EOS

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

In near-Earth space, charged particles and plasma waves can exchange energy most effectively through resonance. Cyclotron resonance is one such interaction, where particles whose gyromotion synchronizes with the wave fields can gain or lose energy from waves, influencing phenomena such as the radiation belts, auroras, and space weather effects that can affect satellites and communication systems.

Li et al. [2026] explore the particular conditions leading to anomalous resonance, which occurs when cyclotron resonance is altered by very large amplitude of plasma waves. The distinguishing contribution of the study is the exploration of anomalous resonance in realistic inhomogeneous environments. The results prove that the interplay of resonances may give rise to an inhomogeneity-driven pathway for energy redistribution across a broader energy range than previously recognized. The above findings provide new insights into a fundamental and previously underappreciated mechanism shaping plasma dynamics across a wide range of space and astrophysical systems.

Ion and electron trajectories in wave field without (left column) and with (right column) background inhomogeneity. Panels (a) and (c) show the trajectories of high- and low-energy ions, respectively, in a uniform background. In panels (b) and (d), the corresponding trajectories are shifted by the background magnetic-field inhomogeneity. This inhomogeneity breaks the trajectory symmetry, enabling a net wave–particle energy transfer. Panels (e) and (f) show the trajectories of low-energy electrons, which are hardly affected by the background inhomogeneity. ζ is the gyro-phase difference between the particle’s perpendicular velocity and the wave magnetic field, and dζ/dt is its rate of change. Credit: Li et al. [2026], Figure 5

Citation: Li, J.-H., Zhou, X.-Z., Wang, S., Liu, Z.-Y., Khotyaintsev, Y. V., Graham, D. B., et al. (2026). Bidirectional energy transfer via simultaneous wave-particle resonances in inhomogeneous space plasmas. AGU Advances, 7, e2026AV002479. https://doi.org/10.1029/2026AV002479

—Alberto Montanari, Editor-in-Chief, AGU Advances

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A new study provides a fascinating insight into the patterns of landslide exposure in the United States.

The increased focus in recent years on the socio-economic aspects of landslides has been welcome. This area of understanding has lagged behind that for other hazards, possibly in part because of the lack on interest from the insurance industry. Increasing evidence of the societal cost of landslides, for example in New Zealand, is shifting the focus.

A really interesting open access paper (Acosta-Reyes et al. 2026) has just been published in the AGU journal Earth’s Future that examines societal exposure to landslides in the United States. This has been reported by some parts of the mainstream media too, which is welcome given that this is a fascinating study.

This study is underpinned by the landslide susceptibility map for the United States developed by the USGS. Acosta-Reyes et al. (2026) have then combined this with two other datasets – an inventory of buildings (the U.S. Army Corps of Engineers (USACE) National Structure Inventory), which includes 128 million structures, and a national scale social vulnerability dataset (the Social Vulnerability Index).

The headlines from the study are important. Whilst terrain with high landslide susceptibility covers 19% of the land area of the United States, only 2% of the population resides within these areas (although this still represents 6.5 million people).

There is huge richness in this study, but allow me to focus on just two elements. First, this map shows the population exposure to high landslide susceptibility:-

Population exposure to high landslide susceptibility in the United States from Acosta-Reyes et al. (2026). Original caption: “National distribution of population exposure to high landslide susceptibility. Building-level LED population estimates aggregated to the census tract level. Map projected in Albers Equal Area Conic (EPSG:5070); Alaska and Hawaii are displaced from their geographic locations for visualization, with Alaska displayed at 50% of native scale.”

This shows that the most exposed populations are in the Appalachian Highlands and in the Pacific Mountain System, with more isolated areas of higher exposure elsewhere across the country.

Second, we know well that poverty greatly increases the potential human outcomes of geophysical hazards – poorer people suffer more from natural hazards. So this map is absolutely fascinating and very important:-

Poverty characteristics of the population exposed to high landslide susceptibility in the United States from Acosta-Reyes et al. (2026). Original caption: Income and poverty characteristics of the population exposed to high landslide susceptibility at the census-tract scale. (a) … (b) High-exposure population residing in tracts with poverty rates of 20% or higher. Insets for Alaska and Hawaii use a modified scale and geographic displacement for visual clarity.

There are 732,000 individuals represented in this map, but the population is hugely concentrated in the southern Appalachians. These are comparatively poor rural communities. Globally, measures to address this exposure to landslides rarely focuses on these communities, but they are so very important.

Acosta-Reyes et al. (2026) consider carefully the policy implications of these highly exposed communities living in poverty:

“Addressing these conditions requires combining hazard mitigation with broader resilience investments: early warning systems tied to precipitation forecasts can reduce harm during extreme rainfall events; temporary relocation services provide immediate protection during acute hazard periods; and for exposed households in high-risk terrain, voluntary property acquisition programs (such as FEMA’s Hazard Mitigation Grant Program) offer a long-term strategy to permanently reduce exposure, an approach already applied in parts of Appalachia for flood hazard with demonstrated benefit-cost ratios … These communities typically lack the local fiscal capacity to implement mitigation measures independently, and without sustained federal and state investment, the gap between exposure and adaptive capacity will remain.”

Translating this into policy change is very difficult, but we now have the information that highlights the need for action.

Reference

Acosta-Reyes, D. et al. 2026. Landslide exposure in the United States. Earth’s Future, e2026EF008622. https://doi.org/10.1029/2026EF008622Digital Object Identifier (DOI)

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Luckily for Heather Lynch, Adélie penguins eat mostly two things: fish and krill. Krill have a distinct pink color that penguin poop retains. And penguins form colonies, meaning that together, they produce “absolutely prodigious quantities of guano,” she said.

To put it simply: We can see penguin poop from space.

A new study, published in Current Biology, uses satellite imagery of Adélie penguin guano to track how penguin diets and populations have shifted as sea ice in Antarctica has declined. The method has “totally opened our eyes to what’s going on across the continent,” said Lynch, an ecologist at Stony Brook University and coauthor of the new study.

“Linking diet to sea ice dynamics and population change is a key piece in the puzzle of how environmental change will influence the Southern Ocean ecosystem,” Alexandra Strang, a doctoral candidate at the University of Canterbury in New Zealand who was not involved in the new research, wrote in an email. Strang studies population changes in Adélie penguins using satellite imagery.

Guano Sleuths

“The satellite archive is like a time machine for Antarctica, so we can look at not just what penguins are eating now, but also what they were eating all the way back to the earliest days of the Landsat satellite program.”

To parse out trends in Adélie penguin diets, Lynch and the research team first needed to determine whether satellite imagery could reliably capture actual differences in guano content and color. To do this, they analyzed the spectral signal (a quantitative measure of color) and nitrogen isotope content (an indicator of the types of prey present in guano) of 103 guano samples that had been collected from 16 breeding colonies on the Antarctic Peninsula.

