EOS

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Journal of Geophysical Research: Space Physics

Earth is surrounded by rings of energetic particles called radiation belts. The inner belt can sometimes be populated by megaelectron volt (MeV) energetic electrons during particularly strong solar storms. When moved by electromagnetic waves, these energetic particles can rain into the atmosphere.

Feinland and Blum [2025] show that periodic signatures of relativistic electron rain observed by satellites can be used to better predict when and where they might happen in the future. The authors find that these high-energy electrons usually came into the inner belt quickly after solar storms and gradually rained out over the course of a few weeks. During particularly quiet solar conditions, there were no detectable high-energy electrons in this region at all. These results are important to incorporate into models of the radiation belts, to better characterize and predict the high radiation environment in near-Earth space.

Citation: Feinland, M. A., & Blum, L. W. (2025). Lightning-induced precipitation as a proxy for inner belt MeV electron decay times. Journal of Geophysical Research: Space Physics, 130, e2025JA034258. https://doi.org/10.1029/2025JA034258

—Viviane Pierrard, Editor, JGR: Space Physics

Text © 2025. The authors. CC BY-NC-ND 3.0
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The Serengeti is one of the most diverse ecosystems on Earth. The massive savanna stretches more than 30,000 square kilometers across Tanzania and southwestern Kenya, and conservation sites, including national parks and a United Nations Educational, Scientific and Cultural Organization World Heritage Site, mark its significance as one of the world’s last intact large-animal migration corridors.

Life in the Serengeti is shaped by interactions between herbivores, vegetation, fire, and rain. Every year, millions of wildebeest, zebras, and gazelles hoof it across the savanna for their great migration, an 800-kilometer loop through the Serengeti and Kenya’s adjacent Maasai Mara game reserve. The iconic migration is dictated by rainfall, with herbivores following the green grass brought by the rainy season.

New research documenting the far-reaching impact of increasing rainfall on the Serengeti will be presented on Monday, 15 December, at AGU’s Annual Meeting. Megan Donaldson, a postdoctoral researcher at Duke University’s Nicholas School of the Environment, and her colleagues will share how vegetation is consumed by both grazing herbivores and fire in the Serengeti and how that consumption is reflected in the landscape. Studies like Donaldson’s are emerging as an important area of research for scientists assessing how climate change will affect the closely intertwined biotic and abiotic components in tropical grassland ecosystems around the world.

“For now, we’re just looking at how those interactions are feeding back to each other, how increased rainfall is affecting the dynamics between vegetation, herbivores, and fire,” said Donaldson.

Rainfall, Fuel, and Food

Rainfall controls how much grass grows in the Serengeti: When rainfall is intense, grasses grow quickly.

That growth is consumed in two primary ways: by fire as fuel and by herbivores as food.

Fire can eradicate excess vegetation, which is why a previous rainy season in the Serengeti might be a reliable predictor for how much land will burn there in the near future.

More than 30 species of large herbivores consume vegetation in the Serengeti, each with its own ecological niche.

“Some are constantly on the move, others are residents, some are grazers, some browsers, others are mixed feeders, and they range in size from the minuscule dik-dik to the massive elephant. They all thrive together by seeking out seasonal sources of water and feeding differentially on the rich diversity and abundance of grasses, shrubs, and trees,” said Monica Bond, a wildlife biologist at the University of Zurich who was not part of the recent study.

Herbivores consume vegetation at a much slower rate than fire does. Under normal conditions, grazing herbivores keep grass levels low enough to reduce the spread of fire across large areas. But it can take several seasons for animal populations to adjust to differences in food availability, so as rainfall totals increase and cause explosive growth in savanna vegetation, herbivores are unable to maintain their ability to minimize the fuel available for wildfires.

In the new research, Donaldson and her colleagues examined weather station and camera trap data from sites inside Serengeti National Park in Tanzania.

In particular, the researchers tracked how recent shifts in the Indian Ocean Dipole caused rainfall totals to increase across the Serengeti. The Indian Ocean Dipole is a weather pattern similar to the El Niño–Southern Oscillation phenomenon that spawns El Niño or La Niña conditions in the Pacific. It alters wind, rain, and temperature conditions in East Africa. Between 2019 and 2024, mean rainfall totals in the Serengeti were 268 millimeters higher than in the period from 1999 through 2003.

The researchers found that within the park, rainfall was not uniform. “There’s a rainfall gradient. You get low rainfall in the south and high rainfall in the north,” said Donaldson.

In the northern Serengeti, surplus rainfall supported such rapid growth of grass that herbivore consumption had little influence on reducing the amount of fuel available for wildfires.

In the typically drier south, however, herbivores were able to keep grasses short enough to slow the buildup of fuel.

But during periods of increased rainfall, Donaldson explained, “we see that those feedbacks are quicker. You’re getting fuel buildup much quicker, and you need all the [animal] migrants to come through that system to have any effect on fire.”

Untangling a Complex Ecosystem

Between 2019 and 2024, fire size in the Serengeti increased, but the increase was more complex than “more fuel feeding more fires.”

“The number of fires necessarily isn’t changing; it seems to be staying stable,” explained Donaldson. “We’re not seeing this very strong correlation between increased rainfall and increased fire. What is driving that? Why are we seeing that? And what are herbivores doing to that? Those are the things we’re trying to tease apart right now.”

“Because the Serengeti is one of the few intact biologically functioning ecosystems left on the planet, it makes for a perfect natural laboratory.”

Future work from Donaldson and her colleagues will further researchers’ understanding of how the Serengeti’s four major players—herbivores, biomass, fire, and rainfall—connect.

“Because the Serengeti is one of the few intact biologically functioning ecosystems left on the planet, it makes for a perfect natural laboratory to study complex ecological interactions and how these are affected by climate change,” said Bond. “This research has important implications for fire management and thus for wildlife conservation in this ecologically critical landscape. It is incredible the research that they have done here in fostering understanding of how this system works.”

—Rebecca Owen (@beccapox.bsky.social), Science Writer

Citation: Owen, R. (2025), Tracing fire, rain, and herbivores in the Serengeti, Eos, 106, https://doi.org/10.1029/2025EO250444. Published on 2 December 2025. 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.

Our Sun is about halfway through its life, which means Earth is as well. After a star exhausts its hydrogen nuclear fuel, its diameter expands more than a hundredfold, engulfing any unlucky planets in close orbits. That day is at least 5 billion years off for our solar system, but scientists have spotted a possible preview of our world’s fate.

Elderly stars just get hungry.

Using data from the TESS (Transiting Exoplanet Survey Satellite) observatory, astronomers Edward Bryant of the University of Warwick and Vincent Van Eylen of University College London compared systems with stars in the main sequence of their lifetimes—fusing hydrogen, like the Sun—with post–main sequence stars closer to the end of their lifetimes, both with and without planets.

“We saw that these planets are getting rarer [as stars age],” Bryant said. In other words, planets are disappearing as their host stars grow old. The comparison between planetary systems with younger and older stars makes it clear that the discrepancy does not stem from the fact that the planets weren’t there in the first place: Elderly stars just get hungry.

“We’re fairly confident that it’s not due to a formation effect,” Bryant explained, “because we don’t see large differences in the mass and [chemical composition] of these stars versus the main sequence star populations.”

Complete engulfment isn’t the only way giant stars can obliterate planets. As they grow, giant stars also exert increasingly larger tidal forces on their satellites that make their orbits decay, strip them of their atmospheres, and can even tear them apart completely. The orbital decay aspect is potentially measurable, and this is the effect Bryant and Van Eylen considered in their model for how planets die.

“We’re looking at how common planets are around different types of stars, with number of planets per star,” Bryant said. Bryant and Van Eylen identified 456,941 post–main sequence stars in TESS data and, from those, found 130 planets and planet candidates with close-in orbits. “The fraction [of stars with planets] gets significantly lower for all stars and shorter-period planets, which is very much in line with the predictions from the theory that tidal decay becomes very strong as these stars evolved.”

Astronomers use TESS to find exoplanets by looking for the diminishment in light as they pass in front of their host stars, a miniature eclipse known as a transit. As with any exoplanet detection method, transits are best suited to large, Jupiter-sized planets in relatively small orbits lasting less than half of an Earth year, sometimes much less. So these solar systems aren’t much like ours in that respect. Studying planets orbiting post–main sequence stars poses additional challenges.

“If you have the same size planet but a larger star, you have a smaller transit,” Bryant said. “That makes it harder to find these systems because the signals are much shallower.”

However, though the stars in the sample data have a much greater surface area, they are comparable in mass to the Sun, and that’s what matters most, the researchers said. A star with the same mass as the Sun will go through the same life stages and die the same way, and that similarity is what helps reveal our solar system’s future.

“The processes that take place once the star evolves [past main sequence] can tell us about the interaction between planets and host star,” said Sabine Reffert, an astronomer at Universität Heidelberg who was not involved in the study. “We had never seen this kind of difference in planet occurrence rates between [main sequence] and giants before because we did not have enough planets to statistically see this difference before. It’s a very promising approach.”

Planets: Part of a Balanced Stellar Breakfast

Exoplanet science is one of astronomy’s biggest successes in the modern era: Since the first exoplanet discovery 30 years ago, astronomers have confirmed more than 6,000 planets and identified many more candidates for follow-up observations. At the same time, the work can be challenging when it comes to planets orbiting post–main sequence stars.

One tricky aspect of this work is related to the age of the stars, which formed billions of years before our Sun. Older stars have a lower abundance of chemical elements heavier than helium, a measure astronomers call “metallicity.” Observations have found a correlation between high metallicity and exoplanet abundance.

“A small difference in metallicity…could potentially double the occurrence rate.”

“A small difference in metallicity…could potentially double the occurrence rate,” Reffert said, stressing that the general conclusions from the article would hold but the details would need to be refined with better metallicity data.

Future observations to measure metallicity using spectra, along with star and planet mass, would improve the model. In addition, the European Space Agency’s Plato Mission, slated to launch in December 2026, will add more sensitive data to the TESS observations.

