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Author(s): Johannes Gebhard, Peter Hilz, Felix Balling, Joey Kalis, Martin Speicher, Leonard Doyle, Alexander Sävert, Georg Schäfer, Pooyan Khademi, Bin Liu, Matt Zepf, and Jörg Schreiber

Isolated micro-targets are a promising avenue to high-performance laser-driven proton and ion accelerators due to their ability to confine the coupled laser energy to a small volume and small number of particles. Experimental results on proton emission from levitated plastic micro-spheres with an in…

[Phys. Rev. E 112, 035204] Published Tue Sep 09, 2025

Author(s): Wang-Wen Xu, Zhang-Hu Hu, Hao-Yuan Li, Jie-Jie Lan, and You-Nian Wang

We report in this work the current filamentation instability of laser-produced proton beams in a regime where the plasma collision frequency is much smaller than the plasma oscillation frequency but larger than the growth rate of the instability. In this regime, the plasma electron temperature incre…

[Phys. Rev. E 112, 035205] Published Tue Sep 09, 2025

Five well-publicized polar geoengineering ideas are highly unlikely to help the polar regions and could harm ecosystems, communities, international relations, and our chances of reaching net zero by 2050.

SummaryThe stratification stability in the Earth's fluid outer core, which is challenging to constrain with seismology, could potentially be revealed by core undertones (typical inertial-gravity waves). Radial motions from internal inertial-gravity waves are believed to induce minuscule gravity variations at the Earth's surface, yet no conclusive observational evidence has been reported. In this study, we present a systematic search for core undertones within two intertidal bands by stacking a global dataset of superconducting gravimeter observations, comprising 59 gravity residual sequences from 42 stations between July 1, 1997 and February 29, 2024. Under the hypotheses of seismic excitation and sustained excitation, the optimal sequence estimation is used to retrieve spatially coherent signals associated with low-degree (l ≤ 4) spherical harmonic patterns; the z-domain autoregressive power spectrum is used to highlight the weakly damped harmonic signal against the background noise. Rigorous statistical significance analyses indicate that seismic events are insufficient to excite core undertones to the currently observable level. Assuming that core undertones are sustainably excited, we identify three candidate undertones with periods of 9.93, 9.73, and 9.51 hours, associated with spherical harmonic patterns Y2,+1, Y2,–2, and Y3,+2, respectively, which suggest that the liquid outer core near the core surface may contain a strongly stabilized layer characterized by a relatively higher buoyancy frequency. The findings may contribute new insights into the structure and dynamics of the Earth's deep interior as inferred from surface gravimetry.

A new study has uncovered the Levant Basin as one of the world's most concentrated graveyards for plastic packaging and the mechanisms that help the plastic sink down to the seafloor.

Antarctic ice is melting. But exactly which forces are causing it to melt and how melting will influence sea level rise are areas of active research. Understanding the decay of ice shelves, which extend off the edges of the continent, is particularly pressing because these shelves act as barriers between ocean water and land. Without ice shelves, the continent's glaciers would flow freely into the ocean, hastening sea level rise.

The United States could consume the added-sugar equivalent of as much as 7 billion additional cans of soda per year by 2095 as a result of climate change, according to a new study. 

A new analysis of food consumption patterns and weather data in the country, published in Nature Climate Change, showed that warmer temperatures increase household purchases of food and beverage products with added sugar, especially among low-income and less educated populations. 

“There’s a huge difference across different socioeconomic groups.”

“There’s a huge difference across different socioeconomic groups,” said Duo Chan, a climate scientist at the University of Southampton and coauthor on the new study. 

Researchers analyzed retail food and drink purchases in more than 40,000 U.S. households from 2004 to 2019 along with monthly average temperatures at the county scale. They found that the average adult male purchased about 0.70 gram of additional added sugar per day for every additional 1°C (1.8°F) of temperature between 12°C (53.6°F) and 30°C (86°F).

Researchers ran multiple regression analyses to rule out other factors that could have influenced the purchasing of sugary products. With the effects of other variables, such as changes in product price, removed, added-sugar intake remained significantly associated with temperature, Chan said.

“It’s the change in temperature that [leads] to the sugar intake,” said Pengfei Liu, an environmental economist at the University of Rhode Island and coauthor of the new study.