Next, they analyzed daytime images of Antarctica from 1984 to 2013 captured by the Landsat program, a joint NASA–U.S. Geological Survey satellite program that has provided continuous images of Earth since 1972. The Landsat images allowed researchers to find penguin breeding colonies and their respective piles of colorful poop. Then, the team compared those images to sea ice data, also collected via satellites, from the National Snow and Ice Data Center that showed where sea ice in Antarctica is declining.

This Landsat satellite image of Adélie penguin colonies in the Danger Islands off the Antarctic Peninsula, taken on 22 January 2023, shows how penguins can color islands pink with their guano. Credit: NASA

“The satellite archive is like a time machine for Antarctica, so we can look at not just what penguins are eating now, but also what they were eating all the way back to the earliest days of the Landsat satellite program,” Lynch said.

The researchers found that penguin colonies in West Antarctica tended to eat diets higher in krill, while colonies in East Antarctica had diets higher in fish. They also found that diet was linked to population changes: Penguin colonies with diets higher in krill were more likely to have declining populations over the long term when compared to colonies with diets higher in fish. Decreased sea ice was associated with diets higher in krill as well.

Such patterns are an indicator that ecosystems in the Southern Ocean are changing in ways scientists should “probably understand better,” Lynch said.

Because of the fine temporal resolution of Landsat data—the satellites take images of each colony every 8 days—researchers were also able to identify diet patterns within years, including some that Lynch didn’t expect. She’d thought certain colonies would consistently be either krill specialists or fish specialists, but some colonies seemed to eat more krill in the summer than they did in either fall or spring.

“This rapid-repeat schedule of the Landsat program is really neat because it allows us to get week-to-week changes that we just otherwise wouldn’t have any handle on,” Lynch said.

Still, why penguins are changing their diets when sea ice melts remains uncertain. It’s possible that less sea ice alters fish populations, changing prey availability, but more research is needed, Lynch said. “That’s a question that we will hand off to our colleagues who work in the ocean.”

Big Questions, Big Data

“Getting these unbroken datasets decade after decade can be incredibly valuable, and their value plays out over time.”

Lynch said the study highlights the importance of workhorse programs like Landsat, which provide consistent information over long time periods. “Getting these unbroken datasets decade after decade can be incredibly valuable, and their value plays out over time,” she said. “It’s not always obvious—we don’t know what kinds of questions we’ll have 30 years from now [that satellites can help answer].”

Scientists are just beginning to understand the extent to which satellite imagery can be used to understand ecological changes. There is a disproportionate amount of satellite imagery of the poles compared to the rest of the globe, meaning much of what ecologists are learning about satellites’ utility is happening in Antarctica. But what scientists learn there could be applied to ecosystems elsewhere in the world, Lynch said.

Casey Youngflesh, an ecologist at Clemson University, prepares penguin guano samples for analysis. Credit: Casey Youngflesh

“Often ecological signals are masked with lots of variability or ‘noise’ and so, to detect these ecological trends, we need long-term data,” Strang wrote. “With satellite imagery, we can do this. We can access more remote locations without having to be there, whilst drawing on the locations that we do have on-the-ground data from.”

For Adélie penguins, at least, the value of satellite datasets “will accrue over time,” Lynch said, continuing to help researchers answer questions about penguin diet, prey availability, and how Antarctic ecosystems are changing. For example, she wants to continue to use Landsat data to determine whether krill fishing affects penguin diets. “Those are the kinds of questions we can start to ask now that we can measure what they’re actually eating directly.”

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

Citation: van Deelen, G. (2026), Tracking penguin poop from space reveals Antarctica’s changing ecosystems, Eos, 107, https://doi.org/10.1029/2026EO260247. Published on 29 July 2026. Text © 2026. 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 annual Asian monsoon is one of the most consequential components of the global climate system, pivotally affecting water availability, agriculture, and livelihoods for billions of people across much of East, South, and Southeast Asia. Even modest shifts in the timing or intensity of monsoon rainfall in a given location can lead to flooding, drought, and cascading socioeconomic impacts.

In 2024, for example, exceptionally heavy rains inundated large areas of eastern Bangladesh, affecting millions of people, damaging crops, and disrupting transportation and essential services. In contrast, delayed or below-average monsoon rainfall in parts of India has repeatedly reduced crop yields and strained water supplies, illustrating how both excess and deficient rainfall can have far-reaching consequences for food security and regional economies.

Despite decades of research, predicting the Asian monsoon’s variability from place to place and year to year remains difficult.

Despite decades of research into the complex interplays of tropical ocean conditions, land-atmosphere feedbacks, and large-scale circulation that drive the monsoon, predicting its variability from place to place and year to year remains difficult.

Traditionally, scientists have focused on studying tropical drivers such as the El Niño–Southern Oscillation (ENSO) and Indian Ocean variability. Increasingly, however, attention is turning toward processes far outside the tropics. Rapid environmental change in the Arctic, particularly the decline of sea ice, is emerging as a potential contributor to atmospheric variability that may extend into monsoon regions.

The Arctic is warming nearly 4 times faster than the global average, a phenomenon known as “Arctic amplification.” And since satellite observations of Arctic sea ice began in 1979, summer (minimum) sea ice extent has declined sharply—by about 12% per decade—exposing larger expanses of ocean surface, which absorbs more solar radiation than ice does, and accelerating regional warming [Screen and Simmonds, 2010; Serreze and Barry, 2011].

Arctic sea ice extents and concentrations have declined substantially in recent decades. The minimum ice extent in 2024, shown here, covered far less area compared with the 1981–2010 median. Credit: NOAA Climate.gov image, based on data from the National Snow and Ice Data Center

These changes are often framed as primarily polar concerns, but a growing body of research suggests they may also influence atmospheric circulation patterns affecting distant regions, including the Asian monsoon.

Arctic Amplification and the Jet Stream

Arctic amplification, driven largely by sea ice loss and albedo feedbacks [Screen and Simmonds, 2010; Serreze and Barry, 2011], reduces the equator-to-pole temperature gradient, a key driver of midlatitude atmospheric circulation. This effect has motivated one of the most widely discussed hypotheses about modern climate dynamics: that Arctic warming alters the behavior of the jet stream in ways that affect weather and climate at lower latitudes [Francis and Vavrus, 2012, 2015].

The hypothesis proposes that a weaker meridional (north–south) temperature gradient leads to reduced zonal (west–east) wind speeds and increased meridional meandering of the flow of the jet stream. In this framework, a “wavier” jet stream favors more persistent ridges and troughs, potentially allowing high-latitude weather anomalies to propagate into Eurasia and influence subtropical systems.