Earth’s fiery fate is a long way in the future, but researchers have made a big step toward understanding how dying stars might eat their planets. With more TESS and Plato data, we might even glimpse the minute orbital changes that indicate a planet spiraling to its doom—a grim end for that world but a wonderful discovery for our understanding of the coevolution of planets and their host stars.

—Matthew R. Francis (@BowlerHatScience.org), Science Writer

Citation: Francis, M. R. (2025), Planet-eating stars hint at Earth’s ultimate fate, Eos, 106, https://doi.org/10.1029/2025EO250448. Published on 2 December 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
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Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: GeoHealth

Heatwaves can disrupt many parts of daily life, including access to essential healthcare services. Dey et al. [2025] evaluate how heatwaves are related to where women in India give birth.

The authors analyze data from over 200,000 births during 2019-2021 and find that during periods of heatwaves, women were more likely to deliver at home instead of in a health facility. This association was stronger for warmer regions, regions without government programs supporting facility-based births, and non-Hindu populations. The study indicates that extreme heat may create barriers to healthcare services (e.g., difficulty traveling or strained health services), which makes it challenging to reach a hospital in time for delivery. This brings a major concern because giving birth at home without a skilled medical attendant may lead to higher health risks for both the mother and the newborn.

As the frequency and intensity of heatwaves increases under climate change, these findings emphasize the urgent need for early warning systems and stronger healthcare support to protect vulnerable mothers and newborns.

Citation: Dey, A. K., Dimitrova, A., Raj, A., & Benmarhnia, T. (2025). Heatwaves and home births: Understanding the impact of extreme heat on place of delivery in India. GeoHealth, 9, e2025GH001540. https://doi.org/10.1029/2025GH001540

—Lingzhi Chu, Associate Editor, GeoHealth

Text © 2025. The authors. CC BY-NC-ND 3.0
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Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: AGU Advances

Using data from the GRACE and GRACE-FO satellite missions, Rateb et al. [2025] monitored global changes in terrestrial water storage to study how hydrological extremes—floods and droughts—have developed over the past two decades. Their analysis indicates that these extremes are mainly driven by climate variability in tropical oceans, with both interannual and multi-year patterns playing a significant role.

However, the approximately 22-year satellite record is still too short to fully identify long-term drivers, which limits the ability to determine whether global extremes are increasing or decreasing. To fill data gaps in certain months, the authors use non-parametric probabilistic methods to reconstruct storage anomalies. The reconstructed data closely matched independent datasets, confirming the reliability of their approach. Overall, the study highlights the need to extend satellite observations to capture multi-decadal climate variability and better distinguish natural fluctuations from human-induced changes.

Citation: Rateb, A., Scanlon, B. R., Pokhrel, Y., & Sun, A. (2025). Dynamics and couplings of terrestrial water storage extremes from GRACE and GRACE-FO missions during 2002–2024. AGU Advances, 6, e2025AV001684. https://doi.org/10.1029/2025AV001684

—Tissa Illangasekare, Editor, AGU Advances

Text © 2025. The authors. CC BY-NC-ND 3.0
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Since the first agricultural revolution, circa 10,000 BCE, humanity has adapted its farming practices to meet climatic variation. The genesis of early farming is even thought to have resulted from a shift in seasonal conditions that favored regular planting and harvesting intervals after the last ice age.

In the modern era, the necessity to adapt has led to expansive land use, fertilization, irrigation, and other agricultural routines—powered primarily by combusted carbon and freshwater extractions—to suit local environmental conditions and meet demands of growing populations. These practices have been a boon to food supplies, but they have also contributed to many of today’s climatic and environmental challenges.

Climate-smart practices have primarily been studied in small, controlled experiments, not at the extent needed to verify their effectiveness on a large scale.

Recognition of global crises with respect to climate change and biodiversity has motivated landmark international agreements such as the Paris Agreement and the Global Biodiversity Framework. The Paris Agreement legally binds participating nations to implement land use methods that mitigate emissions and actively remove carbon from the atmosphere.

One such set of modified land management practices, known collectively as climate-smart agriculture [U.S. Department of Agriculture, 2025], is lauded as a pragmatic, low-barrier pathway to manage climate change through nature-based atmospheric carbon removal and avoided emissions (related to both land use and livestock). However, these practices have primarily been studied in small, controlled experiments, not at the extent needed to verify their effectiveness—and help motivate their adoption—on a large scale.

Recently, soil carbon experts explored the utility of applying causal approaches to quantify soil carbon accrual and avoided emissions from large-scale land management interventions and to address concerns and uncertainties that are slowing their uptake [Bradford et al., 2025a]. Such approaches have long been applied in other contexts to measure and verify treatment efficacy. In particular, methods in medical science for studying vaccine efficacy broadly offer important insights for assessing climate-smart applications.

Accounting for Carbon

Climate-smart agriculture includes a variety of management practices such as cover cropping (planting noncash crops on otherwise fallow land), reducing or eliminating soil tilling, and diversifying crops. These applications can offer various cobenefits, including increased yields; greater soil water holding capacity; improved soil microbiomes; reduced erosion and runoff; enhanced control of pests, disease, and weeds; and greater soil nutrient availability that reduces the need for chemical fertilizers [U.S. Department of Agriculture, 2025].

Such benefits are linked to the idea that the applications either avoid losses or improve gains in soil organic matter. But can we measure how much they really help?

To account for carbon lost, gained, or stored in agricultural land, soil organic matter is typically measured by elemental analysis of soil samples in a laboratory. Amounts of carbon stored are determined by tracking changes in soil carbon stocks over time. Comparing results following the application of climate-smart agriculture approaches with those following business-as-usual practices provides a measure of the approaches’ effectiveness for carbon management.

Cover crop grows amid rows of corn stubble in a farm field in Deerfield, Mass. Credit: Lance Cheung, U.S. Department of Agriculture/Flickr, PDM 1.0

Assuming this carbon accounting reveals increased soil carbon stocks, agricultural projects implementing these approaches can be considered natural climate solutions, which are valued in the voluntary carbon market for their carbon offset and removal power. For example, one project developer selling carbon credits since 2022 recently reported that their efforts have so far stored nearly 1 million tons of soil carbon in U.S. farmlands. Further, across farms in four U.S. states, the combined use of three climate-smart agriculture techniques—no tillage, cover cropping, and crop rotation of corn and soybeans—is claimed to have resulted in a shift to carbon gains from soil carbon loss using conventional practices [U.S. Department of Agriculture, 2025].

Limited Evidence, Low Adoption

Despite claims about the successes of climate-smart agricultural practices, adoption remains low. Although no-till and reduced-till methods have been implemented on more than half of all U.S. soybean, corn, and sorghum fields, cover cropping is used across less than 5% of the country’s agricultural lands.

If robust data showing that climate-smart practices lead to widespread yield increases, cost reductions, and climate benefits were available, they might be more widely adopted by growers.

A multitude of social, cultural, and economic factors—along with questions about the viability for meaningful climate change mitigation—contribute to the limited adoption of some climate-smart practices [Prokopy et al., 2019; Eagle et al., 2022]. However, if robust data showing that they lead to widespread yield increases, cost reductions, and climate benefits were available, they might be more widely adopted by growers.

Presently, most evidence supporting the benefits of climate-smart agriculture for carbon management relies on a limited set of small-plot experimental trials and projected outcomes derived from applying process-based biogeochemical models. Public and private investment in studies aimed at quantifying the practices’ efficacy through measurement, monitoring, reporting, and verification (MMRV) at scales of real-world commercial agriculture has been inhibited by the assumption that soils vary too much to measure treatment effects feasibly [Poeplau et al., 2022].

This assumption is driven by the fact that regional and national soil carbon inventories reveal substantial variation in soil carbon contents at scales within individual fields (meters to tens of meters) and between fields (kilometers to tens of kilometers)—variation that is thought to preclude detections of how agricultural practices affect carbon stocks [Bradford et al., 2023]. Yet this variability can be overcome by scaling up field-level data to multifield scales focused on understanding the average effect of interventions.

What could this scaling look like, and what cues from other fields can we use to make progress?

Adapting Methods from Medical Research

Causal approaches are used regularly in health sciences, including in vaccine trials. In later-stage trials, vaccine efficacy is quantified under conditions approximating real-world delivery by measuring the differences in the health responses of people who receive the vaccine and those who do not.

Public health scientists use large-scale clinical intervention-style experiments to account for factors that can modify real-world vaccine efficacy. Earth scientists can take direction from such trials.

Importantly, such real-world trials occur only after there is enough experimental evidence—typically from controlled laboratory experiments and small-scale clinical trials—of underlying mechanisms indicating the likelihood of broad, meaningful positive effects and minimal negative effects of the vaccine. Public health scientists use these large-scale clinical intervention-style experiments (or observational studies) to account for factors such as varied exposure risks and preexisting conditions that can modify real-world vaccine efficacy compared with efficacy under controlled conditions.

Earth scientists can take direction from such trials. Adapting this experiment structure for soil science research would allow project developers, scientists, land managers, and policymakers to assess the ability of climate-smart agricultural practices to store carbon and reduce emissions across real fields and farms. It would also better inform meaningful climate action policy initiatives.

A base of highly controlled small-scale experiments—typically conducted in plots operated by researchers—already exists that suggests the carbon benefits of improved agricultural practices under highly controlled conditions. What is missing are the large-scale intervention studies sampling soil carbon in fields that receive a climate-smart treatment (e.g., no till or reduced till, crop rotation, cover cropping) versus those that are conventionally managed [Bradford et al., 2025b].

Such studies must be undertaken with appropriate design principles to confirm whether treatment interventions cause measured carbon gains and to focus on the external validity of the experiments. In the case of climate-smart agriculture, “external validity” refers to the extent to which a study’s results are applicable to other fields receiving similar management interventions. Achieving external validity necessitates sustained observation of realistic intervention behaviors on working commercial farms and on well-defined and preserved control fields, repetition of experiments at a variety of sites, and quantification of average outcomes from interventions across fields rather than for individual fields.

Empirical causal studies at the regional scales of commercial agricultural practices should be the gold standard of evidence for evaluating the effectiveness of climate-smart approaches.