The trends, according to the authors, are probably driven by people choosing hydrating, sweet beverages and cold desserts to mitigate the effects of heat. The patterns are “common sense,” said Thalia Sparling, a public health researcher at the London School of Hygiene & Tropical Medicine who was not involved in the new research. “Of course, when it gets hotter, you’re going to want to sit on the porch with your friends and have a cold drink or eat more ice cream.”

Education and income levels of the heads of households influenced how sensitive those households’ sugar consumption patterns were to increases in temperature. Households in which the head of household had a lower income and was less educated increased their added sugar purchases more per degree of increased temperature. Purchases of sweetened beverages and frozen desserts constituted the bulk of the increased sugary purchases.

The study authors used Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models to project that warming temperatures in a high-emissions world could change diets enough to add nearly 3 grams of sugar per day to the average U.S. diet by the end of the century—equivalent to about 30 cans of soda per person per year. The projected effects were unequal among socioeconomic groups, too, with lower-income and less educated households expected to increase their sugar intake more than their higher-income, more educated counterparts. 

Dietary Inequality

“This is just another piece of evidence showing that the impacts of climate change on people are not equal.”

“This is just another piece of evidence showing that the impacts of climate change on people are not equal,” Sparling said.

Nutrition researchers have long known that lower-income groups eat less healthily, Sparling said, because of economic factors, lack of access to healthier foods, and even work environment. “People in communities with lower average [socioeconomic status] are less likely to have air-conditioned workplaces, schools, homes, or respite in other ways,” she said. Those without a way to escape the heat may be more likely to reach for cold, sweetened drinks or desserts for relief.

“Low-income people are most vulnerable to climate change in a lot of cases, and also in our case, in terms of excessive sugar intake,” Chan said. 

Higher added-sugar consumption can increase the risk of various health problems such as obesity, diabetes, and heart disease. But because the causes behind health problems are so complex, much more research would be needed to link warming to specific increases in disease, Sparling said.

She stressed that the onus to improve dietary choices should not be all on the individual: “You have to look at systems level change,” she said. Policies such as taxes on sweetened beverages have decreased added sugar consumption in some cities and countries. Education in communities, schools, and churches can also help people form healthier habits, Sparling said. 

More research is needed to determine whether the trends seen in the United States are reflected across the globe, said Pan He, an environmental social scientist at Cardiff University and first author of the new study. Then, scientists could have an even more comprehensive understanding of how global food consumption patterns may adapt to climate change, she said. 

“I hope our study may shed light on future evidence in developing countries, where sugary-beverage intake is already high and rising heat could further threaten nutrition security,” wrote Yan Bai, an economist at the World Bank and coauthor of the new study, in an email.

—Grace van Deelen (@gvd.bsky.social), Staff Writer

Citation: van Deelen, G. (2025), Heat spurs unequal consumption of sweet treats, Eos, 106, https://doi.org/10.1029/2025EO250333. Published on 8 September 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Scientists have confirmed that East Antarctica's interior is warming faster than its coastal areas and identified the cause. A 30-year study, published in Nature Communications and led by Nagoya University's Naoyuki Kurita, has traced this warming to increased warm air flow triggered by temperature changes in the Southern Indian Ocean.

Imagine a farmer standing in her field—or even sitting at home—when she gets an alert from a handheld device: Her crops are showing signs of stress, not from heat, drought, or lack of nutrients in this case, but from a pesticide spill detected upstream. The alert doesn’t come from a lab test conducted days after the initial contamination. Instead, it is generated in real time by a portable biosensor containing a protein derived from a pig’s nose.

Chemical-sniffing sensors, though not yet widely adopted in agriculture or environmental science, represent an emerging field of research and development.

The protein has been reprogrammed to mimic the molecular recognition capabilities of animal olfaction, allowing it to detect specific volatile chemicals associated with pesticide contamination and enabling rapid on-site detection. With this early warning, the farmer can act swiftly to mitigate negative impacts and protect both her crops and future yield.

Chemical-sniffing sensors like this, though not yet widely adopted in agriculture or environmental science, represent an emerging field of research and development. They also offer viable new tools for addressing urgent 21st century environmental challenges related to climate change, rapid industrialization, urban sprawl, deforestation, and agricultural intensification, which threaten biodiversity, food security, and public health globally.

In response to these challenges, the United Nations’ Sustainable Development Goals (SDGs)—particularly SDG 6 (Clean Water and Sanitation), SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), SDG 14 (Life Below Water), and SDG 15 (Life on Land)—call for integrated, data-driven approaches to environmental monitoring and management that support environmentally, economically, and socially responsible practices.

