In response to the NERC Theme Action (TA) we propose a consortium among scientists at seven UK institutions and with three international partners centred on the 'The Volatile Legacy of the Early Earth'. Earth's habitability is strongly linked to its inventory and cycling of volatiles, which today are coupled to plate tectonics, but we still have little notion as to how our planet found itself in this near-ideal 'Goldilocks' state where the volatile mix is 'just right'. Was it simply a matter of being at the right solar distance with the right supply of volatiles? Or were the details of the chemistry and dynamics of early accretion and differentiation crucial to the eventual outcome? Such questions are of critical importance for understanding our own planets development, and given the burgeoning field of exo-planet discovery, they gain extra piquancy for gauging the probability of life elsewhere. In this proposal we investigate how the early evolution of volatiles on Earth set the stage for habitability. Planets grow by collisions and these violent events may lead to loss of the volatiles carried within the impacting bodies. We will explore with numerical modeling the conditions under which the volatiles are retained or lost in planetesimal collisions. We will also assess the likelihood that volatiles were delivered to Earth 'late', namely after the maelstrom of major collisions was finished and the planet was largely constructed, by studying the element S and notably its geochemical twin, Se. We will constrain the process of loss to the core and the isotopic signature imparted by this process. We will further use isotopic measurements as finger-prints of the origin of modern Se, and will find out whether it corresponds to any known meteorite type, or if it was possibly delivered by comets. The Moon provides further clues to the origin of the Earth, and Interrogating the significance of the recently refined volatile inventory of the Moon requires new experiments under appropriate conditions. The energy generated by planetary collisions inevitably results in large-scale melting. The solubility and chemical nature of volatiles within a magma ocean controls whether or not gases are carried into the interior of the planet or left in the atmosphere. Volatiles retained in the magma ocean may become part of a deep mantle volatile cycle or become permanently sequestered in deep reservoirs. We will redress this issue with a series of experiments that simulate conditions of the early magma ocean. We will further investigate the stability of phases in the lower mantle that can potentially hold volatile elements if delivered to great depths by solubility in a convecting magma ocean. Using seismic and modeling techniques, we will assess if any remnants of such stored volatiles are currently 'visible' in the deepest mantle. The influence of the core on volatile budgets is potentially great because of its size, but volatile solubility is poorly known. We will examine the solubility of hydrogen, carbon and nitrogen in liquid metal at high pressures and temperatures. In this consortium we will also create a cohort of PhD students and supervisors who work as part of a large team to piece together the evidence for Earth's volatile evolution using inclusions trapped in diamonds. These may be the key 'space-time' capsules that can link experimental and theoretical work on early Earth evolution to present-day volatile budgets and fluxes in the deep Earth. The questions raised in this proposal are complex and require a wide range of information in order to provide meaningful answers. It is our goal to establish a much-improved understanding of how Earth initially became a habitable planet, and to build a solid foundation on which further UK research can continue to lead the way in this exciting field. This will be the ultimate legacy of this consortium, and through links to other consortia, of the entire Theme Action.

Decarbonisation of the UK's energy system will require substantial action at a regional and local level. Therefore, the UK's energy system is growing rapidly to a more decentralised model by 2050 with a great level of small-scale electricity and heat generation at the distribution level, where wind and solar renewable energies will play a large role. However, the intermittent nature of these renewable sources presents a great challenge in energy generation and load balance maintenance to ensure stability and reliability of the power network. This highlights the need for electricity storage technologies as they provide flexibility to store excess electricity for times when it is in demand. The majority of recent installations deploy fast response electricity storage systems (e.g. batteries) with short-duration electricity storage (minutes-days) and short-discharge duration of up to 4 hours. However, technologies with long-duration electricity storage (days-weeks) and medium-duration discharge of over 4 hours, with negligible capacity and efficiency degradation are required to ensure power supply security in all weather conditions (e.g. wind or solar energies are not available for several days). There are several possible technologies for long-duration energy storage, e.g., pumped-hydro storage, liquid air energy storage and compressed air energy storage (CAES). Among them, adiabatic CAES systems (ACAES) has the lowest installed energy capital costs (2-50$/kWh) for a wide range of storage applications from micro scale (few kW) to large scale (few MW). In conventional ACAES systems, the electricity is used to compress air in compressors, generating high levels of heat during the process. The heat of the compressed air is removed at the outlets of the compressors and stored in a thermal energy storage (TES) unit, while the cool compressed air is stored in a cavern at depths of hundreds of metres. To discharge the energy on demand, the cool compressed air heats up in the TES before expansion in turbines to generate electricity. Despite its promising features for decarbonising the electricity power system, there are major challenges which hinder further development of ACAES systems, including (1) limitations on the underground geology, (2) low roundtrip efficiency and (3) thermal and structural challenges on the TES unit because of high-temperature air at the outlets of the compressors. This proposal aims to address these major challenges through development of an affordable micro-scale co-generation near-isothermal and adiabatic CAES system with overground air storage vessels (micro-Ni-ACAES). The system utilizes near-isothermal and high-efficiency compressor/expander devices, TES and heat exchanger units based on an innovative composite phase change material and air storage vessels. The project will perform a fundamental experimental and modelling analyses to gain deep insight into the flow and thermal fields in the near-isothermal compressors/expanders as well as charging and discharging kinetics of the TES unit. Both isochoric and isobaric storage processes will be analysed. These fundamental studies will lead to efficient designs of the micro-Ni-ACAES system components and further support the development of a thermodynamics-based design tool. The design tool will be used to identify the system's optimum operating condition and control strategy for steady-state and dynamic operations of the system. Additionally, the project will include a techno-economic and environmental impact assessment in order to evaluate the economic viability of the system, as well as CO2 abatement and fossil fuel savings over the system's lifetime. The proposed high efficiency co-generation micro-Ni-ACAES systems are believed to be the future of the CAES technology, eventually culminating in decentralised microgrid power network in application to district energy network or commercial sectors (e.g. business parks).