Though influential, this idea is far from settled. Subsequent studies have both supported and challenged different aspects of the hypothesis. Some observational analyses, for example, have suggested that episodic increases in the jet stream’s wave amplitude and the frequency of blocking events (stationary high-pressure systems that block other weather systems from moving through an area) are consistent with a weakened jet [Francis and Vavrus, 2015; Coumou et al., 2018]. Others, however, have found that internal atmospheric variability or forcing by tropical conditions alone can explain much of the jet stream’s observed behavior without requiring a prominent Arctic contribution [Barnes and Screen, 2015; Blackport and Screen, 2020].

Unraveling the nuanced cause-and-effect relationships between the Arctic and the jet stream is essential for interpreting potential downstream effects on the Asian monsoon.

Climate model experiments have further complicated the picture. Whereas some simulations reproduce jet stream responses consistent with the Francis-Vavrus mechanism, others show weak, negligible, or even opposite responses. These discrepancies arise in part because modeled atmospheric responses to Arctic forcing are sensitive to background conditions, including sea surface temperatures, stratospheric variability, and how transient eddies in the atmosphere are represented.

Meanwhile, synthesis studies have emphasized that Arctic amplification does not seem to produce a robust, uniform response in the jet stream. Instead, its influence appears to depend on season, region, and interaction with other climate drivers. In this view, Arctic change may alter the likelihood of certain circulation regimes, such as blocking patterns, occurring at given times and places, rather than causing lasting, systematic shifts.

Unraveling the nuanced cause-and-effect relationships between the Arctic and the jet stream, as a large body of recent research has aimed to do, is essential for interpreting potential downstream effects on the Asian monsoon.

Emerging Evidence of a Complex Connection

Recent studies have begun to investigate Arctic-monsoon linkages explicitly, though their results also reveal a complex picture.

Duo and Zhang [2025] used a combination of observational datasets and climate model simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to examine late-season (autumn) monsoon dynamics over Southeast Asia. Their analysis showed that reduced Arctic sea ice is associated with delayed monsoon retreat and increased rainfall during the postmonsoon transition, which the researchers attributed to Arctic-induced circulation changes weakening zonal winds and enhancing moisture convergence over Southeast Asia. Their results highlight that Arctic forcing may influence not only seasonal precipitation averages but also monsoon timing.

Zhang et al. [2024] used reanalysis data alongside coupled climate model experiments from the Polar Amplification Model Intercomparison Project (part of CMIP6) to explore interdecadal variability in the East Asian summer monsoon. They found that Arctic sea ice loss can generate stationary wave responses across Eurasia that alter circulation in the upper troposphere and modulate monsoon strength and rainfall distribution. Their simulations also suggested that Arctic forcing contributes to longer-term variability in monsoon circulation and rainfall that is superimposed on anthropogenic warming trends.

Recent studies indicate that declining Arctic sea ice does not trigger a uniform monsoon response.

In other work, Sardana and Agarwal [2025] examined the influences of spring sea ice variability in the Barents and Kara Seas on the Indian summer monsoon using 6 decades of observational data. They reported that reduced sea ice in the Barents-Kara region is associated with suppressed rainfall over northern India, proposing that the shortage of sea ice alters large-scale atmospheric circulation patterns and weakens moisture transport into the subcontinent.

The studies above indicate that declining Arctic sea ice does not trigger a uniform monsoon response. Whereas Duo and Zhang [2025] identified enhanced late-season rainfall as a result of sea ice loss, Sardana and Agarwal [2025] found that it suppressed monsoon rainfall. Zhang et al. [2024], meanwhile, showed that Arctic sea ice loss modulates long-term variability in the East Asian summer monsoon rather than producing a consistent increase or decrease in monsoon rainfall.

These differences likely arise because of the different regions, seasonal timings, and teleconnection pathways considered in each study. Rather than contradicting one another, however, the studies collectively suggest that Arctic influences on the Asian monsoon are spatially and temporally heterogeneous.

How Arctic Signals Travel South

In addition to outlining monsoon effects associated with Arctic sea ice loss, recent research has proposed several mechanisms to explain physically how ice loss may influence storm systems thousands of kilometers away (Figure 1).

Fig. 1. Arctic sea ice loss may be linked to Asian monsoon variability in a variety of ways, including those illustrated here. Declining sea ice enhances Arctic amplification and weakens the equator-to-pole temperature gradient, altering the jet stream’s structure, the propagation of Rossby waves, and land temperatures across Eurasia. These atmospheric adjustments may then influence the timing, intensity, and spatial distribution of Asian monsoon rainfall, including delaying monsoon retreat. Credit: Neha Kushwaha

Jet stream modulation is one possible mechanism. As noted earlier, Arctic amplification can alter atmospheric temperature gradients and the strength and structure of the polar jet stream. A wavier jet may favor persistent ridges and troughs over Eurasia that can promote the divergence of winds in upper atmospheric layers, as well as vertical motion and moisture transport relevant for monsoon dynamics [Serreze and Barry, 2011].

The propagation of Rossby waves, large-scale atmospheric waves driven by Earth’s rotation, is another potential mechanism. Changes in heat fluxes and pressure-temperature conditions (i.e., geopotential heights) over the Arctic surface may excite stationary Rossby wave trains that propagate into Eurasia. These wave trains can reorganize subtropical high-pressure systems and monsoon troughs, thereby affecting atmospheric convection and rainfall distribution [Zhang et al., 2024; Duo and Zhang, 2025].

Land-atmosphere feedbacks, including Arctic-induced circulation changes, can enhance warming over Eurasia, particularly during spring. This warming may modify land-sea thermal contrasts, a key driver of monsoon circulation. Changes in snow cover and soil moisture can amplify or dampen these contrasts, introducing additional regional variability [Serreze and Barry, 2011; Zhang et al., 2024].

An emerging line of research suggests that Arctic variability may also influence monsoons indirectly via the stratosphere. Sea ice loss can modify the flux of Rossby waves entering the stratosphere, potentially weakening the polar vortex. The resulting atmospheric circulation anomalies can propagate downward from the stratosphere into the troposphere and affect midlatitude circulation patterns that govern monsoon systems [Barnes and Screen, 2015].

The effects of transient eddies in the atmosphere add additional complexity. Changing Arctic temperature gradients can modify eddy formation, influencing how energy is transferred and, in turn, affecting both large-scale wave patterns and the growth and decay of synoptic weather systems that contribute to monsoon variability.

Limitations on Current Understanding

The Arctic-monsoon connection does not occur via a single linear pathway but through a network of interacting atmospheric processes operating across scales.