Implementing these goals, especially in remote regions and developing nations, requires affordable, scalable methods for monitoring air, water, and soil resources that deliver timely and actionable information. Naturally occurring animal proteins, paired with biosensing technology, offer a promising foundation.

A Transformative New Approach

Detecting pollutants in air, water, or soil often requires sending samples to distant laboratories for gas chromatography, mass spectrometry, or other high-precision analyses. These tools are indispensable for regulatory science because they deliver highly accurate, standardized measurements of trace contaminants that can withstand legal and policy scrutiny. However, the time required to collect, ship, and analyze samples delays results and limits their usefulness for rapid, local decisionmaking.

Conventional in situ monitoring systems, such as stationary air- and water-quality stations, provide continuous data but are expensive to install and maintain. As a result, they are typically sparsely distributed, provide limited spatial coverage, and require significant power, connectivity, and upkeep. Together the high costs and infrastructure demands of current methods make them impractical for widespread field deployment, especially in remote, resource-limited, or rapidly changing environments.

Biosensors present a viable, transformative alternative. Compact, energy-efficient, and often portable, these devices combine biological recognition elements, such as enzymes, antibodies, or odorant-binding proteins (OBPs), with signal transducers to detect specific compounds on-site, in real time, and at low cost. Notably, these devices can sense volatile chemicals and bioavailable pollutant fractions, making them well-suited to complement or even replace traditional environmental monitoring tools in certain settings.

Fig. 1. The structure of a porcine odorant-binding protein (pOBP) is shown by this ribbon diagram. A molecule of butanal, a volatile organic compound used in industrial manufacturing applications, is depicted within the binding cavity of the protein. Credit: Cennamo et al. [2015], CC BY 4.0

OBPs, a class of tiny but mighty proteins found in the olfactory systems of insects and vertebrates, are especially appealing options (Figure 1). They detect trace amounts of odorants—the molecules behind scents—in complex, chemically noisy environments. Whether it is a moth navigating miles to find a mate, or a mammal sniffing out food, OBPs enable detection of a few key molecules amid thousands.

Today researchers are repurposing OBPs to sniff out the chemical by-products of modern life. These proteins possess high thermal and chemical stability, are easy to synthesize, and are remarkably versatile. They can be integrated into portable devices and miniaturized sensors, affixed to biodegradable materials, and genetically engineered to target specific chemicals in soil, air, or water.

OBPs in Action

Despite their promise, biosensors remain underrepresented in discourse and planning related to environmental monitoring and sustainability. More often than not, prototypes developed and tested in the laboratories fail to reach broad application in the field. Specific uses of OBPs have remained largely siloed within biomedical and entomological research.

However, emerging applications of OBPs align closely with key geoscience priorities, including tracking pesticide and industrial runoff, monitoring volatile compounds and mapping soil emissions, and identifying plant health indicators tied to environmental stress and drought. Several proof-of-concept and real-world demonstrations are already underway, highlighting how OBPs can detect a range of pollutants across different environments.

Fig. 2. These prototype biosensors (top), with the gold-plated sensing area at the far left of each, were designed to detect benzene in the environment. The diagram (bottom) illustrates the process by which the sensing surface was chemically functionalized with pOBP (pink ribbon diagram). Credit: Capo et al. [2022], CC BY 4.0

Porcine OBPs have been engineered to detect BTEX pollutants (benzene, toluene, ethylbenzene, and xylene) originating from pesticides and petroleum runoff that threaten groundwater and soil health (Figure 2) [Capo et al., 2022, 2018]. Bovine OBPs, immobilized on cartridge-like devices, can selectively bind and remove triazine herbicides from water, demonstrating potential for both detection and remediation of the pollutant in water treatment [Bianchi et al., 2013].

Sensors coated with bovine and porcine OBPs detect trace, mold-related volatile organic compounds (VOCs) such as octenol and carvone [Di Pietrantonio et al., 2015, 2013], which is relevant to both indoor and outdoor air quality monitoring and mitigation of post-harvest crop losses. Low-cost, OBP-functionalized devices have also demonstrated selective detection of butanal, a common VOC linked to industrial and urban particulate matter [Cennamo et al., 2015].