The Phanerozoic Eon (the last 540 million years) encompasses the evolutionary history of land plants from the initial colonization of the land through to forests and flowering plants. Earth's climate has undergone major changes over this timeframe, but it remains uncertain whether these changes were primarily driven by revolutions in the terrestrial biosphere, or by tectonic factors such as volcanic degassing of CO2. Resolution of this question lies at the heart of our understanding of how our planet operates, but the ability to answer it has been hampered by a lack of representation of the terrestrial biosphere in our biogeochemical computer models. These 'deep-time' models need to be simple in order to compute very long timescales, and this limits the ability to include spatial features such as locations of rainfall, which are vital to terrestrial modelling. A perhaps more fundamental problem is the lack of understanding of the way that plant evolution has altered global chemical cycling through changes to carbon-nitrogen-phosphorus ratios in tissue, and what the contribution of fungal and microbial symbionts were to supplying key limiting nutrients. This project brings together expertise in computer science, geochemistry, ecology and plant-symbiont physiology to build a new deep-time spatial Earth system model, informed by a targeted suite of plant growth experiments and a robust literature review. Firstly, we will run laboratory experiments with early diverging plants and symbiotic nitrogen-fixing trees, with and without partnership with fungal and/or nitrogen-fixing symbionts in microcosms with controlled atmospheric CO2 concentrations. Introduction of isotopically-labeled carbon, nitrogen and phosphorus will allow us to capture the carbon-nitrogen-phosphorus stoichiometric ratios and nutrient acquisition pathways for diverse plant-symbiont partnerships across the plant phylogeny, filling significant gaps in current knowledge of these processes. These experiments will allow us to understand: a. Plant-symbiont carbon-nutrient "costs" and "benefits" in terms of plant-fixed carbon and symbiont-acquired nutrient gains b. How ecological stoichiometry and nutrient acquisition pathways vary across the land plant phylogeny c. Relationships between species, symbiont and mineral weathering rates Second, we will develop our new Earth system model. Here we will build on the framework of the 'COPSE' model (Carbon Oxygen Phosphorus Sulphur Evolution), which is arguably the most complete predictive 'deep time' box model in the literature, and which PI Mills has had a key role in developing over the last decade. A prototype fast spatial land surface module has been developed utilizing matrices in MATLAB and in this project we will couple the spatial land surface module to COPSE. This will allow us to build a dynamical representation of the evolving terrestrial biosphere, based both on our laboratory experiments and on literature vegetation models. This model will map the flows of phosphorus, nitrogen and carbon through the terrestrial system over geological timescales. Comparison of model outputs with multiple independent geochemical proxies will allow us to explore (1) how plant evolution and the development of symbiotic partnerships feeds back on Earth's climate; (2) the key evolutionary events that occurred through time and whether they can explain prominent CO2 drawdown events, such as during the Ordovician and Cenozoic; and, (3) the relative roles of the terrestrial biosphere vs. tectonics in controlling Earth's climatic history. Beyond the immediate results, the hybrid model we create will bridge the gap between box modelling of global geochemistry and true paleoclimate general circulation modelling, providing a useful tool for the community to further extend and employ.