The variety of mechanisms above demonstrates that the Arctic-monsoon connection does not occur via a single linear pathway but through a network of interacting atmospheric processes operating across scales. Despite growing interest in this connection, substantial uncertainties remain regarding the relative importance and robustness of different mechanisms and their specific effects on the Asian monsoon. Resolving these uncertainties is not an easy problem to parse.

Tropical drivers such as ENSO continue to dominate interannual monsoon variability, often overshadowing the effects of high-latitude influences [Turner and Annamalai, 2012]. Furthermore, observational records of Arctic sea ice and its relationship with Asian monsoon variability are relatively short compared to the timescale of Arctic change, limiting our ability to detect robust, long-term relationships [Barnes and Screen, 2015].

Studies using climate models show considerable spread in monsoon responses to Arctic forcing. Differences in model resolution and representations of sea ice and atmospheric dynamics lead to varying outcomes, including in the magnitude and even direction of monsoon responses.

Another key uncertainty lies in the timescales of responses. Although some studies identify interannual links between Arctic variability and monsoon behavior, others emphasize decadal or longer-term modulation [Zhang et al., 2024; Sardana and Agarwal, 2025]. This distinction raises an important question: Are observed relationships indicative of a persistent physical connection, or do they emerge intermittently under favorable background conditions? Addressing this question will require the availability of longer observational records and conducting targeted model experiments designed to isolate the effects of Arctic forcing.

Furthermore, interactions between Arctic and tropical drivers remain poorly constrained. For example, Arctic-induced atmospheric circulation anomalies may reinforce or counteract ENSO-related patterns. This nonlinearity complicates attribution and suggests that Arctic influences are best understood within a multidriver framework, rather than in isolation.

Why This Matters in a Warming World

Understanding Arctic-monsoon teleconnections is not merely an academic exercise; rather, it carries significant implications. The monsoon underpins food security, water resources, and economic stability across much of Asia. If changing Arctic conditions influence background atmospheric states, they may undermine these crucial needs by affecting the likelihood and timing of rainfall and drought, including extreme events.

Ice loss may act as a risk amplifier, subtly reshaping the conditions under which monsoons evolve.

Although current evidence does not support a simple causal chain between Arctic sea ice decline and effects on the Asian monsoon, ice loss may act as a risk amplifier, subtly reshaping the conditions under which monsoons evolve. As Arctic warming continues and the region undergoes further rapid transformation, whether and how these teleconnections could strengthen and interact with other climate drivers in complex ways remain open questions.

Recognizing these connections challenges the traditional view of monsoons as purely tropical systems and highlights the need for a hemispheric perspective in climate research and prediction. Improving seasonal forecasting, refining climate projections, and anticipating extreme events will increasingly require accounting for cross-latitude interactions.

The Arctic-monsoon connection ultimately illustrates a broad principle: Climate change is not simply a collection of independent regional trends, but a global network of linked processes. Understanding these links is essential for managing risk in a world where distant changes can have local consequences.

References

Barnes, E. A., and J. A. Screen (2015), The impact of Arctic warming on the midlatitude jet-stream: Can it? Has it? Will it?, Wiley Interdiscip. Rev. Clim. Change, 6(3), 277–286, https://doi.org/10.1002/wcc.337.

Blackport, R., and J. A. Screen (2020), Insignificant effect of Arctic amplification on the amplitude of midlatitude atmospheric waves, Sci. Adv., 6(8), eaay2880, https://doi.org/10.1126/sciadv.aay2880.

Coumou, D., et al. (2018), The influence of Arctic amplification on mid-latitude summer circulation, Nat. Commun., 9(1), 2959, https://doi.org/10.1038/s41467-018-05256-8.

Duo, Y., and J. Zhang (2025), Arctic ice loss is delaying monsoon retreat over the Indochina Peninsula, npj Clim. Atmos. Sci., 8, 364, https://doi.org/10.1038/s41612-025-01241-3.

Francis, J. A., and S. J. Vavrus (2012), Evidence linking Arctic amplification to extreme weather in mid-latitudes, Geophys. Res. Lett., 39(6), L06801, https://doi.org/10.1029/2012GL051000.

Francis, J. A., and S. J. Vavrus (2015), Evidence for a wavier jet stream in response to rapid Arctic warming, Environ. Res. Lett., 10(1), 014005, https://doi.org/10.1088/1748-9326/10/1/014005.

Sardana, D., and A. Agarwal (2025), Impact of spring sea ice variability in the Barents-Kara region on the Indian summer monsoon rainfall, Sci. Rep., 15, 37790, https://doi.org/10.1038/s41598-025-21544-y.

Screen, J. A., and I. Simmonds (2010), The central role of diminishing sea ice in recent Arctic temperature amplification, Nature, 464, 1,334–1,337, https://doi.org/10.1038/nature09051.

Serreze, M. C., and R. G. Barry (2011), Processes and impacts of Arctic amplification, Global Planet. Change, 77, 85–96, https://doi.org/10.1016/j.gloplacha.2011.03.004.

Turner, A. G., and H. Annamalai (2012), Climate change and the South Asian summer monsoon, Nat. Clim. Change, 2(8), 587–595, https://doi.org/10.1038/nclimate1495.

Zhang, X., et al. (2024). The role of Arctic sea ice loss in the interdecadal trends of the East Asian summer monsoon in a warming climate, npj Clim. Atmos. Sci., 7, 174, https://doi.org/10.1038/s41612-024-00717-y.

Author Information

Neha Kushwaha (neha24@iiserb.ac.in), Indian Institute of Science Education and Research Bhopal, India

Citation: Kushwaha, N. (2026), Arctic sea ice loss may be reshaping the Asian monsoon, Eos, 107, https://doi.org/10.1029/2026EO260249. Published on 29 July 2026. Text © 2026. 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.

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

Rising atmospheric carbon dioxide (CO₂) is cooling the upper atmosphere, but it is also changing how the atmosphere responds to natural disturbances. One important example is a sudden stratospheric warming (SSW), a wintertime event that disrupts atmospheric circulation from the stratosphere to the edge of space. Because SSWs can alter the ionosphere, they can affect satellite operations, radio communications, and navigation systems.

Using a whole-atmosphere model, Kumar et al. [2026] investigate how the atmospheric response to strong SSW changes in a future climate with doubled CO₂. They find that CO₂-driven cooling changes upper-atmosphere winds, making the response increasingly different between the Northern and Southern Hemispheres. These changes produce larger hemispheric differences in atmospheric composition and ionospheric plasma density. The study provides new insight into how climate change could influence future space weather and its impacts on modern technology.