New research suggests that empirical measure-and-remeasure projects are scientifically feasible at regional agricultural scales using current best practices for soil sampling and carbon analysis [Potash et al., 2025; Bradford et al., 2023]. Potash et al. [2025], for example, simulated a randomized-controlled trial for intervention projects across hundreds to thousands of fields, incorporating known variations in soil carbon stocks and measurement errors. The results showed that such projects can reliably estimate the effects of the treatments applied.

Using causal empirical approaches can complement, rather than compete with, the development of other approaches for MMRV of carbon storage and emissions. Approaches using satellite and airborne remote sensing may, for example, enable more efficient scaling of climate mitigation projects, albeit only if they are first validated against causal empirical data.

Empirical causal studies at the regional scales of commercial agricultural practices should thus be the gold standard of evidence for evaluating the effectiveness of climate-smart approaches. Data from these experiments will provide a rigorous basis for independent validation of established and emerging digital- and model-based approaches for soil carbon MMRV. They will also build confidence that adopting climate-smart practices really does result in mitigation of carbon emissions and climate change under real-world conditions.

Acknowledgments

The perspectives presented here were informed by discussions at and outcomes from a workshop convened in October 2024 by researchers at Yale University and the Environmental Defense Fund. Funding support was provided by the Yale Center for Natural Carbon Capture and gifts to the Environmental Defense Fund from King Philanthropies and Arcadia, a charitable fund of Lisbet Rausing and Peter Baldwin.

References

Bradford, M. A., et al. (2023), Testing the feasibility of quantifying change in agricultural soil carbon stocks through empirical sampling, Geoderma, 440, 116719, https://doi.org/10.1016/j.geoderma.2023.116719.

Bradford, M. A., et al. (2025a), Agricultural soil carbon: A call for improved evidence of climate mitigation, Yale Applied Science Synthesis Program and Environmental Defense Fund white paper, Yale Appl. Sci. Synth. Program, New Haven, Conn., https://doi.org/10.31219/osf.io/uk3n2_v1.

Bradford, M. A., et al. (2025b), Upstream data need to prove soil carbon as a climate solution, Nat. Clim. Change, 15, 1,013–1,016, https://doi.org/10.1038/s41558-025-02429-4.

Eagle, A. J., N. Z. Uludere Aragon, and D. R. Gordon (2022), The realizable magnitude of carbon sequestration in global cropland soils: Socioeconomic factors, Environ. Defense Fund, New York, www.edf.org/sites/default/files/2022-12/realizable-magnitude-carbon-sequestration-cropland-soils-socioeconomic-factors.pdf.

Poeplau, C., R. Prietz, and A. Don (2022), Plot-scale variability of organic carbon in temperate agricultural soils—Implications for soil monitoring, J. Plant Nutr. Soil Sci., 185, 403–416, https://doi.org/10.1002/jpln.202100393.

Potash, E., et al. (2025), Measure-and-remeasure as an economically feasible approach to crediting soil organic carbon at scale, Environ. Res. Lett., 20(2), 024025, https://doi.org/10.1088/1748-9326/ada16c.

Prokopy, L. S., et al. (2019), Adoption of agricultural conservation practices in the United States: Evidence from 35 years of quantitative literature, J. Soil Water Conserv., 74(5), 520–534, https://doi.org/10.2489/jswc.74.5.520.

U.S. Department of Agriculture (2025), Documentation of literature, data, and modeling analysis to support the treatment of CSA practices that reduce agricultural soil carbon dioxide emissions and increase carbon storage, Off. of the Chief Econ., Off. of Energy and Environ. Policy, Washington, D.C., www.usda.gov/sites/default/files/documents/USDA_Durability_WhitePaper_01_14.pdf.

Author Information

Savannah Gupton (savannah.gupton@yale.edu), Applied Science Synthesis Program, The Forest School at the Yale School of the Environment, Yale Center for Natural Carbon Capture, Yale University, New Haven, Conn.; Mark Bradford, Alex Polussa, and Sara E. Kuebbing, The Forest School at the Yale School of the Environment, Yale Center for Natural Carbon Capture, Yale University, New Haven, Conn.; and Emily E. Oldfield, Environmental Defense Fund, New Haven, Conn.; also at Yale School of the Environment, Yale University, New Haven, Conn.

Citation: Gupton, S., M. Bradford, A. Polussa, S. E. Kuebbing, and E. E. Oldfield (2025), How can we tell if climate-smart agriculture stores carbon?, Eos, 106, https://doi.org/10.1029/2025EO250446. Published on 1 December 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.

Early in the time-twisting, exoplanet-exploring film Interstellar, a scientist on a blight-plagued Earth stares at corn in a greenhouse, watching the crop die. That scene, said Northern Arizona University doctoral candidate Laura Lee, got her thinking about growing food in difficult soils.

The idea propelled Lee, a planetary scientist and astronomer, into a new project, studying how the outer veneer of planetary bodies might be enriched to sustain crops needed for future human settlements. At AGU’s Annual Meeting 2025 on 16 December, Lee will present findings about how various amendments, such as fungi, urea-based fertilizer, and even poop, could help plants like corn grow on the Moon and Mars.

Necessary Ingredients

Plants need 17 specific elements to survive. Carbon, hydrogen, and oxygen combine to form cellulose—the building blocks of cell walls. Nitrogen helps lush green leaves flourish. Phosphorous stimulates stability-providing roots. Iron, potassium, and other nutrients are also critical for plants to function.

“If you can avoid bringing all that up, it’s super advantageous. Mass is really expensive.”

But on the Moon and Mars, the regolith—the loose outer layer of any planetary body—lacks some of these plant essentials. For instance, lunar regolith contains almost no carbon or nitrogen, said Steve Elardo, a planetary geochemist at the University of Florida who was not involved in Lee’s study.

Plus, the phosphorus that is present, at least on the Moon, isn’t in a useful form for plants, said Jess Atkin, a doctoral candidate and space biologist at Texas A&M who studies how microbes can remediate regolith to grow plants on the Moon.

Taking terrestrial soil to space is not ideal because of cost. “If you can avoid bringing all that up, it’s super advantageous,” Elardo said. “Mass is really expensive.” Taking microbes to the Moon, on the other hand, is a much lighter option.

What’s in a Regolith?

Scientists rely on data from rovers, landers, and satellite remote sensing to understand the chemistry of Martian regolith. The Apollo missions brought back 382 precious kilograms (842 pounds) of the Moon. The Chang’e and Luna missions combined brought back another ~4 kilograms of lunar samples. Because of the limited supply of real lunar regolith, most planetary crop studies, including Lee’s, rely on something called simulant, a synthetic imitation of extraterrestrial regolith.

For her experiments, Lee selected two simulants from Space Resource Technologies: one of the lunar highlands and one that approximates Martian regolith on the basis of data from both remote sensing and the Curiosity rover. But because of the lack of necessary nitrogen in both simulants, Lee tested two nitrogen-bearing media to introduce this key ingredient.

For the first, she used a synthetic urea-based fertilizer used by many home gardeners. For the second, Lee used Milorganite—a nitrogen-rich biosolid made from processing human waste produced by the population of Milwaukee, Wis. For Lee, the Milorganite imitates a nutrient-rich resource that future astronauts heading to planetary bodies will certainly have and that shouldn’t add weight to the mission payload: their own waste.

The hardened final remains from a sewage plant are called sludge or biosolids. The semisolid leftovers form desiccation cracks as they dry. This image is from a sewage plant in Kos, Greece. Credit: Hannes Globe/Wikimedia Commons, CC BY-SA 2.5

“When they’re adding human waste, the best thing they’re doing is adding organic matter” that can also help bind regolith particles together, said Atkin, who was not involved with Lee’s study.

“You can go full Mark Watney on this,” said Elardo, referencing the 2015 film The Martian, in which a botanist astronaut amends Martian regolith with the crew’s biosolids to grow potatoes. “If you compost [astronaut waste] and make it safe…it should provide a pretty good fertilizer.”

Fabulous Fungi

Lee also tested how crops grew with and without arbuscular mycorrhizae, a microscopic, symbiotic interconnection between certain fungi and the plant roots in which they reside.

“It extends that root zone, giving stability,” Atkin said, “like a glue in our soil.” The plant provides carbon to the fungi, and the fungi transfer water and nutrients, particularly phosphorus, to the plant, she explained.

In the fertilizer-only experiments, Lee found that plants grown in lunar simulant with Milorganite tended to grow larger, but in comparison, plants grown in lunar simulant with urea-based fertilizer were more likely to survive the 15-week growing period. For the Martian simulant, no plants survived in Milorganite.

There is a huge ethical question about bringing microorganisms to extraterrestrial places.

The fertilizer-only experiments provided a control to help Lee assess what happens with the addition of fungi. In the lunar experiments with fungi, no matter which nitrogen fertilizer source was used, plants grew larger than in the fertilizer-only trials. Lee also found higher chlorophyll levels in the leaves of plants grown with fungi and Milorganite. These results are signs that fungi facilitate healthier plants. Plants grown in Martian simulant amended with either fertilizer option also fared better with the addition of fungi. Although only a single plant out of six survived in Martian simulant amended with Milorganite and arbuscular mycorrhizae, this plant “produced the highest chlorophyll levels across all lunar and Martian corn, and produced the most biomass out of all plants grown in Martian regolith,” Lee wrote in an email.

“There is a huge ethical question about bringing microorganisms” to extraterrestrial places, said Lee, whether in the form of fertilizer or fungi. But any future astronauts will introduce microorganisms to the Moon and Mars via their own microbiomes, she said. Plus, 96 bags of human waste already languish on the lunar surface, divvied up between the six Apollo landing sites.

Simulant Versus Regolith

In an experiment published in 2022, a team of scientists including Elardo demonstrated that lunar regolith collected during Apollo 11, 12, and 17 could grow a plant called Arabidopsis thaliana, or thale cress. But the plants were stressed. “They grew, but they were not particularly happy,” Elardo said. The same plants produced healthy roots and shoots when grown in lunar simulants.