The successes of nanoscale magnetism and spintronics (where the spin of the electron is manipulated) have been enabling for materials-by-design magnetism. However, these accomplishments have placed ever more emphasis on precisely controlling the transportation of electron spin. This is nowhere more critically seen than in the case of hard disk drive read heads, where continued reduction in read head size places serious limits to the future use of tunnel magneto-resistance sensors - a major challenge for the ICT industry. Low impedance alternatives are now actively sought, with all-metallic devices returning to the forefront of interest. Remarkably, despite the ubiquity of spintronic devices like read heads, there remain stark gaps in our understanding of spin transport in metallic systems at the nanoscale. Even in the (relatively) simple ferromagnetic and non-magnetic materials used in magnetoresistive devices, recent results have called into question our understanding at this level. This imposes a number of substantial challenges for their future use. Moving beyond these materials even less is known and, in general, the wider interplay between precise electronic phase and spin transport is only beginning to be probed. The impact of such limitations to current technology is readily seen, with the vast majority of spintronic devices limited to considering only the manipulation of long-range ferromagnetic materials, e.g. in storage applications. Indeed, the possibility of controlling state with spin, beyond ferromagnetic switching, could bring entirely new functionality to spintronic devices, potentially leading to transformative new technologies -- an exciting prospect. The aim of this proposal is to explore mediating phase transitions using pure spin currents. We will first explore pure spin transport, using a device known as a 'non-local spin valve' as a research platform to incorporate complex magnetic materials. Initially this will involve tailoring spin channel properties to systematically bring to light the role of specific defects in limiting spin transport -- crucial results for enhancing spin signals in metallic devices. We will then move to understand the interplay between electronic phase and spin diffusion, attempting to probe spin transport across a host of fundamental phase transitions, including spin glass freezing, metallic to insulating and ferro- to antiferro-magnetic. By doing so, a wealth of new information on the interaction of spin currents with phase will be revealed. Through a number of spin generation techniques, we will examine the role of the torques from absorbed spin currents in stabilising phases, enhancing critical temperatures, moving phase boundaries and inducing critical fluctuations across a host of these transitions. By using the NLSV for these studies, we will be able to explore such effects in a novel but technologically relevant environment.

Chlorophyte "snow algae" and Streptophyte "glacier algae" are found across the cryosphere, forming widespread algal blooms in snowpacks and on glacier ice surfaces during spring/summer melt seasons. These blooms hold significant potential to exacerbate the already rapid loss of snowpack and glacial ice resources driven by climate change because they establish albedo feedbacks that amplify melt. Their presence also leads to the construction of active microbial food-webs that provide important ecosystem functions, e.g. carbon sequestration, nutrient cycling and export of resources to down-steam systems. The algae themselves are also important analogs for what life was like on Earth during past mass glaciations, and for how life may exist on other frozen planets across our solar system. Driven by these series of novelties, the snow and glacier algal research community has significantly expanded over recent years, with active projects now spanning Arctic, Alpine and Antarctic regions of the cryosphere. To-date, however, research projects have tended to work in isolation, employing different methods for the analysis of blooms. This has prevented comparisons of findings between regions of the cryosphere and an overall appreciation for the global role and impacts of blooms at present. In turn, we cannot yet project the fate of snow and glacier algal blooms into the future under climate change, or back to the past during key periods of Earth's history. Yet the critical mass achieved in the snow and glacier algal research community also presents an opportunity to pool knowledge and resources, and align methods to drive the field to new achievements. The CASP-ICE project brings together leaders in the field of snow and glacier algal research (x2 UK investigators and x12 international partners) to undertake the foundational work needed to align efforts across the research community and unlock the next generation of science on snow and glacier algal blooms cryosphere-wide. Specifically, we will tackle the following four major tasks: 1. Define consistent methods for sampling and mapping snow and glacier algal blooms within field sites, so that datasets produced into the future will be completely comparable across different regions and times of sampling. 2. Apply these methods in study sites that the CASP-ICE team are currently working to produce the first set of standardized samples and maps of blooms for the community to work with. 3. Undertake the nuts-and-bolts validation of both laboratory-based methods for analyzing field samples as well as computational methods for integrating field measurements and mapping datasets with larger-scale satellite imagery that is needed to monitor blooms at global scales. 4. Establish a list of field sites that can form the backbone of an ongoing cryospheric algal bloom monitoring network and secure the funding to continue monitoring into the future. CASP-ICE will achieve these tasks through a series of networking and knowledge exchange activities as well as hands-on science. An initial workshop in spring 2024 will provide the platform to define best practice methods for the community and start talks on future network structure and direction. All partners will then undertake sampling and sample/data analysis across their respective study regions to produce the first fully validated datasets on snow and glacier algal blooms across the cryosphere. The protocols defined and datasets produced will be leveraged in subsequent funding bids that will be prepared during a series of networking visits and partner meetings led by the project PI, providing the support needed for ongoing monitoring of blooms into the future as climate change proceeds. CASP-ICE will provide the network and scientific foundation needed to tackle the large-scale questions about the role of cryospheric algal blooms in the Earth System at present, into the future under climate change, and back into the past.