In addition to bovine and porcine OBPs, rat OBP derivatives have been customized and immobilized on sensing platforms to enable simultaneous VOC profiling for air and water pollution diagnostics [Hurot et al., 2019]. Furthermore, insect OBPs, embedded in fluorescence-based biosensors, have shown efficacy for detecting bacterial metabolite, offering a possible approach for rapid coliform bacteria screening in drinking water [Dimitratos et al., 2019].

Beyond environmental and water quality applications, OBPs from multiple species have also been used to monitor for plant-emitted VOCs that signal stress, disease, drought, or pest infestation in agricultural systems [Wilson, 2013], providing valuable insights into crop health and enabling early intervention strategies.

The Potential Is Enormous

Integrating OBPs into environmental monitoring systems opens new frontiers in climate-smart agriculture, distributed sensing networks, and adaptive land use management.

Integrating OBPs into environmental monitoring systems opens new frontiers in climate-smart agriculture, distributed sensing networks, and adaptive land use management. These sensors offer lab-grade sensing of emissions from sources such as livestock waste, fertilizer application, and wetland activity. They may also enable real-time monitoring of greenhouse gas precursors and early detection of soil degradation, microbial shifts, or drought stress—all delivered through devices small enough to fit in your pocket.

Early detection of pollutant leaks or VOC hot spots could inform land use strategies that mitigate volatile emissions, improve air quality, and strengthen climate adaptation. OBP sensors’ low power requirements and biodegradability make them ideal for decentralized deployments, especially in low-resource or remote areas. Engineered differently, these proteins could even serve in preventative technologies as molecular sponges or scavengers that capture and bind VOCs before they accumulate or disperse.

Ultimately, OBPs could enable more data-driven decisions in conservation and climate policy, while offering novel tools for mapping environmental dynamics (e.g., tracking the spread of wildfire smoke plumes, monitoring methane emissions, or detecting waterborne coliforms across river networks) at finer spatial and temporal resolutions than current technologies permit.

From the Bench to the Biosphere

We envision a future in which OBPs are central to smart agriculture platforms, mobile environmental sensing labs, and biodegradable field-deployable kits. The underlying technology is sound, but breakthroughs like this don’t happen in isolation. Cross-disciplinary collaboration is crucial to accelerate and scale this development, reduce risks of field deployments, and ensure that innovations are aligned with real-world policy and practice.

We propose several pathways to support this collaboration and innovation. For example, targeted workshops and research consortia could facilitate dialogue among molecular biologists, environmental engineers, and Earth scientists to identify priority research questions and focus efforts on specific environmental challenges.

Key questions for advancing OBP-based sensing include the following: Which pollutants and ecosystem signals are most critical for understanding today’s environmental challenges? How can OBPs be tuned to target specific compounds under varying soil, air, or water conditions? What substrates can effectively host OBPs for real-world sensing without compromising environmental safety?

As part of this dialogue, environmental scientists could contribute by generating regional maps of priority VOCs linked to specific issues such as crop stress, emissions from peatlands, or urban air pollutants, guiding optimization of OBP-based sensors. Similarly, chemists and bioengineers could collaborate to expand the library of OBPs with tailored affinities for emerging pollutants, such as pharmaceutical residues, industrial solvents, or novel agrochemicals, broadening the range of compounds detectable in real-world settings. In parallel, data scientists and systems engineers could develop machine learning models to decode complex VOC signatures captured by OBP sensors, enabling real-time diagnostics, pattern recognition, and predictive analytics across environmental monitoring networks.

Expanding access to knowledge and resources represents another key pathway for advancing OBP-based sensing.

Expanding access to knowledge and resources represents another key pathway for advancing OBP-based sensing. Developing curated, open-source, and searchable repositories of OBPs from diverse organisms with characterized binding affinities for high-priority VOCs would accelerate biosensor design and prototyping. Such repositories should follow FAIR (Findable, Accessible, Interoperable, Reusable) data principles to maximize their usefulness across disciplines and platforms.

In the United States, agencies such as the National Science Foundation, the Department of Agriculture, EPA, and the Department of Energy could accelerate progress by hosting seed funding workshops to define shared goals, barriers, and applications and by providing joint funding for interdisciplinary biosensing projects.

Establishing and sharing experimental field test beds such as smart farms, urban air zones, and wetlands would enable pilot testing of OBP-based sensors alongside conventional instruments. These biosensors could be integrated into existing monitoring networks like the National Ecological Observatory Network and the Long Term Ecological Research Network. Their outputs could feed into land use, emissions, and ecological models to improve the spatiotemporal resolution of environmental data.