These findings demonstrated that for biology purposes, “[simulants] don’t capture the chemistry of extraterrestrial regoliths,” Elardo said, in part because that’s not always what simulants are designed to do. Several are made by the truckload for large-scale engineering projects, like testing the wheels of a rover destined for Mars, he explained. Moreover, the Moon’s iron isn’t in the same state as Earth’s, and it’s a version plants don’t want. Plus, real lunar regolith grains are extremely sharp and shard-like, impeding the progress of delicate roots.

Nevertheless, comparative studies such as Lee’s might be useful, Elardo said. “Can you add a fungus…that increases nutrient uptake?” he pondered. “That’s an awesome idea.”

—Alka Tripathy-Lang (@dralkatrip.bsky.social), Science Writer

Citation: Tripathy-Lang, A. (2025), Fungi, fertilizer, and feces could help astronauts grow plants on the Moon, Eos, 106, https://doi.org/10.1029/2025EO250445. Published on 1 December 2025. 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.

body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news regarding law and policy changes that impact science and scientists today.

The U.S. Environmental Protection Agency moved this week to reduce limits on fine particulate air pollution, including soot, set by the Biden administration last year. 

The administration gave up defense of a rule which lowered the standard for air pollution particles measuring less than 2.5 micrometers in diameter, also known as PM2.5. The rule, which would have been fully implemented in 2032, took the standard from 12 micrograms of PM2.5 per cubic meter of air to 9. Such tiny particles, which come from vehicle exhaust, factories, and power plants, are especially harmful to human health because they can infiltrate the lungs and the bloodstream. 

In 2024, EPA estimated the 9-microgram standard could prevent up to 4,500 premature deaths, 2,000 hospital visits, and 800,000 cases of asthma per year. 

“An abundance of scientific evidence shows that going back to the previous standard would fail to provide the level of protection for public health required under the Clean Air Act.”

On 24 November, EPA asked the U.S. Court of Appeals for the D.C. Circuit to strike down the new standard, abandoning its defense against industry trade associations and attorneys general from conservative states that had sued Biden’s EPA over the rule.

In the court filing, EPA took the side of its challengers, stating the rule was created “without the rigorous, stepwise process that Congress required.”

“EPA now confesses error,” the filing said. Though the 9-microgram standard remains in effect currently, the EPA proposed in its filing that the standard revert to the 12-microgram rule finalized in 2020.

Environmental groups said the action undermines the agency’s obligations under the Clean Air Act. “EPA’s motion is a blatant attempt to avoid legal requirements for a rollback, in this case for one of the most impactful actions the agency has taken in recent years to protect public health,” Hayden Hashimoto, an attorney for the Clean Air Task Force, a nonprofit, told AP. “An abundance of scientific evidence shows that going back to the previous standard would fail to provide the level of protection for public health required under the Clean Air Act.”

Particulate air pollution disproportionately affects Black communities and other communities of color, as well as low-income groups. One 2018 study found that people living in poverty were exposed to 35% more PM2.5 than the overall population, and Black people were exposed to 54% higher amounts.

 
Related

•  EPA to Abandon Air Pollution Rule That Would Prevent Thousands of U.S. Deaths
•  Trump EPA Moves to Abandon Rule That Sets Tough Standards for Deadly Soot Pollution
•  EPA: Health and Environmental Effects of Particulate Matter (PM)
• Some Communities Feel the Effects of Air Pollution More Than Others
•  Get Involved: AGU Science Policy Action Center

In April, a coalition of public health and community groups wrote a letter to EPA Administrator Lee Zeldin asking him to quickly implement the strengthened standard. “There is no legally viable basis for weakening it,” they wrote.

“Our communities already carry the burden of polluted air and higher rates of asthma and heart disease. Weakening soot protections will only deepen these disparities and cost more Black lives,” Yvonka Hall, executive director of the Northeast Ohio Black Health Coalition, one of the groups that signed the letter, said in a statement.

The move to vacate defense of the rule is part of a broader rollback of regulations on industrial facilities by the EPA. Earlier this year, the agency proposed repealing requirements for polluting facilities to report their greenhouse gas emissions. The EPA is expected to propose its own PM2.5 rule early next year.

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

These updates are made possible through information from the scientific community. Do you have a story about how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. Text © 2025. AGU. CC BY-NC-ND 3.0
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In Antarctica, beneath the ice, there is liquid water—and potentially a lot of it. That’s the takeaway from new research that used seismographic instruments to probe the still largely unstudied boundary between Antarctica’s bedrock and its ice sheet.

Previous hydrological studies and modeling work have found evidence of lakes and rivers beneath the Antarctic Ice Sheet, though much remains unknown about the region.

Now, using an array of seismic sensors, researchers from Stony Brook University have added more data points to the map of subglacial Antarctica, finding evidence of a layer of water-saturated sediments or rock under the ice. That layer could have implications for models of Antarctic groundwater systems, as well as for future movements of the ice sheet as it slides toward the ocean.

Looking Beneath the Ice with Earthquakes

The data, which will be presented at AGU’s 2025 Annual Meeting, come from an array of more than 600 seismic sensors strung in two long lines totaling about 600 kilometers near the South Pole, put there over the course of two field seasons in Antarctica. The sensors listen for seismic waves that travel through the upper layers of Earth and into the ice sheet.

Those waves carry the signatures of every medium through which they’ve traveled, said Weisen Shen, a geoscientist at Stony Brook University and a paper coauthor. To isolate that information, the researchers applied a mathematical technique called a receiver function to remove the waves’ source information, leaving only the signatures of what they moved through on their journey to the sensor.

In their data from beneath the South Pole, in a region known as the Pensacola-Pole Basin, the researchers found a very low velocity layer, where seismic waves travel too slowly for the conducting medium to be bedrock or ice.

While the authors can’t say exactly what this layer looks like, Shen said the best explanation is a layer of water-saturated sediments or sandstone, likely hundreds of meters thick.

“Anything we can do to try and enhance our knowledge of what’s going on…is just going to help us try and narrow down this really bizarre landscape underneath the ice.”

“We believe…there must be some aquifer system, a groundwater system, that must be preserved beneath the ice,” he said.

The water there could even be connected to groundwater elsewhere in Antarctica, Shen noted. If so, water might be moving around beneath the surface of Antarctica through hydrologically linked basins, and perhaps even out to the ocean.

That scenario could have implications for sea level rise, but, as University of Waterloo glaciologist Christine Dow pointed out, we know far too little to say for sure. In her own modeling, Dow, who wasn’t affiliated with the research, said it appears these basins aren’t connected to the ocean.

“But these are models based on our current knowledge of where’s frozen and where’s not under the Antarctic,” she said. “Perhaps this new information will change that.”

Dow welcomed new data on the mostly uncharted landscape of subglacial Antarctica, where scientists have evidence of lakes, rivers, and groundwater interacting in complex ways, but little hard evidence of the continent’s topography.

“Anything we can do to try and enhance our knowledge of what’s going on…is just going to help us try and narrow down this really bizarre landscape underneath the ice,” she said.

More Questions Than Answers

One question the new data raise is where the heat energy needed to melt the water comes from, noted Hanxiao Wu, a Ph.D. candidate at Stony Brook University and the paper’s first author. It could come from geothermal heat from below, friction caused by the movement of ice at the surface, or some combination of both.

One takeaway from the research is that estimates of geothermal heat flux below Antarctica may need to be bumped upward, Dow said. Models of ice sheet movement and evolution may also need to change to accommodate hundreds of meters of water-saturated sediments. “That’s a game changer,” Dow said.

Should there turn out to be more water beneath Antarctica than previously thought, and should that water move greater distances and in greater amounts, sea levels could rise beyond current predictions, Shen said. It’s too early, however, to estimate any of these probabilities with much certainty, he cautioned.

Right now, Shen and his fellow researchers are focused on improving their dataset and seeking collaborations with other geophysicists to map out the implications of their findings. Wu traveled back to Antarctica for the 2025–2026 field season, where the team is adding another line of seismic sensors to increase coverage and working on tracking the array to better understand changes in snow surface elevation.

In the future, they hope to add additional data from satellites, magnetotelluric surveys, and fiber-optic cables for a more comprehensive look at the ice pack and its underbelly, perhaps as part of the 5th International Polar Year in 2032.

What the scientists will find is unknown. But with millions of square miles of land underneath the ice, the potential for discovery is appropriately vast.

—Nathaniel Scharping (@nathanielscharp), Science Writer

Citation: Scharping, N. (2025), The land beneath Antarctica’s ice might be full of water, Eos, 105, https://doi.org/10.1029/2025EO250435. Published on 26 November 2025. 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.

Powerful summertime thunderstorms are injecting particulate matter from wildfires and additional moisture into the stratosphere—a layer of the atmosphere scientists have long thought was mostly pristine.

“The lower stratosphere almost looked more like a smoke cloud.”

A new study, published in Nature Geoscience, detailed these findings, which could have implications for Earth’s ozone layer and atmospheric circulation, especially as the climate continues to warm.

“We as atmospheric scientists have this preconceived notion that [the stratosphere] is a really stable, clean area of our atmosphere. We don’t think about it being perturbed all that often,” said Dan Cziczo, an atmospheric scientist at Purdue University and a coauthor of the new study. 

But in the new observations, “the lower stratosphere almost looked more like a smoke cloud,” he said.

Stratospheric Science

North America’s monsoon season starts when warm, moisture-laden air from the Gulf of Mexico collides with the Rocky Mountains. This process can create powerful summer storms familiar to those living in the U.S. Midwest.

If those storms get powerful enough, some clouds “overshoot,” or extend multiple kilometers above the troposphere and into the stratosphere—a cold, thin layer of Earth’s atmosphere beginning at about 12,000 meters (39,000 feet) above sea level.

This overshoot happens often in the United States: There are about 50,000–100,000 overshooting storms each summer, though some last only a minute or two, said Ken Bowman, an atmospheric scientist at Texas A&M University and a coauthor of the new study. 

Bowman is the lead scientist of a 6-year project called Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) that is investigating these overshooting storms. 

