine, the main mineral in the upper mantle and thus the lithosphere. Olivine deforms by four major mechanisms: low-temperature plasticity, dislocation creep, dislocation-accommodated grain-boundary sliding (GBS), and diffusion-accommodated grain-boundary sliding (diffusion creep). Deformation in most of the lithosphere is dominated by GBS, except in shear zones—in which diffusion creep dominates—and in the brittle-ductile transition—in which low-temperature plasticity may dominate. We find that observations from naturally deformed rocks are consistent with extrapolation of the experimentally constrained olivine flow laws to geological conditions but that geophysical observations predict a weaker lithosphere. The causes of this discrepancy are unresolved but likely reside in the uncertainty surrounding processes in the brittle-ductile transition, at which the lithosphere is strongest. ▪ Ductile deformation of the lithospheric mantle is constrained by experimental data for olivine. ▪ Olivine deforms by four major mechanisms: low-temperature plasticity, dislocation creep, dislocation-accommodated grain-boundary sliding, and diffusion creep. ▪ Observations of naturally deformed rocks are consistent with extrapolation of olivine flow laws from experimental conditions. ▪ Experiments predict stronger lithosphere than geophysical observations, likely due to gaps in constraints on deformation in the brittle-ductile transition.

Machine learning (ML) is a collection of methods used to develop understanding and predictive capability by learning relationships embedded in data. ML methods are becoming the dominant approaches for many tasks in seismology. ML and data mining techniques can significantly improve our capability for seismic data processing. In this review we provide a comprehensive overview of ML applications in earthquake seismology, discuss progress and challenges, and offer suggestions for future work. ▪ Conceptual, algorithmic, and computational advances have enabled rapid progress in the development of machine learning approaches to earthquake seismology. ▪ The impact of that progress is most clearly evident in earthquake monitoring and is leading to a new generation of much more comprehensive earthquake catalogs. ▪ Application of unsupervised approaches for exploratory analysis of these high-dimensional catalogs may reveal new understanding of seismicity. ▪ Machine learning methods are proving to be effective across a broad range of other seismological tasks, but systematic benchmarking through open source frameworks and benchmark data sets are important to ensure continuing progress.

The current rapid increase in atmospheric CO2, linked to the massive use of fossil fuels, will have major consequences for our climate and for living organisms. To understand what is happening today, it is informative to look at the past. The evolution of the carbon cycle, coupled with that of the past climate system and the other coupled elemental cycles, is explored in the field, in the laboratory, and with the help of numerical modeling. The objective of numerical modeling is to be able to provide a quantification of the processes at work on our planet. Of course, we must remain aware that a numerical model, however complex, will never include all the relevant processes, impacts, and consequences because nature is complex and not all the processes are known. This makes models uncertain. We are still at the beginning of the exploration of the deep-time Earth. In the present contribution, we review some crucial events in coupled Earth-climate-biosphere evolution over the past 540 million years, focusing on the models that have been developed and what their results suggest. For most of these events, the causes are complex and we are not able to conclusively pinpoint all causal relationships and feedbacks in the Earth system. This remains a largely open scientific field. ▪ The era of the pioneers of geological carbon cycle modeling is coming to an end with the recent development of numerical models simulating the physics of the processes, including climate and the role of vegetation, while taking into account spatialization. ▪ Numerical models now allow us to address increasingly complex processes, which suggests the possibility of simulating the complete carbon balance of objects as complex as a mountain range. ▪ While most of the processes simulated by models are physical-chemical processes in which the role of living organisms is taken into account in a very simple way, via a limited number of parameters, models of the carbon cycle in deep time coupled with increasingly complex ecological models are emerging and are profoundly modifying our understanding of the evolution of our planet's surface.