Building on these test beds and integrated networks, collaborating researchers could report cross-disciplinary benchmark studies and coauthor seminal papers detailing protocols, use cases, and best practices for OBP-based biosensing. This coordinated effort would guide future research and help establish the field’s credibility with regulators and funding agencies.

Clearing Barriers on the Road Ahead

For all of the upsides of OBP-based biosensing, several technical and logistical issues must be addressed before their widespread deployment is achieved.

Despite their superior stability compared to enzymes or typical antibodies [Dimitratos et al., 2019], OBPs remain susceptible to denaturation or degradation during prolonged environmental exposure. Environmental conditions such as humidity, pH, and salinity can affect their performance, underscoring the need for robust protocols to stabilize and calibrate these proteins across diverse ecosystems.

Advancing real-time data acquisition and remote monitoring with OBP-based biosensing also requires progress toward integrating the proteins with digital platforms in scalable and reproducible formats. Key challenges include reducing sensor-to-sensor variability, increasing sensor lifespans, and converting biological signals into stable, digitized outputs.

Realizing the technology’s broader potential will require rigorous technical validation, clear regulatory guidance, and proactive efforts to educate and engage stakeholders.

In addition to technical barriers, regulatory frameworks and approval pathways for OBP-based sensing technology remain underdeveloped, and concerns about the lack of standardized validation protocols and the effects of releasing recombinant proteins into agricultural or environmental settings persist. Moreover, low awareness among end users, including farmers and land managers, may hinder trust and uptake of the technology. Realizing its broader potential will thus require rigorous technical validation, clear regulatory guidance, and proactive efforts to educate and engage stakeholders across sectors. Notwithstanding these challenges, the promise is clear: OBPs offer a flexible and powerful approach for monitoring environmental changes and climate risk, helping to protect ecosystems, food systems, and communities. Once known primarily to entomologists, these little scent-sniffing proteins could become an unexpectedly powerful tool for advancing environmental resilience.

References

Bianchi, F., et al. (2013), An innovative bovine odorant binding protein-based filtering cartridge for the removal of triazine herbicides from water, Anal. Bioanal. Chem., 405, 1,067–1,075, https://doi.org/10.1007/s00216-012-6499-0.

Capo, A., et al. (2018), The porcine odorant-binding protein as molecular probe for benzene detection, PLOS One, 13(9), e0202630, https://doi.org/10.1371/journal.pone.0202630.

Capo, A., et al. (2022), The porcine odorant-binding protein as a probe for an impedenziometric-based detection of benzene in the environment, Int. J. Mol. Sci., 23(7), 4039, https://doi.org/10.3390/ijms23074039.

Cennamo, N., et al. (2015), Easy to use plastic optical fiber–based biosensor for detection of butanal, PLOS One, 10(3), e0116770, https://doi.org/10.1371/journal.pone.0116770.

Dimitratos, S. D., et al. (2019), Biosensors to monitor water quality utilizing insect odorant-binding proteins as detector elements, Biosensors, 9(2), 62, https://doi.org/10.3390/bios9020062.

Di Pietrantonio, F., et al. (2013), Detection of odorant molecules via surface acoustic wave biosensor array based on odorant-binding proteins, Biosensors Bioelectron., 41, 328–334, https://doi.org/10.1016/j.bios.2012.08.046.

Di Pietrantonio, F., et al. (2015), A surface acoustic wave bio-electronic nose for detection of volatile odorant molecules, Biosensors Bioelectron., 67, 516–523, https://doi.org/10.1016/j.bios.2014.09.027.

Hurot, C., et al. (2019), Highly sensitive olfactory biosensors for the detection of volatile organic compounds by surface plasmon resonance imaging, Biosensors Bioelectron., 123, 230–236, https://doi.org/10.1016/j.bios.2018.08.072.

Wilson, A. D. (2013), Diverse applications of electronic-nose technologies in agriculture and forestry, Sensors, 13(2), 2,295–2,348, https://doi.org/10.3390/s130202295.