To study overshooting storms, DCOTSS researchers use a unique aircraft called Earth Resources 2, or ER-2, which was built by NASA and flies as high as 22,860 meters (75,000 feet)—higher than 95% of the Earth’s atmosphere. Cziczo and his team used DCOTSS data from 31 May to 27 June 2022, an active fire season in the United States, for their new study. The data came from flights over the U.S. Midwest and Great Plains that specifically targeted overshooting storms. 

Their observations showed an unexpected amount of biomass-burning particles in the lower stratosphere during periods affected by overshooting clouds.

“Once we got the aircraft into the stratosphere, we just found it to be littered with these biomass-burning particles, particles from wildfires,” Cziczo said. There had been previous evidence from flights in 2002 that biomass-burning particles existed in the stratosphere, but not to this extent—Cziczo and his team found particles as high as 4 kilometers into the stratosphere, about 4 times higher than previous detection.

The new study “is really the first time people have seen a really large contribution from smoke in the lower stratosphere,” said Brian Toon, an atmospheric scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder who was not involved in the new study. 

“When you add lots of water vapor, it changes a lot of things.”

Cziczo explained that powerful storm clouds pick up smoke, either directly from burning areas or from smoke already mixed into the troposphere, then “spit” that smoke out into the stratosphere after clouds build up and cross the boundary between the two layers. Virtually all the observed biomass-burning particles were probably transported by overshooting storms, as there are no other likely mechanisms for the particles to enter the stratosphere, Bowman said.

The particles the team observed in the lower 4 kilometers of the stratosphere will likely stay suspended there for months.

The researchers didn’t have a way to track exactly where the particles they observed originated. But wildfires across the United States and Canada in the summer of 2022 were a likely source: “We just have to sort of infer that it was the smoke that was in the Midwest,” Cziczo said.

In addition to the biomass-burning particles, the overshooting storms brought a lot of moisture to the stratosphere. As the ER-2 aircraft flew through overshooting clouds, instruments on board detected additional water, sometimes taking the stratosphere’s usual 4 or 5 parts per million of water up to 20 or 30 parts per million. 

Such an influx of water can affect the chemistry, heating, and cooling of the stratosphere, but more research is needed to figure out exactly how. “When you add lots of water vapor, it changes a lot of things,” Bowman said.

Atmospheric Alterations

The combined forces of stronger storms and more wildfires could make the occurrence of these sooty particles in the stratosphere more likely as the climate continues to warm. 

Additional biomass-burning particles in the stratosphere could have consequences for Earth’s ozone layer. Particles provide additional surface area for the stratosphere’s gas molecules to stick to, encounter other gas particles, and react. Many of these reactions over time can damage the ozone layer, a shield of ozone molecules that protects Earth from too much ultraviolet radiation from the Sun.

“It’s important to make sure we understand this so that we can see what might happen in the future.”

“This is not a paper to panic about,” Bowman said. “But as the number of wildfires increases, which it’s likely to continue doing, we’ll get more biomass-burning particles in the stratosphere. And as the climate warms up, it’s likely that the amount of overshooting convection is going to increase, so that’s going to put more material into the stratosphere.”

The findings also raise numerous questions about how additional particles in the stratosphere might affect Earth’s other atmospheric processes. Additional dark, sooty particles could heat the atmosphere, which could change its dynamics or even blur the typically stark boundary between the troposphere and the stratosphere.

“It’s important to make sure we understand this so that we can see what might happen in the future,” Bowman said.

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

Citation: van Deelen, G. (2025), Some summer storms spit sooty particles into the stratosphere, Eos, 106, https://doi.org/10.1029/2025EO250443. Published on 26 November 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.

The solar system’s oddball planet has some pretty odd moons, too. The first infrared spectra of Uranus’s small inner moons, which will be presented on 18 December at the 2025 AGU Annual Meeting in New Orleans, have shown that their surfaces are much redder, much darker, and more water-poor than the larger moons orbiting far from the planet.

“We were trying to see how these properties varied across the rings and moons,” said Matt Hedman, a planetary scientist at the University of Idaho in Moscow and a coauthor on the research. “We didn’t have a lot of information about their spectra before because they’re hard to observe.”

The new observations also revealed that some moons were not quite where they should have been, highlighting how much more astronomers have to learn about the dynamics of the Uranian system.

Small, Dark, and Red

In 1986, Voyager 2 flew past Uranus in humanity’s only visit to the system. At that time, astronomers knew only of the planet’s five major moons and a handful of rings. Voyager 2 discovered 11 more moons and was able to roughly measure their sizes. Since then, scientists have used ground- and space-based telescopes to discover more than a dozen additional satellites, bringing Uranus’s moon total to 29.

Many of the more recently discovered moons are pretty tiny, from Sycorax at 150 kilometers across to Mab and Cupid at just 10 kilometers. Most of them also orbit within or just outside Uranus’s ring system, close to the much brighter planet.

All of these properties have made it tricky for astronomers to learn more about the smallest Uranian moons. That’s where the infrared powerhouse James Webb Space Telescope (JWST) comes in.

This diagram shows the orbital distances of Uranus’s inner moons and rings, to scale. Uranus is placed at the top of the diagram. Click image for larger version. Credit: Ruslik0/Wikimedia Commons, Public Domain

“Part of what makes JWST particularly good for this compared to, say, Hubble and other optical telescopes, is that in the infrared, Uranus is much fainter, so you can see the things orbiting it way more easily,” Hedman explained. What’s more, all of the spectral features the team was interested in, like water ice, occur at wavelengths that JWST can observe.

The researchers observed Uranus at several infrared wavelengths in February and got a deep look at the inner portions of the planetary system. They wanted to characterize the known small moons and search for new ones. They did discover a previously unknown moon, temporarily named S/2025 U1, orbiting just outside the epsilon ring.

Those observations also provided the first information on the infrared brightnesses of the smallest moons, many of which have remained elusive since the Voyager flyby.

“Most of the rings and inner moons show very similar properties,” Hedman said. They tend to be much redder, darker, and more water-poor when compared with the larger outer moons Miranda, Ariel, Umbriel, Titania, and Oberon.

“And then there’s Mab,” Hedman added.

The new spectra show that Mab’s surface is bluer and more water-rich than the other inner moons, said Jacob Herman, a physics graduate student at the University of Idaho and lead author on the research. In fact, its surface spectrum looks very similar to Miranda’s, the major moon that orbits closest to the rings and to Mab. Miranda’s jigsaw surface suggests a messy history.

“There is still much to be discovered about Uranus’s small inner moons, particularly regarding their origin, composition, and long-term orbital stability.”

Did the two moons encounter each other sometime during Uranus’s chaotic past? Could that encounter be related to Uranus’s mu ring, which is likely generated by material sloughing off Mab? Hedman hopes that future observations or a long-term mission to Uranus will provide those answers.

“These new measurements significantly expand our current knowledge, revealing, for instance, striking variations in the composition and reflectivity of the surfaces of moons such as Mab, Cupid, and Perdita,” said Jadilene Xavier, an astrophysicist at São Paulo State University in Guaratinguetá, Brazil, who was not involved with this research.

“There is still much to be discovered about Uranus’s small inner moons, particularly regarding their origin, composition, and long-term orbital stability,” Xavier said. “More precise data on their density, three-dimensional shape, and surface properties would be essential to determine whether these moons are fragments produced by collisions, captured objects, or primordial remnants associated with the formation of Uranus’s ring system.”

Just a Little Bit Off

Because Voyager 2 spent only a short time visiting Uranus, it could provide only limited information about the small moons’ orbital periods and distances, sometimes with large uncertainties. When the researchers compared the moons’ current positions with the positions predicted by Voyager 2 data, some of the moons were not where they seemingly should have been.

“Perdita was quite a bit off,” Herman said. “And there’s also Cupid, which was surprising.” The positions of Cordelia, Ophelia, Cressida, and Desdemona were also off, but not by much. The team is still trying to figure out whether the differences are just a matter of having more precise observations of these tiny objects or if there are unknown dynamics in play.

“These new observations are quite useful for improving our understanding of the inner Uranian system, especially its orbital dynamics.”

“These new observations are quite useful for improving our understanding of the inner Uranian system, especially its orbital dynamics,” said Matija Ćuk, who researches solar system dynamics at the SETI Institute in Mountain View, Calif.

Ćuk, who was not involved with this research, pointed out that Cordelia and Ophelia shepherd Uranus’s epsilon ring, Cressida and Desdemona are part of a pack of moons with chaotic orbits, and Perdita is known to interact with another moon, Belinda. “So the fact that these [five] moons are not in their predicted positions is valuable for understanding the system, but I wouldn’t say it’s unexpected,” Ćuk said.

These observations hint at just how many mysteries Uranus is still hiding.

“For a dynamicist like me,” Ćuk said, “knowing the precise masses of these moons would be ideal, because then we could predict their future interactions and also estimate with some confidence how stable they are on long timescales.”

Hedman and their team plan to observe the Uranian system again with JWST, are looking through archived and technical images, and hope to establish long-term monitoring to better understand the moons’ dynamics and possibly estimate their masses. The researchers are also leaning on their colleagues who simulate planetary orbits to better understand how Uranus’s moons and rings might be influencing each other.

“It’s a very dynamic and interconnected system,” Herman said.

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

Citation: Cartier, K. M. S. (2025), Uranus’s small moons are dark, red, and water-poor, Eos, 106, https://doi.org/10.1029/2025EO250442. Published on 25 November 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.

The rapid retreat of glaciers, an increasingly common phenomenon, could potentially lead to complex changes in ocean chemistry. A new study has revealed that sediment runoff from retreating glaciers is less nutritious for marine life than meltwater from stable glaciers. This finding has important implications for high-latitude marine ecosystems, such as the Gulf of Alaska, where trace metals like iron and manganese are essential for supporting microorganisms at the base of the food web.

Glacial runoff, which carries sediments produced by the relentless grinding of ice on the bedrock below, is an important source of trace metal micronutrients in the ocean. These nutrients, in turn, are essential for phytoplankton growth, which sustains the marine food web and plays a major role in absorbing atmospheric carbon dioxide.