Citation: Kumar, S., Oberheide, J., & Martinez, B. C. (2026). Impact of doubled CO2 on the response of the mesosphere, thermosphere, and ionosphere to the 2008–2009 sudden stratospheric warming. Geophysical Research Letters, 53, e2026GL121817. https://doi.org/10.1029/2026GL121817  

—Huixin Liu, Editor, Geophysical Research Letters

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In June 2026 I recorded 48 fatal landslides causing 131 fatalities. 2026 continues to be atypical in terms of the temporal pattern of fatal landslides.

This is my regular update for the number of fatal global landslides, focusing on June 2026. As usual, this data has been collected in line with the methodology described in Froude and Petley (2018) and in Petley (2012). References are listed below – please cite these articles if you use this analysis. Data presented in these updates should be treated as being provisional at this stage as I will reanalyse them prior to formal publication, and other events will emerge.

Note that this data excludes landslides triggered by earthquakes.

The headline figures are as follows:

June 2026: 48 fatal landslides causing 131 fatalities.

This is the number of landslides by month in 2026 to the end of June:-

The number of global fatal landslides in 2026 by month to the end of June.

Last month I once again noted that 2026 was proving to be atypical in terms of the pattern of fatal landslides. This has continued through June, with the total number recorded in this month once again being lower than for both February and March. It is surprising that the June total is lower than that of May, as well. We would normally expect to see the monthly landslide total increasing from April through to July. This may indicate that patterns of rainfall this year are varying from the norm. More research is needed.

My preferred way of presenting this data us to use the cumulative total by pentad. This graph is to pentad 30, which captures all of the June data:-

The cumulative total number of global fatal landslides in 2026 by pentad to the end of June.

The shows that the number of fatal landslides in 2026 continues to run way ahead of the long term mean, and within noise was equivalent to the exceptional year of 2024 (albeit with a different temporal pattern).

The end of June marks the start of the Northern Hemisphere monsoon season, and the uptick in the number of recorded landslides is clear in the graph. It will be interesting to see the July data as the monsoon gets into full swing.

I hope to be able to produce the July 2026 data next week.

References

Froude, M. and Petley, D.N. 2018.  Global fatal landslide occurrence from 2004 to 2016.  Natural Hazards and Earth System Sciences 18, 2161-2181.

Petley, D.N. 2012. Global patterns of loss of life from landslides. Geology 40 (10), 927-930.

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In August of 2020, intense winds accompanied a severe thunderstorm that ripped through the Great Plains. Gusts up to 100 miles (160 kilometers) per hour produced 26 tornadoes, destroyed crops, took roofs off houses, knocked out power, and killed four people.

The storm was a derecho—a fast-moving, destructive windstorm that forms under unique conditions.

Radar shows the 10 August 2020 derecho at 1-hour time steps as it moved across the Plains and Midwest states. Credit: NOAA/NWS

Scientists track extreme weather phenomena like tornadoes, hurricanes, and derechos in detail to aid in forecasting and communication to the public. But definitions for derechos have always varied, and a comprehensive inventory of them had never existed, until now. A new study, published in the Bulletin of the American Meteorological Society, presents the country’s first archive of derechos, offering scientists a better opportunity to understand the drivers behind these destructive storms.

“We’re trying to objectively identify these events,” said Brian Squitieri, lead author of the new study and a meteorologist at NOAA’s Storm Prediction Center.

Assembling an Archive

“For a long time, meteorologists have taken the approach of ‘It’s hard to define a derecho, but I know one when I see one.’”

The definition of the term “derecho” has been difficult for scientists to pin down: “For a long time, meteorologists have taken the approach of ‘It’s hard to define a derecho, but I know one when I see one,’” said Michael Coniglio, a meteorologist at NOAA’s National Severe Storms Laboratory who was not involved in the new study.

In a 2025 paper, Squitieri and others put forth a new definition of the term that required a windstorm to meet strict requirements for wind gusts and develop from a “cold pool-driven mesoscale convective system” (MCS)—a specific type of thunderstorm cluster resulting from a collection of cold air.

Creating an archive of derechos required applying this new definition to past events. Squitieri ensured that the criteria focused on the distinct physical atmospheric processes that lead to a derecho, rather than “just any large-scale thunderstorm wind event,” he said.

With their criteria in hand, the research team analyzed 2 decades’ worth of detailed data from the Next Generation Weather Radar (NEXRAD) system, operated by the National Weather Service, the Federal Aviation Administration, and the U.S. Air Force. Within the NEXRAD data (1996–2025), they found 96 definitive derechos and 13 likely derechos.

Prior to the NEXRAD era, NOAA used hand-drawn paper maps to summarize radar data and collected storm reports in various formats. Squitieri and the research team combed through more than 2,000 paper maps and more than 22,500 storm reports to identify likely past derechos dating back to 1955. Still, without NEXRAD data, none of the likely derechos from 1955 to 1995 could fully fulfill the team’s criteria. Instead, they identified 48 likely derechos and 16 possible derechos.

“There have been lots of attempts at this over the years,” Coniglio said. The new study, he said, “is an incredibly detailed and thorough paper that I think is now the definitive piece of research that we have out there to know if something is a derecho or not.”

Derecho Behavior

From the new archive, the researchers were able to distinguish patterns in derecho behavior in the United States. The archive confirmed that derechos typically form in three corridors: the Midwest/Ohio Valley, the Northern Plains, and the Southern Plains.

The team also noticed the impressive impact of derechos in the data. “There are a lot of common factors that seem to stick out in reports [of derechos] that are a little bit more unique than what you see with a lot of other wind events,” Squitieri said.

In particular, the identified derechos had large, long-lasting effects on communities, sometimes being responsible for dozens of deaths or leaving towns without power for days. In many cases, derechos caused the worst power outages in a town’s or region’s history. “That’s quite a title for derechos to compete with, but some have achieved that,” Squitieri said.

Satellite imagery shows the 20 June 2025 derecho moving across North Dakota. Credit: CSU/CIRA & NOAA

Some written reports of derechos compared the destruction left in their wake to the effects of hurricanes. Squitieri emphasized that just because a certain windstorm doesn’t meet the derecho criteria doesn’t mean it’s not dangerous and that plenty of windstorms that are not derechos still have tremendous impacts.

Future Forecasts

The derecho archive is another step in NOAA’s goals of ultimately being able to better forecast derechos and better communicate derecho risk to the public. Scientists can use the archive to assess what conditions seem to be present for the formation of derechos compared to other wind events.

“We might be able to cue in on a clue for these higher-impact events more cleanly,” Squitieri said.

“Classifying these things ahead of time can help [meteorologists] understand what to look for and what to communicate to the public.”

The Storm Prediction Center has already begun to study the ambient environments that seem to create derechos to parse out signals that forecasters could use, with promising results, he added.