Author Information

Ishani Ray (isray@okstate.edu) and Smita Mohanty, Department of Chemistry, Oklahoma State University, Stillwater

Citation: Ray, I., and S. Mohanty (2025), Protein-powered biosensors with a nose for environmental ills, Eos, 106, https://doi.org/10.1029/2025EO250330. Published on 8 September 2025. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 2025. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Source: Journal of Geophysical Research: Oceans

Antarctic ice is melting. But exactly which forces are causing it to melt and how melting will influence sea level rise are areas of active research. Understanding the decay of ice shelves, which extend off the edges of the continent, is particularly pressing because these shelves act as barriers between ocean water and land. Without ice shelves, the continent’s glaciers would flow freely into the ocean, hastening sea level rise.

In January 2015, a group of researchers used hot water to drill a hole through 740 meters of the Ronne Ice Shelf. They then lowered a mooring carrying temperature, salinity, and current sensors through the hole into the ocean below. A radio echo sounder deployed 15 meters from the mooring kept tabs on ice thickness. For the next 3 years, the instruments took measurements every 2 hours; these measurements were sent to a solar-powered data logger on the surface and then on to researchers via satellite.

Anselin et al. recently used these measurements to probe the forces responsible for melting ice shelves.

The tide is a major force contributing to ice shelf melting, the researchers found. As the tide rises, the water rushes across the bottom of the shelf. Friction between the shelf and the water causes the current just beneath the ice to slow. This slowdown leads to strong mixing within the ocean, and this mixing brings heat to the ice base, driving high melt rates. Because the strength of tides varies depending on the positions of the Sun and the Moon relative to Earth, ice shelf melting has a cyclical pattern, with melting ebbing and flowing every 2 weeks.

However, current models of melt rates fail to capture the full extent to which tidal mixing and warm ocean water combine to melt ice. When analyzing data from additional sites, scientists should focus on how the interaction between tides and ice shelves leads to melting, the researchers say. (Journal of Geophysical Research: Oceans, https://doi.org/10.1029/2025JC022524, 2025)

—Saima May Sidik (@saimamay.bsky.social), Science Writer

Citation: Sidik, S. M. (2025), Strong tides speed melting of Antarctic ice shelves, Eos, 106, https://doi.org/10.1029/2025EO250331. Published on 8 September 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

A common problem with oil wells is that they can run dry even when sound-based measurements say there's still oil there. A team from Penn State University used Pittsburgh Supercomputing Center's (PSC's) flagship Bridges-2 supercomputer to add a time dimension to these seismic measurements, as well as to analyze how oil damps down the loudness of sound traveling through it. Their preliminary analysis suggests that hidden rock structures in oil reserves prevent all the oil from being pumped out. They're now scaling up their work to tackle realistically sized oil fields.

Resilience is a term often discussed in the face of a natural disaster such as a major earthquake, but the attributes of resilience and how they interact are rarely analyzed, researchers say in a new study published in the Bulletin of the Seismological Society of America.

Author(s): Tobias Dornheim, Thomas M. Chuna, Hannah M. Bellenbaum, Zhandos A. Moldabekov, Panagiotis Tolias, and Jan Vorberger

Spherically averaged periodic pair potentials offer the enticing promise to provide accurate results at a drastically reduced computational cost compared to the traditional Ewald sum. In this work, we employ the pair potential by Yakub and Ronchi [J. Chem. Phys. 119, 11556 (2003)] in ab initio path …

[Phys. Rev. E 112, 035203] Published Mon Sep 08, 2025

SummaryExpanding the lower-frequency band of seismic energy sources, particularly below 2.0 Hz, is crucial for improving the stability and effectiveness of full waveform inversion (FWI). Conventional active sources including airguns are ineffective at generating low-frequency wavefields, while ambient seismic wavefields, driven by natural energy sources such as ocean waves, offer a promising alternative. Effectively using ambient wavefield energy for seismic imaging or inversion analyses, though, requires understanding key physical control factors contributing to observations - including ambient source mechanisms and distribution, ocean-bottom bathymetry, and Earth model heterogeneity - which influence wave-mode excitation and partitioning, particularly in the context of ocean-bottom ambient seismology interferometry. This study presents a modeling framework for simulating cross-correlation wavefields generated by ambient seismic sources for dense ocean-bottom sensor arrays within a coupled acoustic-elastic system, without relying on Green’s function retrieval assumptions. We model velocity and pressure cross-correlation wavefields to explore the effects of ocean-bottom velocity structure, ambient source distributions, and bathymetric variations on seismic wave excitation and propagation in the low (0.01-2.00 Hz) frequency band. Our results show that the distribution of ambient energy source locations, whether at the seabed or sea surface, significantly affects excited wave-mode characteristics. Love waves are particularly evident in the presence of substantial lateral and vertical bathymetric variations and heterogeneous Earth structure. The distribution of azimuthal ambient energy sources also influences Love-wave excitation, with the most prominent waves observed in the direction of the highest source concentration. Additionally, different particle velocity component and pressure virtual shot gathers exhibit varying sensitivity to surface waves. This work improves the understanding of low-frequency ambient seismic wavefields in ocean environments, with potential applications in long-wavelength structural imaging and elastic velocity model estimation from FWI analysis.