Carbonate minerals contain stable isotopes of carbon and oxygen with different masses whose abundances and bond arrangement are governed by thermodynamics. The clumped isotopic value Δi is a measure of the temperature-dependent preference of heavy C and O isotopes to clump, or bond with or near each other, rather than with light isotopes in the carbonate phase. Carbonate clumped isotope thermometry uses Δi values measured by mass spectrometry (Δ47, Δ48) or laser spectroscopy (Δ638) to reconstruct mineral growth temperature in surface and subsurface environments independent of parent water isotopic composition. Two decades of analytical and theoretical development have produced a mature temperature proxy that can estimate carbonate formation temperatures from 0.5 to 1,100°C, with up to 1–2°C external precision (2 standard error of the mean). Alteration of primary environmental temperatures by fluid-mediated and solid-state reactions and/or Δi values that reflect nonequilibrium isotopic fractionations reveal diagenetic history and/or mineralization processes. Carbonate clumped isotope thermometry has contributed significantly to geological and biological sciences, and it is poised to advance understanding of Earth's climate system, crustal processes, and growth environments of carbonate minerals. ▪ Clumped heavy isotopes in carbonate minerals record robust temperatures and fluid compositions of ancient Earth surface and subsurface environments. ▪ Mature analytical methods enable carbonate clumped Δ47, Δ48, and Δ638 measurements to address diverse questions in geological and biological sciences. ▪ These methods are poised to advance marine and terrestrial paleoenvironment and paleoclimate, tectonics, deformation, hydrothermal, and mineralization studies.

Planets are expected to conclude their growth through a series of giant impacts: energetic, global events that significantly alter planetary composition and evolution. Computer models and theory have elucidated the diverse outcomes of giant impacts in detail, improving our ability to interpret collision conditions from observations of their remnants. However, many open questions remain, as even the formation of the Moon—a widely suspected giant-impact product for which we have the most information—is still debated. We review giant-impact theory, the diverse nature of giant-impact outcomes, and the governing physical processes. We discuss the importance of computer simulations, informed by experiments, for accurately modeling the impact process. Finally, we outline how the application of probability theory and computational advancements can assist in inferring collision histories from observations, and we identify promising opportunities for advancing giant-impact theory in the future. ▪ Giant impacts exhibit diverse possible outcomes leading to changes in planetary mass, composition, and thermal history depending on the conditions. ▪ Improvements to computer simulation methodologies and new laboratory experiments provide critical insights into the detailed outcomes of giant impacts. ▪ When colliding planets are similar in size, they can merge or escape one another with roughly equal probability, but with different effects on their resulting masses, densities, and orbits. ▪ Different sequences of giant impacts can produce similar planets, encouraging the use of probability theory to evaluate distinct formation hypothesis.

Mimas, the smallest and innermost of Saturn's mid-sized moons, has a heavily cratered surface devoid of the intricate fracture systems of its neighbor, Enceladus. However, Cassini measurements identified a signature of an ocean under Mimas’ ice shell, although a frozen ice shell over a rocky interior could not be ruled out. The Mimas ocean hypothesis has stimulated inquiry into Mimas’ geologic history and orbital evolution. Here, we summarize the results of these investigations, which (perhaps surprisingly) are consistent with an ocean-bearing Mimas as long as it is geologically young. In that case, a ring origin for Mimas is favored over primordial accretion. An independently developed model for the formation of a gap in Saturn's rings provides a potential mechanism for generating a late-stage ocean within Mimas and may have assisted in the development of Enceladus’ ocean and associated geologic activity. Rather than a battered relic, Mimas may be the youngest ocean moon in the Saturn system, destined to join Enceladus as an active world in the future. The presence of oceans within Saturn's mid-sized moons also has implications for the habitability of Uranus’ moons; the Uranus system was chosen as the highest priority target for the next NASA Flagship-class mission. ▪ Models of Mimas’ tides and rotation state support a present-day internal ocean. ▪ Mimas’ craters, impact basin, and lack of widespread tectonism are compatible with a stable/warming ocean. ▪ The formation of the Cassini Division within Saturn's rings provides a potential pathway to a present-day ocean within Mimas. ▪ If Mimas has an ocean today, it is geologically young.