NOAA is also working to develop a MCS wind swath classification system similar to the Saffir-Simpson Hurricane Wind Scale to help forecasters communicate the risk of wind events to the public. This scale would classify all MCS wind swaths into two types: squall-line wind swaths and those driven by cold pools. Squitieri imagines that a 4 or 5 on the cold-pool-driven scale would be a derecho or “super derecho,” respectively, and lower numbers would be used to describe the risks posed by less severe storms. He hopes that such a scale would be operational sometime in 2027 or 2028.

“Classifying these things ahead of time can help [meteorologists] understand what to look for and what to communicate to the public,” Coniglio said.

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

Citation: van Deelen, G. (2026), What drives derechos? The first derecho archive could help meteorologists figure it out., Eos, 107, https://doi.org/10.1029/2026EO260245. Published on 28 July 2026. Text © 2026. 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: Machine Learning and Computation

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

单个地震仪通常不足以可靠地探测地震或地下核试验等人类活动。因此，研究人员通常会结合分布在小范围地理区域内的多个地震仪的读数，来提高分析的可靠性。Köhler 等人的一项新研究表明，人工智能 (AI) 可以比传统技术更有效地整合来自多个传感器的读数，从而更可靠地探测微弱的地震信号。

研究人员利用挪威地震研究基金会 NORSAR和其他运营商运营的地震阵列 30 年的观测数据，并通过三种不同的方式训练了一个 AI 模型来探测地震信号。首先，他们每次使用一个台站的数据训练模型，然后应用该模型并将每个台站的结果合并。其次，他们使用传统技术合并同一阵列中多个传感器的信号，然后使用来自多个台站的这些合并信号训练模型。第三，他们将来自所有阵列台站的所有数据都提供给模型，让模型自行决定如何合并这些数据。

第二种方法（训练前合并信号）能够放大微弱信号，其信号检测精度在三种方法中最高。同时，第三种模型（由模型自行决定如何合并台站数据）是计算效率最高的策略，其精度介于其他两种方法之间。

考虑到需要在精度和速度之间取得平衡，研究人员建议在进行实时监测时由模型自行决定如何合并数据，而在可以接受较慢速度的情形中，可以在应用模型之前或之后合并数据。

然而，由于使用区域性有限的训练数据集，该模型对训练区域之外的区域泛化能力较差。若能使用全球数据进行训练，有望改进结果。这一问题主要出现在S波检测中，在P波检测的泛化能力方面则未出现类似问题。

总体而言，结果表明，人工智能可以通过帮助研究人员检测地震、地下核试验和其他地震活动中难以识别的微弱信号来提升地震监测能力。(Journal of Geophysical Research: Machine Learning and Computation, https://doi.org/10.1029/2026JH001249, 2026)

—科学撰稿人Saima May Sidik (@saimamay.bsky.social)

This translation was made by Wiley. 本文翻译由Wiley提供。

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

Unlocking the physics of natural and induced earthquakes remains a major challenge. Gischig et al. [2026] performed the “Mzero” hydraulic stimulation experiments within the BedrettoLab, which aimed to find a stimulation procedure to enhance seismicity up to an induced moment magnitude (Mw) 0 earthquake. The multi-sensor network enabled detailed measurements of pressure, fluid flow, and deformation during the stimulations. Some experiments were conducted in a pre-conditioned rock mass, where fluids had previously been injected at pressures just below the fault reactivation threshold.

The results show that earthquake evolution, migration, and magnitude strongly depend on both the injection procedure and the site’s stimulation history. Pre-conditioning induced a mainshock-aftershock sequence and altered rock deformation and fluid flow patterns. In contrast, experiments without pre-conditioning produced no mainshock but exhibited higher seismicity rates and more pronounced outward migration of micro-earthquakes.

These findings are highly relevant for developing strategies to mitigate or even suppress injection-induced felt earthquakes in geo-energy applications.

Citation: Gischig, V. S., Meier, M.-A., Lambiase, A., Jiang, D., Hertrich, M., Gholizadeh Doonechaly, N., et al. (2026). Hydraulic stimulation experiments attempting to enhance induced seismicity for earthquake physics research. Journal of Geophysical Research: Solid Earth, 131, e2026JB033768. https://doi.org/10.1029/2026JB033768

—Birgit I. Mueller, Associate Editor, JGR: Solid Earth

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Satellite images show two very large landslides and multiple smaller failures, and channelised debris flows, in Shimen County in China.

In China, this year rainy season started with an intense event that covered the provinces of Guizhou, Hubei and Hunan in the period between 17 and 21 May 2026. There were some news reports at the time, although the story disappeared quite quickly. One area that was seriously affected was Enshi Tujia and Miao autonomous prefecture, which I have highlighted previously.

However, news reports also suggested a major impact in Shimen County in Hunan Province, which impacted 23 townships with 103,247 residents were affected. One news report indicates that about 340 mm of rain fell in 24 hours. There was some imagery of the aftermath of landslides. One article from Hong Kong reports 16 dead and missing in this area.

Planet Labs has now managed to capture some good imagery of the aftermath of the rainfall event in Shimen County. The area affected is around: [29.9428, 110.5510]. Planet Labs captured an image on 27 June 2026 using their PlanetScope instruments:-

Planet Labs image of the May 2026 landslides in Shimen County, China. Image copyright Planet Labs, used with permission, draped onto the Google Earth DEM.

There are two very large landslides in the image (and highlighted below). The one with the marker is about 3.5 km from the crown to the main drainage line, although one could argue that the runout distance is about another kilometre beyond that point. Note that the image shows that this landslide was valley-blocking and that a small lake has developed. There is a Sentinel image from 23 July 2026 that shows that this lake was still intact.

Planet Labs image of one of the May 2026 landslides in Shimen County, China. Image copyright Planet Labs, used with permission, draped onto the Google Earth DEM.

The other large landslide, also seen in the above image, is about 3 km long and 450 m wide. Elsewhere there are many smaller landslides, although some of these are over a kilometre in length:-

Planet Labs image of the smaller May 2026 landslides in Shimen County, China. Image copyright Planet Labs, used with permission, draped onto the Google Earth DEM.

It is notable that these landslides have generated very serious channelised debris flows in the main drainage lines, which appear to have extended over a distance of many kilometres. There is evidence of severe damage to the infrastructure in the channels.

This intense cluster of landslides occurs in an area of about 20 km x 7 km. Clearly, in this zone there must have been very exceptional rainfall, greater than in adjacent areas.

Acknowledgement

Many thanks to Planet Labs for use of the imagery.

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

It is always encouraging when a new study improves our understanding of a process or compartment within the global nitrogen (N) cycle. This is certainly the case of the recently published study by Langley et al. [2026].