SummaryPredicting seafloor topography (ST) from altimetry-derived gravity data is an effective method for obtaining ST in sea areas with sparse bathymetry. Classical ST inversion methods primarily utilize gravity anomaly, whereas vertical deflection (VD)—a fundamental product of altimetry that exhibits greater sensitivity to high-frequency ST is infrequently employed. We propose an iterative method for optimization to predict ST using VD in the spatial domain, which addresses the major problem—high nonlinearity between VD and ST. It considers the Airy-isostatic compensation and removes the non-topographic components while preserving short-wavelength signals. Our method predicts the optimal ST by iteratively minimizing the squared 2-norm of the weighted residual vector between the forward-modelled and observed VD. A synthetic test conducted in a part of the South China Sea preliminarily validates the method’s effectiveness. A real-data experiment in the Arctic Ocean shows that the root-mean-square (RMS) of differences between the ST_VD model constructed using our method and checkpoints is 110.43 m, representing improvements of 6.45, 18.85, and 13.95 per cent over the topo_27.1, ETOPO1, and IBCAO V3, respectively. Accuracy verification in different depth ranges and profile analysis indicate that ST_VD exhibits significant advantages in shallow depth (≤2,000 m), while it is relatively inferior in deep depth (>2,000 m). Radial power spectra reveal that ST_VD possesses higher energy at short wavelengths (less than ∼10 km), and its energy at intermediate-long wavelengths is consistent with the comparison models. The results demonstrate our method can effectively recover detailed ST in shallow areas and enhance the short-wavelength ST.

SummaryMagnetite-apatite (MtAp) deposits have attracted considerable attention due to their complex genesis and economic importance. These deposits are rich in magnetite ore and can bear significant rare-earth elements, but their exact formation mechanisms remain controversial. This study aims to understand the formation processes of MtAp deposits by investigating the role of iron-rich magmatic liquids. Focusing on the El Laco deposit, northern Chile, we follow the hypothesis that iron-rich liquids separate from silicate magma through liquid immiscibility. Building on previous research, this study employs a three-phase one-dimensional (1D) mechanical model to simulate the separation and accumulation of immiscible iron-rich melts within increasingly crystalline magma. The model reproduces the previously suggested transition from isolated droplet settling to an interconnected drainage network and quantifies the relative efficiency of both modes of phase separation. Using scaling analysis, we define porous, mush, and suspension flow regimes and construct a regime diagram for three-phase flow. The results indicate that the separation efficiency of immiscible iron-rich melts is maximised in the mush flow regime at intermediate crystallinity. The model-derived accumulation rate of iron-rich melts can be used to estimate the time required to form magnetite deposits of a given scale. Our findings support the physical viability of the liquid immiscibility hypothesis for the genesis of MtAp deposits, offering new insights into the mechanical efficiency of melt separation and contributing to a broader understanding of the formation mechanisms of other valuable deposits that have been linked to immiscible melts.

Publication date: 1 November 2025

Source: Earth and Planetary Science Letters, Volume 669

Author(s):

Publication date: 1 November 2025

Source: Earth and Planetary Science Letters, Volume 669

Author(s): Jiliang Wang, Ang Li, Wei Zhang, Jin Sun, Jiecheng Zhang, Xueqing Zhou, Shiguo Wu

Publication date: 1 November 2025

Source: Earth and Planetary Science Letters, Volume 669

Author(s): Weijia Sun, Hrvoje Tkalčić, Marco G. Malusà, Ludmila Adam, Qingya Tang, Sheng Wang, Zhi Wei, Yongxin Pan

Publication date: 1 November 2025

Source: Earth and Planetary Science Letters, Volume 669

Author(s): Peter Methley, Clancy Z. Jiang, Justin V. Strauss, Nicholas J. Tosca