Intrigued by the effects of climate change on nutrient availability, a team of researchers used two adjacent glaciers on Alaska’s Kenai Peninsula as a natural laboratory. One of them, Aialik Glacier, is stable and terminates on the sea, while the other, Northwestern Glacier, has retreated inland approximately 15 kilometers (9.3 miles) since 1950. Because both glaciers erode the same bedrock, the researchers knew the source material for their sediments would be nearly identical.

In late May 2022, as seasonal melting intensified, the team—led by marine chemist Kiefer Forsch, who conducted the research as a postdoctoral fellow at Scripps Institution of Oceanography and is now at the University of Southern California—collected samples from the fjords of both glaciers. Working from a small aluminum boat provided by Kenai Fjords National Park, they sampled and analyzed surface water, suspended sediments, and iceberg material, looking to analyze the concentration and bioavailability of metals like iron and manganese, as well as macronutrients such as phosphorus. (Bioavailability describes the proportion of nutrients that is readily usable by marine organisms.)

The analysis revealed important differences in the proportion of bioavailable metals in the sediment plumes. Sediments from the stable Aialik Glacier were substantially richer, with approximately 18% of the iron and 26% of the manganese in bioavailable forms. In contrast, the retreating Northwestern Glacier’s sediments contained only 13% bioavailable iron and 14%–15% bioavailable manganese. The researchers described their findings in Nature Communications.

Stale Nutrients

Researchers think this drop in bioavailable nutrients may be caused by the time lapse between when the sediments were produced and when they were released into the ocean. In the stable Aialik Glacier, which ends directly in the fjord, the sediments have a very short trip from the point of erosion to the ocean. This short distance results in fresh and labile—reactive—nutrients that microorganisms can readily use.

“The impact it could have on the ecology downstream might be muted quite a bit by its lower bioavailability.”

The retreating Northwestern Glacier’s erosive action has moved far inland. As its sediments are transported to the ocean by fluvial waters, they are chemically altered, transformed into less reactive compounds. By the time the runoff reaches the fjord, Forsch said, “it’s lost a lot of its nutritious value just by sitting there, chemically weathering.”

But that’s not the whole story. In absolute terms, the amount of bioavailable metals was similar in both fjords because the overall volume of sediment in the retreating glacier’s fjord was higher. Even if the runoff was less nutritious, researchers concluded, there seemed to be more of it.

Regardless, “the impact it could have on the ecology downstream might be muted quite a bit by its lower bioavailability,” Forsch said.

The Coast Is Not the Ocean

The implications for nutrient availability extend beyond trace metals. Glaciers that terminate in the ocean, called tidewater glaciers, provide an extra benefit by inducing powerful upwelling currents. Meltwater enters the ocean at depth and quickly rises, bringing with it deep ocean water loaded with macronutrients like nitrogen and phosphorus. Phytoplankton near the ocean surface consume these nutrients and can themselves become bioavailable to the fjord’s primary consumers like zooplankton and krill. This upwelling mechanism is what makes these fjords highly productive ecosystems.

“Losing this macronutrient supply [as tidewater glaciers retreat inland] is considered the more devastating impact for coastal ecosystems,” said Jon Hawkings, a glacial biogeochemist at the University of Pennsylvania. “There’s much more iron and manganese in these fjords than there is in the ocean by orders of magnitude; they’re limited by nitrogen mainly.”

“Once the upwelling mechanism is lost, the fjord starts to become less productive,” Forsch added.

Making things worse, when a glacier retreats onto land, its sediments are ultimately delivered at the ocean surface, creating a plume that blocks light, further inhibiting phytoplankton growth. In terms of the geochemistry and biology of these ecosystems, “it’s not really a dial, it’s a switch that occurs when a glacier retreats onto land,” he said.

While the loss of tidewater glaciers will likely lead to reduced productivity within fjords, the implications for the wider ocean are different. The Gulf of Alaska is home to very important fisheries, but its overall productivity is limited by micronutrients like iron, rather than macronutrients such as nitrogen and phosphorus. Glacial retreat might accelerate the delivery of more dissolved iron and manganese out of the fjords and onto the continental shelf, but at the same time these sediments will be less nutritious than they used to be.

In fact, Hawkings suggested, researchers might want to look “off the fjords.… This is probably where this work should go next, looking at these plumes as they exit the fjords into the Gulf of Alaska.”

The study “opens up a number of new questions,” Hawkings said, but much more research is needed to answer them. “What is the impact…for marine productivity? Is this just a one-off? Should we go back to the same place and test again? What about other places like Greenland, Alaska and Patagonia? … The jury is still out in my view.”

—Javier Barbuzano (@javibar.bsky.social), Science Writer

Citation: Barbuzano, J. (2025), Glacier runoff becomes less nutritious as glaciers retreat, Eos, 106, https://doi.org/10.1029/2025EO250431. Published on 25 November 2025. 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.

This is an authorized translation of an Eos article. Esta es una traducción al español autorizada de un artículo de Eos.

Gestionar los incendios en bosques tropicales puede ser una tarea muy abrumadora: los taladores y los pirómanos comúnmente se mueven más rápido que los equipos de primera intervención, los recursos son escasos y el territorio es inmenso. En la Amazonia Brasileña, estos obstáculos aprietan a un sector ambiental que crónicamente ha recibido pocos fondos, cuyos agentes de campo enfrentan amenazas de granjeros y, cada vez más, de el crimen organizado.

En 2024, los incendios arrasaron con 30.8 millones de hectáreas en Brasil, un 79% más que en 2023. Más del 80% del área total que se quemó se encontraba dentro de la Amazonia Legal, según la plataforma de datos ambientales MapBiomas (La Amazonia Legal es una región designada por el gobierno que comprende los 9 estados que están en la cuenca del Amazonas). Debido a la escala de los incendios, en agosto de 2024, el Instituto Brasileño del Ambiente y Recursos Naturales Renovables de Brasil (IBAMA, por sus siglas en portugués) incrementó la cantidad de vigilantes a 2 227 brigadistas (bomberos), con 1 239 de ellos – más de la mitad – con base en la Amazonia Legal.

Millones de hectáreas en Acre

Acre es el estado más al oeste de Brasil, colinda con Perú y Bolivia y es parte de la Amazonia Legal. En Acre, cuatro brigadas de incendios profesionales con 68 bomberos de tiempo completo operan en tres municipalidades y un área protegida. Una brigada voluntaria también opera en la ciudad más grande, que también es la capital, Rio Branco.

Con cerca de 14 millones de hectáreas de bosque que patrullar, estos grupos apenas pueden cubrir una fracción del territorio de Acre.

Resulta que la ciencia ha sido una herramienta importante para llenar el hueco, ya que el desafío de combatir el fuego en Acre no es solo sobre la falta de grupos en el campo; también está relacionada al acceso de datos. La información ambiental de Brasil está esparcida a lo largo de varias agencias: El Instituto Nacional de Investigación Espacial (INPE, por sus siglas en portugués), agencias ambientales federales como el IBAMA y el Instituto Chico Mendes para la Conservación de la Biodiversidad, la agencia Nacional de Agua (ANA, por sus siglas en portugués), y el centro Nacional para Monitoreo y Alertas de Desastres Naturales de Brasil, así como secretarías individuales de estado, cada una trabajando con sus propias prioridades y cadencias.

Sin datos arreglados en formatos compatibles, algunos de ellos se pueden sobrelapar o contradecir. “Para saber dónde tenemos que actuar, necesitamos información calificada, tenencia de tierras, zoneamientos y puntos calientes de incendios. Sin eso, cualquier política pública para incendios o deforestación va a ser inefectiva en el Amazonas”, dijo Claudio Cavalcante, jefe del Centro para Geoprocesamiento Ambiental (CIGMA, por sus siglas en portugués), el centro geoespacial que Acre creó dentro de la Secretaría del Ambiente en 2020 para conectar la deforestación y el monitoreo de incendios con la respuesta de políticas públicas.

CIGMA ha hecho los esfuerzos de integrar los datos de todas las agencias estatales y federales de Brasil para informar a los agentes en el campo. “Hemos trabajado con estratificación de datos: deforestación [en áreas] de 1 a 5 hectáreas y luego de 10 a 50. Automatizar algunos flujos de datos ha sido un trabajo muy complejo y laborioso” añadió Cavalcante, quien formó parte de una junta con investigadores, comunicadores y expertos en políticas públicas en las oficinas centrales del CIGMA en julio.

La mirada en los datos

Toda la integración sucede en el Cuarto de Situaciones de CIGMA, donde científicos y analistas evalúan alertas de incendio en vivo, niveles de los ríos, lluvia, índices de sequía y otra cantidad de datos.

“Todos los mapas para la acción en el campo se desarrollan aquí. También preparamos los reportes y notas técnicas mensuales de la deforestación”, dijo Quelyson Souza, quien coordina el Grupo de Mando y Control Ambiental de la Secretaría Ambiental de Acre.

Quelyson Souza, quien coordina el Grupo de Comando y Control Ambiental de Acre, explica cómo las alertas de tala funcionan y cómo esos datos pueden ser integrados en las respuestas para el combate a los incendios. Crédito: Bibiana Garrido/IPAM Amazonia

El sistema de CIGMA fusiona las alertas de incendios del INPE con los datos de tenencia de tierras y zoneamiento para identificar potenciales infractores. Los datos hidrogeológicos de ANA, la agencia de agua, se actualizan cada 15 minutos y alimentan los datos de la Defensa Civil y el Departamento de Incendios del estado. Los sensores de calidad del aire detectan humo que viene de la selva dentro y fuera de los límites de Brasil.

Para el coordinador de las Operaciones de Protección Ambiental del Cuerpo de Bomberos de Acre, el Mayor Freitas Filho, los datos científicos a los que sus cuerpos tienen acceso en el campo “son esenciales para optimizar y refinar el uso de los recursos operacionales”. El departamento de incendios de Acre lidera la Operación Controlada de Incendios, la cual se enfoca en integrar los equipos de agentes militares y ambientales para combatir los incendios en la estación seca, que abarca la segunda mitad del año.