Drawing on an extensive dataset comprising of 8,012 soil N measurements from 255 tidal wetlands, including both salt marshes and mangroves, the authors show that these ecosystems act as important sinks for nitrogen. This stored nitrogen, referred to as blue nitrogen, is buried alongside carbon in wetland soils (see figure above).

The study estimates that tidal wetlands account for approximately 13-15% of marine nitrogen burial, highlighting their role as major hotspots of N accumulation in coastal environments. By retaining nitrogen that would otherwise be transported to adjacent waters, these ecosystems help mitigate harmful environmental impacts such as eutrophication, toxic algal blooms, and water quality degradation.

However, the capacity of tidal wetlands to provide this valuable ecosystem service is increasingly threatened by human-driven environmental change. Rising sea levels may enhance nitrogen sequestration in some wetlands, but only where these ecosystems can persist. If wetlands are degraded or lost, the consequences could be severe. Rather than functioning as N sinks, they may become net sources of N, releasing previously stored N back into aquatic systems and exacerbating the very problems they currently help to alleviate. Thus, conserving and restoring tidal wetlands is essential, not only for blue carbon storage, but also for maintaining their critical role in regulating the coastal nitrogen cycle.  

Citation: Langley, J. A., Chapman, S. K., Wang, L., Maxwell, T. L., Rivera, P., Adame, M. F., et al. (2026). Blue nitrogen follows the fate of tidal wetlands. Earth’s Future, 14, e2025EF006747. https://doi.org/10.1029/2025EF006747

—Luis Lassaletta, Associate Editor, Earth’s Future

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Editors’ Vox is a blog from AGU’s Publications Department.

Sand and gravel mined from riverbeds serve as essential raw materials for concrete, asphalt, and other construction materials across the world. But the processes of extracting these critical natural resources have serious environmental and ecological consequences.

A new article in Reviews of Geophysics examines where and how much sand and gravel are mined across the world, and the environmental and societal impacts. Here, we asked the authors to give an overview of sand and gravel mining, the challenges of studying the impacts, and what questions remain.

What are the primary uses of river sand and gravel?

River sand and gravel are the most heavily mined solid materials globally.

River sand and gravel, collectively known as aggregates, are the most heavily mined solid materials globally, serving as the literal backbone of modern urban infrastructure and economic development. Their primary application is in the construction industry, where they constitute over 70% of concrete by volume, alongside applications in asphalt production and building foundations.

River sand is uniquely prized and irreplaceable for concrete manufacturing due to its distinct, naturally weathered properties. Unlike desert sand, which is too fine and rounded, river sand possesses sharp, angular grains that provide the critical granular friction and structural bonding required for robust concrete mixes. Additionally, it is entirely non-saline, making it far superior to marine sand, which contains salts that corrode steel reinforcement structures within buildings and bridges. Beyond concrete and asphalt, massive volumes of river sand are used directly for land reclamation projects to engineer new land space in coastal cities before major building construction begins.

Where are river sand and gravel mined across the world?

Globally, total demand for sand and gravel used in concrete production reached an estimated 28.03 billion tonnes in 2024, spanning at least 65 countries that we identified through our literature review. While sand and gravel mining (SGM) is a global phenomenon, extraction activities and consumption patterns are highly unevenly distributed, with dramatic hotspots concentrated in rapidly developing regions.

Asia stood as the dominant epicentral region for aggregate demand in 2023, consuming an estimated 23.02 billion tonnes annually, driven overwhelmingly by booming urbanization and infrastructure expansion. Within Asia, China is the world’s largest consumer by a wide margin, extracting 6.07 billion tonnes of sand and 8.10 billion tonnes of gravel in a single year to support its construction sector. India ranks as the second highest global consumer, where sand mining is heavily concentrated in peninsular rivers during the dry season and gravel extraction dominates the Himalayan foothills. Vietnam is the third largest consumer globally, with intense, mechanized dredging occurring throughout the Mekong and Red River deltas.

Outside Asia, substantial and rising riverine extraction pressures are documented across Africa, particularly in Egypt, Algeria, and Nigeria, and South America, especially along large tropical systems such as the Paraná and Tocantins rivers in Brazil. Conversely, in Europe and North America, contemporary aggregate extraction has largely shifted away from active riverbeds toward marine sources, floodplain quarries, and crushed rock.

What are the environmental and ecological consequences of SGM?

The environmental and ecological consequences of sand and gravel mining are severe, cascading from localized physical disruptions into widespread ecosystem degradation.

The environmental and ecological consequences of sand and gravel mining are severe, cascading from localized physical disruptions into widespread ecosystem degradation. Instream extraction directly excavates the riverbed, creating dredge pits and other erosional features, while the resulting sediment deficit can generate a “hungry water” effect when removal exceeds natural replenishment. This imbalance promotes further riverbed incision, downstream and upstream erosion, and severe bank instability that may induce seasonal riverbank collapse. In deltas, channel deepening can allow seawater wedges to migrate farther inland, resulting in salinity intrusion that damages agricultural land and compromises freshwater security. Furthermore, vertical incision alters surface water–groundwater interactions, lowers adjacent water tables, and may impair alluvial aquifer recharge. Water quality can also deteriorate as heavy machinery and suction dredging resuspend bottom sediments, producing turbidity plumes, reducing dissolved oxygen, and potentially remobilizing sequestered contaminants, heavy metals, and excess agricultural nutrients.

Ecologically, these physical changes cause immediate habitat destruction. Benthic and macroinvertebrate communities may be buried or displaced, while critical spawning grounds for gravel-dependent fish species are removed or degraded. Together, these stressors reduce habitat complexity, alter algal and aquatic communities, and can drive broader biodiversity loss, threatening vulnerable river-dependent species and the long-term structural resilience of major river systems.

Sand and gravel mining can trigger a cascade of river-system impacts, from channel incision, bank erosion, and altered sediment transport to degraded habitats, reduced water quality, and wider risks for ecosystems and river-dependent communities. Credit: Park et al. [2026], Figure 13

Why is it challenging to study the impacts of SGM?

Studying the impacts of SGM is exceptionally challenging due to deep data scarcities, institutional opacity, and the complex biophysical scales of river networks. A primary obstacle is the severe under-reporting and prevalence of illegal mining operations; official government statistics and company reports frequently miss the true scale of extraction, with measured physical volumes often doubling or tripling officially declared numbers. Furthermore, international trade data (like the UN Comtrade database) is plagued by contradictory records between importing and exporting nations, treating sand as a homogeneous commodity while masking its exact geographic origin. Methodologically, much of the intense extraction occurs underwater, hidden from public view. Tracking these changes requires expensive, logistically demanding, and highly technical bathymetric sonar surveys that must be maintained over years to isolate mining signatures from natural seasonal erosion or the impacts of upstream dams. Finally, there is a pronounced spatial-temporal mismatch. The socio-economic demand driving SGM often originates thousands of miles away in urban centers or across international borders, while the geomorphic and ecological impacts propagate dynamically both upstream and downstream, making it difficult to establish clear, direct cause-and-effect chains for policy design.