Según un informe de manejo de incendios en la selva del Amazonas publicados este mes por el Instituto de Investigación Ambiental de la Amazonia (IPAM Amazônia), Acre tiene un modelo muy efectivo para vincular datos y gobernanza que recomienda sistemas de alerta temprana e intercambio abierto de datos para que las municipalidades puedan actuar de forma rápida.

Lecciones de Acre

A pesar de los desafíos, Acre resalta como uno de los pocos estados Amazónicos donde científicos, bomberos y creadores de políticas públicas comparten un mismo cuarto.

“Es inspirador ver la evolución del Cuarto de Situación de Acre. Lo uso como un ejemplo nacional porque la acción sucede en el campo, incluso más allá de las fronteras”, dijo Liana Anderson, una investigadora de percepción remota en el INPE.

“Es mucho más difícil que nos engañen los delincuentes que quieren salirse con la suya con sus delitos medioambientales”

Mientras Brasil se prepara para albergar la COP30 (la Conferencia de Cambio Climático de las Organización de las Naciones Unidas) en Belém, científicos y tomadores de decisiones esperan que la experiencia de Acre pueda ser un ejemplo de manejo del ambiente centrado en la ciencia: las bases de datos unificadas, los paneles compartidos y la colaboración pueden convertir a la información en planeación y acción.

“Cuando tenemos una idea más clara con la información a la que tenemos acceso ahora, es mucho más difícil que nos engañen los delincuentes que quieren salirse con la suya con sus delitos medioambientales”, dijo Souza. “Es como cuando te levantas la venda de un ojo cuando estas jugando a la gallina ciega”

—Meghie Rodrigues (@meghier.bsky.social), Science Writer

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.

This translation by Anthony Ramírez-Salazar (@Anthnyy) was made possible by a partnership with Planeteando and GeoLatinas. Esta traducción fue posible gracias a una asociación con Planeteando and GeoLatinas.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Earth’s Future

Groundwater supports billions of people, but many regions are removing it from aquifers faster than nature can refill them. Bhalla et al. [2025] examine the concept of “peak groundwater”, the moment when use reaches its maximum and begins to decline due to physical, economic, or policy limits. The authors trace how climate pressures, population growth, and management choices interact to determine when those limits arrive. They show that peak groundwater is not only a physical threshold but also a social and institutional one, shaped by how communities plan for scarcity.

The review offers a clear framework for recognizing early signs of stress and explores practical actions that can extend the life of aquifers. By bringing together insights across disciplines, it lays out pathways for governments, water managers, and communities to respond proactively. This synthesis offers a timely guide for protecting groundwater in an era of rising uncertainty.

Citation: Bhalla, S., Cherry, J. A., Konikow, L. F., Taylor, R. G., & Parker, B. L. (2025). Peak groundwater: Aquifer-scale limits to groundwater withdrawals. Earth’s Future, 13, e2025EF006221. https://doi.org/10.1029/2025EF006221

—Kelly Caylor, Editor-in-Chief, Earth’s Future

Text © 2025. The authors. CC BY-NC-ND 3.0
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Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: Community Science

Frontline communities are commonly described as groups most affected by environmental and social challenges. Marston et al. [2025] offer a broader definition based on the experiences of community-based organizations that directly serve these communities.

Drawing on surveys, interviews, and text analysis, the authors show that “frontline” refers not only to vulnerability but also to active leadership, resistance, and cultural strength. The study finds that community-based organizations want support that respects their self-determination and avoids imposing outside definitions of success. They also emphasize the need for respectful, two-way partnerships rather than top-down guidance. These insights matter because misalignment between funders and communities can weaken well-intended projects. The study provides a rare look at what frontline organizations say they truly need. Overall, it offers practical guidance for building ethical, reciprocal, and community-centered partnerships.

Citation: Marston, R., Lutz, N., Mangabat, D., Sánchez Ainsa, G., Stober, J., Brown, M., & Turner, K. M. (2025). A mixed-methods needs assessment of frontline communities: Insights for engagement and partnerships between communities and intermediary organizations. Community Science, 4, e2025CSJ000133. https://doi.org/10.1029/2025CSJ000133  

—Claire Beveridge, Editor, Community Science

Text © 2025. The authors. CC BY-NC-ND 3.0
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Imagining Earth millions of years ago—its landscapes, atmosphere, temperature—is challenging.

In Antarctica, however, rare formations known as blue ice areas may offer a distinct look into that deep past. These areas, which make up barely 1% of the continent, form where strong winds strip away surface snow. Not all blue ice areas contain very old ice, but sometimes the slow movement of the ice sheet preserves ancient layers.

The Allan Hills region, situated on the edge of the East Antarctic Ice Sheet, is one such blue ice area. Here researchers have discovered ice up to 6 million years old—the oldest yet found.

Their study of the ice, published in Proceedings of the National Academy of Sciences of the United States of America, revealed that parts of it formed during periods far warmer than today—times when sea levels were higher and open forests and grasslands covered much of the planet.

The Allan Hills ice cores are not continuous. The oldest continuous ice core, also extracted from Antarctica, may reach back about 1.2 million years. Scientists compare continuous cores to a video: an uninterrupted, sequential history. Blue ice samples like the ones taken from Allan Hills, on the other hand, function as scattered fragments or disassembled snapshots that capture events beyond the video’s timeline.

“The advantage of Allan Hills is how far back these snapshots extend,” said Sarah Shackleton of the Woods Hole Oceanographic Institution and lead author of the study. “Modeling suggests the oldest possible continuous ice core in Antarctica might not go beyond 1.5 million years. To study earlier times, we need alternative samples.”

The Allan Hills project is part of the Center for Oldest Ice Exploration (COLDEX), which seeks to uncover the oldest possible ice records to better understand Earth’s climate history.

A Frozen Archive of Deep Time

The team, led by Shackleton and John Higgins of Princeton University, drilled 200 meters to uncover these ice fragments that trap “ancient precipitation—and, more importantly, ancient air,” Higgins explained. The researchers measured isotopes of gases (such as argon-40) to estimate the ice’s age and isotopes of water (such as oxygen-18 and deuterium) to reconstruct past climates.

According to the study, the Antarctic region cooled by about 12°C over the past 6 million years, documenting the long-term transition from a relatively mild Miocene to the relatively icy world we know today.

This record is critical because while the planet has sustained much hotter temperatures, many of its human inhabitants have not: Although the last interglacial period was warmer, we have rarely experienced the planet as warm as it is today. The past is a valuable source for identifying potential warming scenarios.

“These are pieces of a larger puzzle,” said Lidia Ferri, a glaciologist with the PARANTAR project, a research project carried out at the Universidad de Oviedo in Spain to study Antarctica’s South Shetland Islands. “We can establish cycles and identify inflection points. If the ice disappears, other factors are triggered, like changes in atmospheric dynamics and ocean currents. It’s a deeply interconnected system.”

Toward Future Climate Projections

“We use the planet’s past climate as a way to ground-truth the models we’re developing to predict what’s ahead.”

A main question posed by the new research is why past climates were so warm: Was it because concentrations of atmospheric greenhouse gases were higher, or were other factors at play? By studying the atmospheric remnants trapped in blue ice, the researchers hope to refine the models used to project Earth’s future.

“We use the planet’s past climate as a way to ground-truth the models we’re developing to predict what’s ahead,” Shackleton explained.

Ferri concurred, noting the value of gathering data from different time periods. “Today’s models are becoming more precise because the data is more varied,” she said. “The temperature increase predicted for the next 50 years isn’t the same as one 10,000 years ago, and this ancient data helps enrich those models.”

Despite spartan accommodations and extreme weather, researchers plan to return to Antarctica to collect more data from the PARANTAR project. Credit: Jordi Rovira

The team plans to return to Allan Hills, though Antarctic fieldwork is notoriously challenging. “We’re in a remote field camp with no permanent structures,” Higgins said. “It’s incredibly windy and completely isolated.”

—Mariana Mastache-Maldonado (@deerenoir.bsky.social), Science Writer

Citation: Mastache-Maldonado, M. (2025), New lessons from old ice: How we understand past (and future) heating, Eos, 106, https://doi.org/10.1029/2025EO250441. Published on 24 November 2025. 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: Biogeosciences

Many ecosystems on Earth are affected by pulses of activity: temperature swings between seasons, incoming and outgoing tides, the yearly advent of rainy periods. These variations can play an important role in providing nutrients and other important inputs, but climate change often makes the amplitude of these pulses more extreme, with sometimes catastrophic results.

We need better data on the effects of changes to these pulses of activity, argues Lee. The author describes ongoing efforts to gather such data using the eddy covariance method, which measures exchanges between ecosystems and the atmosphere. The work focuses on fluxes in drylands and coastal blue carbon ecosystems—two ends of the dryness spectrum that are home to high levels of biodiversity and carbon storage and that are under increasing threats from climate change.

Scientists are gathering data from networks of flux towers, with plans to expand their data collection methods, for example, pairing mobile measuring devices with existing towers and synergizing flux data with other measurements. These strategies are increasingly important, the author notes, for assessing unconventional water inputs such as tides and condensation during dry conditions, as well as considering how disturbances like wildfire smoke and dust storms affect ecosystem function. The author argues that understanding how ecosystems are adapting to recent changes to these and other factors is crucial for refining Earth system models and constructing more accurate predictions of how ecosystems will adapt—or fail to adapt—in the future.

The author and his colleagues are also exploring the use of machine learning for Earth science endeavors and are pursuing hybrid approaches that combine process-based models with machine learning techniques. A key advantage of hybrid models is their usefulness in solving parameterization problems and the option to incorporate additional data sources, he notes. These advances could help unlock the potential of flux data to reveal crucial insights about our changing world. (Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2025JG009249, 2025)

—Nathaniel Scharping (@nathanielscharp), Science Writer

Citation: Scharping, N. (2025), Understanding flux, from the wettest ecosystems to the driest, Eos, 106, https://doi.org/10.1029/2025EO250438. Published on 24 November 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.

Over the weekend, Planet captured near-perfect images of the Mae Moh Mine landslide in Thailand.

Last week, I posted a set of Planet satellite images that captured most of the 4 November 2025 landslide at Mae Moh Mine in Thailand. However, there was considerable cloud in the imagery, which prevented a full understanding of the landslide. Over the last few days, near perfect conditions have allowed a full, cloud-free image to be captured by Planet:-

The aftermath of the 4 November 2025 landslide at Mae Moh Mine in Thailand. Image copyright Planet, captured on 22 and 23 November 2025, used with permission.

This image is a composite of two sets captured on 22 and 23 November 2025. The crown of the landslider is on the west side, with the failure moving towards the east.

I think there are twof interesting aspects to this landslide. The first is the light coloured material in the upper part of the landslide – this is the mine waste that was being deposited shortly before the failure. It is the dumping of this mine waste that is my primary hypothesis for the cause of this landslide.

The second is the configuration towards the toe of the landslide (on the east side of the image). This is the area in question:-

The lower part of the 4 November 2025 landslide at Mae Moh Mine in Thailand. Image copyright Planet, captured on 22 and 23 November 2025, used with permission.

I have placed a marker at a key point on the image. The main part of the landslide terminates in the area of the marker, but a smaller flow type failure has then developed from this point. This appears to have been quite mobile – note how a lobe has moved to the north. The main portion has moved generally eastward, with one lobe reaching the pond, and another moving towards the southwest. There are indications that this SW tending portion might have been the final movement. The distance from marker to toe is over 1,400 metres – this was a major event in its own right. I’m quite intrigued by this lower failure – was this saturated mine waste that failed through undrained loading, for example?

It is worth reiterating that the 4th November 2025 event is not the first major failure of waste at Mae Moh Mine – a 70 million cubic metre failure occurred on 18 March 2018. In fact, I wrote about that landslide too, back at the time of the failure. I included this quote, originally from The Nation:-

Maliwan Nakwirot, a resident living near the mine in Lampang, yesterday said a landslide in the area on Sunday was the result of misconduct by the mine operator, which had been piling excavated soil into unstable piles instead to storing it in abandoned mine pits.  It is not the first time that there have been landslides at Mae Moh mine. There have already been three major landslides at the mine since last year, as these mountains of soil are not stable and are ready to slide anytime,” Maliwan said.

Interesting! Finally, a brief note as to the scale of this landslide. It covers an area of about 5.7 km2 – this is extremely large. The 2018 failure covered an area of 1.56 km2 and had a volume of 70 million m3. The surface area of this failure is about 3.65 times as large. The volume is unlikely to scale in a linear manner, but might seem to indicate that the volume may exceed 100 million m3? To put that in context, the infamous 2013 Bingham Canyon landslide was “only” 55 million m3.

Reference

Planet Team 2025. Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/

Return to The Landslide Blog homepage Text © 2023. The authors. CC BY-NC-ND 3.0
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Shackleford Banks is an 8-mile-long barrier island off the coast of North Carolina made up of sandy beaches, marshes, and maritime forests. There are no vacation rentals, boardwalks, or seafood restaurants serving the residents of Shackleford Banks. That’s because the residents are more than 100 wild horses that call the sandy dunes of this island home.

The delicate ecosystem of Shackleford Banks is facing the effects of a changing climate, such as increasingly volatile storms and flooding, drought, erosion, and saltwater intrusion. The island’s low elevation means its freshwater sources can be infiltrated with salt water during king tide events and storm surges. During stretches of drought, freshwater sources for the island’s equine residents can run dry, leaving the horses to compete for these vital resources.

“These horses have been out here long enough to adapt and survive, but freshwater availability is a critical resource,” said Matthew Sirianni, a geoscientist at East Carolina University who will present his research on 16 December at AGU’s Annual Meeting. Sirianni and colleagues monitored freshwater sources on Shackleford Banks, finding that horse behavior changed when freshwater sources were scarce. As saltwater intrusion and coastal hazards increase along the islands off the coast of North Carolina known as the Outer Banks, these findings can improve understanding of how to manage wildlife during a changing climate.

Foraging for Fresh Water

Wild horses have lived on Shackleford Banks for centuries. One theory suggests they arrived in the 1500s, swimming to shore after Spanish explorers were shipwrecked along the East Coast. Genetic testing suggests today’s Shackleford Banks horses are related to Spanish horse breeds, but early English settlers also brought horses with them that may also have escaped or been abandoned along the Outer Banks.

A horse digs in a pool of surface water at a groundwater seep during low tide on Shackleford Banks. These temporary pools will be flooded by the next high tide. Credit: Matthew Sirianni

Today, Shackleford Banks’s wild horse population must be kept to a manageable number so that the island and its resources aren’t overwhelmed. National Park Service workers dart the mares with hormonal birth control each year to keep herd size low. The small, hardy equines have adapted to a life of eating marsh grass, sea oats, and wax myrtle. They drink from ponds and freshwater seeps, and they also dig holes in the sand to reach the freshwater belowground when other sources have dried up.

In the new study, researchers monitored surface and groundwater levels and conductivity—a proxy measurement for salinity because higher conductivity values mean saltier water—in six water sources (two ponds, one groundwater seep, and three dig sites) located across the island.

“Barrier islands often develop a freshwater lens in the subsurface that floats on top of the denser, saltier water,” Sirianni said. “By monitoring water level and water conductivity, we can, over time, see whether the freshwater lens is shrinking, growing, or getting saltier, which tells us how the island’s water resources are responding to things like tides, storms, or droughts.”

Researchers installed motion-activated trail cameras near the water sources to capture still shots of animals drinking. They then grouped time-stamped photos to connect the horses’ drinking activities with water level and conductivity data. From there, they searched for water usage patterns, as well as for information about how long horse-dug holes (some as deep as 3 feet) stayed full of fresh water.

“Preliminary results from July 2024 to April 2025 indicate that horses spend more time drinking at dig sites, where conductivity is lower and more stable, compared to ponds and the groundwater seep, where conductivity is higher and more variable. However, when rainfall is low, dig sites often run dry, leading horses to drink from these higher-conductivity sources,” Sirianni said.

A Saltier Future?

“In the past, we’ve said that horses wouldn’t drink brackish water, but we were wrong. They do drink brackish water when that’s the only thing available to them.”

“With the research that [Sirianni] is doing, we have learned that these ponds can be really brackish,” said Linda Kuhn, a volunteer veterinarian with the National Park Service who was not involved with the research. “In the past, we’ve said that horses wouldn’t drink brackish water, but we were wrong. They do drink brackish water when that’s the only thing available to them.”

If the freshwater sources become saltier, history has already shown how the wild horses could be in trouble. On the island of Chincoteague, Virginia, equine deaths and illness were linked to a toxic increase in salinity in freshwater supplies, possibly wrought by the storm surge from Hurricane Erin.

It took 2 weeks for volunteers and observers to figure out what was wrong at Chincoteague. “Here we have [Sirianni] giving us data in real time. He also has cameras out there so he can see who’s drinking.” In light of what happened to the Chincoteague ponies after Hurricane Erin, “it’s just such an important study at this time,” Kuhn said.

“These horses have been here for many years and weathered many storms, so…they are a symbol of wildness and freedom even in the face of adversity.”

And with the potential for stronger, damaging storms in the future, the wild horses in this precarious island habitat may face more water and food shortages—along with danger from the land itself. Previous modeling studies suggest sea level rise will cause the already shallow groundwater table to reach the surface, as well as cause the shoreline to retreat as land subsidence and erosion worsen.

Sirianni plans to continue monitoring Shackleford Banks’s wild horses and water sources through at least July 2026 while he works on a final study manuscript about his findings. But he hopes to fund this research into the future. “These horses have been here for many years and weathered many storms, so I like that they are a symbol of wildness and freedom even in the face of adversity,” he said.

—Rebecca Owen (@beccapox.bsky.social), Science Writer

Citation: Owen, R. (2025), What salty water means for wild horses, Eos, 105, https://doi.org/10.1029/2025EO250433. Published on 21 November 2025. Text © 2025. The authors. CC BY-NC-ND 3.0
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Source: Geophysical Research Letters

Ancient Mars boasted abundant water, but the cold and dry conditions of today make liquid water on the Red Planet seem far less probable. However, the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) detected strong radar reflections from a 20-kilometer-wide area over the base of Mars’s southern polar ice cap, hinting at the possibility of liquid water below the icy surface. Such a finding would have major implications for the planet’s possible habitability.

But sustaining liquid water underneath the ice might not be feasible without very salty brines or localized volcanic heat. Scientists have deliberated about other possible “dry” explanations for the bright reflections detected by MARSIS, such as layers of carbon dioxide and water ices or salty ice and clay causing elevated radar reflectivity.

Aboard the Mars Reconnaissance Orbiter, the Shallow Radar (SHARAD) uses higher frequencies than MARSIS. Until recently, though, SHARAD’s signals couldn’t reach deep enough into Mars to bounce off the base layer of the ice where the potential water lies—meaning its results couldn’t be compared with those from MARSIS.

However, the Mars Reconnaissance Orbiter team recently tested a new maneuver that rolls the spacecraft on its flight axis by 120°—whereas it previously could roll only up to 28°. The new maneuver, termed a “very large roll,” or VLR, can increase SHARAD’s signal strength and penetration depth, allowing researchers to examine the base of the ice in the enigmatic high-reflectivity zone.

Morgan et al. examined 91 SHARAD observations that crossed the high-reflectivity zone. Only when using the VLR maneuver was a SHARAD basal echo detected at the site. In contrast to the MARSIS detection, the SHARAD detection was very weak, meaning it is unlikely that liquid water is present in the high-reflectivity zone. The researchers suggest that the faint detection returned by SHARAD under this portion of the ice cap is likely due to a localized region of smooth ground beneath the ice. They add that further research is needed to reconcile the differences between the MARSIS and SHARAD findings. (Geophysical Research Letters, https://doi.org/10.1029/2025GL118537, 2025)

—Rebecca Owen (@beccapox.bsky.social), Science Writer

Citation: Owen, R. (2025), Maybe that’s not liquid water on Mars after all, Eos, 106, https://doi.org/10.1029/2025EO250437. Published on 21 November 2025. Text © 2025. AGU. CC BY-NC-ND 3.0
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