What is the “Driver-to-Management Pathway” framework?

The “Driver-to-Management Pathway for Sustainable Sand and Gravel Mining” (DMP-SGM) framework is a comprehensive, four-stage systemic structure introduced to unify the historically fragmented scientific understanding of global extraction activities. It serves as an analytical bridge linking macro-level economic forces to local biophysical changes and regulatory responses.

The first stage, Drivers, identifies and quantifies the socio-economic and demand-side pressures fueling extraction, such as rapid urbanization, industrial production, and land reclamation. The second stage, Extent, focuses on mapping the precise spatial distribution, temporal variations, and physical magnitudes of sediment removal. The third stage, Impact, systematically examines how these physical extraction footprints alter river systems, tracing the pathways through which hydrogeomorphic changes (such as riverbed incision, turbidity plumes, and bank collapse) cascade into downstream ecological degradation and socio-economic vulnerabilities. The final stage, Management, outlines governance interventions, emphasizing the need to integrate technical work—such as real-time vessel monitoring, numerical modeling, and the mapping of Sustainable Mining Zones (SMZs)—with adaptive top-down regulations, international cross-border policies, and inclusive stakeholder engagement. This framework closes the feedback loop, ensuring policy limits are directly informed by biophysical sediment replenishment rates.

The Driver-to-Management Pathway for Sustainable Sand and Gravel Mining links the forces driving extraction to its spatial extent, environmental and ecological impacts, and possible management responses. The framework highlights where better data, monitoring, and governance are needed to support more sustainable river sand and gravel mining. Credit: Park et al. [2026], Figure 2a

What are some of the remaining knowledge gaps?

Despite an accelerating volume of research, profound knowledge gaps remain where additional scientific efforts are critically needed to guide sustainable resource management. Geographically, research remains heavily clustered around a few high-profile hotspots such as in China and Vietnam, leaving emerging mining fronts across rapidly urbanizing regions of Africa and South America largely undocumented and limiting the global transferability of management strategies. Thematically, the literature is heavily dominated by physical hydrogeomorphic perspectives. Quantitative, empirical studies that measure the direct, long-term impacts of SGM on aquatic biodiversity, food security, human health, and local livelihoods remain rare and are frequently treated as secondary components rather than primary research foci. Mechanistically, the exact thresholds and baseline rates of natural sediment replenishment are poorly constrained for most global rivers, leaving policy makers unable to establish geomorphically sustainable extraction caps.

Furthermore, additional research is urgently required to standardize remote sensing detection algorithms that can accurately track small-scale, artisanal mining operations across diverse geographic regions. Finally, a critical gap exists in understanding the compound, non-linear interactions between SGM and other systemic anthropogeomorphic stressors, such as climate change, relative sea-level rise, land subsidence, and upstream sediment trapping by hydropower dams.

—Edward Park (geo.edpark@gmail.com; 0000-0002-1299-1724), Nanyang Technological University, Singapore; and Christopher Hackney (0000-0001-5390-9136), Newcastle University, United Kingdom

Editor’s Note: It is the policy of AGU Publications to invite the authors of articles published in Reviews of Geophysics to write a summary for Eos Editors’ Vox.

Citation: Park, E., and C. Hackney (2026), The hidden costs of mining river sand, Eos, 107, https://doi.org/10.1029/2026EO265027. Published on 27 July 2026. 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 © 2026. The authors. CC BY-NC-ND 3.0
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Source: Earth and Space Science

The expansive red bluffs of Western Australia’s Yilgarn Craton give the landscape a Martian appearance. It turns out the resemblance is more than superficial: The Yilgarn Craton also shares geological characteristics with lakes in Mars’s Terra Sirenum region. Plattner et al. recently characterized those shared features to shed light on the region’s aqueous history and its potential to have supported life.

The Yilgarn Craton contains thousands of acidic and saline lakes that undergo repeated wet-dry cycles. The researchers sampled 40 lakes during both the wet and dry seasons to assess how they change through time. These extreme environments are shaped by the interplay of groundwater, evaporation, and surface processes, generating a remarkable diversity of geochemical conditions. The mineral fingerprints preserved across these landscapes record long-lived groundwater activity and recurring wet-dry cycles, offering clues to how similar water-rock interactions may have shaped potentially habitable environments on the Red Planet.

The geochemistry of lake beds varied widely in response to these hydrologic fluctuations, the researchers found. In some shallow lakes, salt was the predominant mineral that accumulated. In others, a wider variety of minerals, including aluminum-rich clays and iron oxides, built up over time. Acidity and salinity levels also varied.

Some Australian lakes show depositions similar to craters in the Terra Sirenum region on Mars, suggesting that similar hydrologic processes might have taken place over the planet’s history. In some cases, the findings contradict long-held notions that magmatism must have shaped portions of Mars’s surface.

Even though these combinations of salts and acidic minerals indicate extreme lake conditions, the lakes in Western Australia still support diverse microbial life, suggesting that Terra Sirenum might be one of the best places to look for evidence of potential life on Mars, the authors wrote. (Earth and Space Science, https://doi.org/10.1029/2026EA005066, 2026)

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

Citation: Sidik, S. M. (2026), What Australian lakes showed us about Martian hydrology, Eos, 107, https://doi.org/10.1029/2026EO260244. Published on [DAY MONTH] 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
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body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news that impacts science and scientists today.

It’s well-documented that climate change is killing people.

A few months ago, the University of Chicago’s Climate Impact Lab released a report that found that, by 2050, about 10 times as many heat-related deaths would occur in poor countries as in richer ones.

Today, the same lab released a new report. This one found that the regions most affected by extreme heat are also the regions least likely to have increased levels of electricity to power the air conditioning that might provide relief. Use of cooling-related electricity is projected to grow seven times more in middle-income countries than in low-income countries in response to climate change.

“Air conditioning is a life saver, and climate change will no doubt lead to more AC adoption in today’s wealthy countries. Our research finds, however, that in too many countries around the world people will not be able to respond in the same way. The result is one of climate’s great cruelties—lots of death in the very countries that have contributed the least to climate change,” Michael Greenstone, a co-founder of the Climate Impact Lab, said in a statement.

 Related

•  Read the Report: Measuring the impact of rising temperatures on energy consumption to target adaptation planning
•  Major Investment in Air-Conditioning Needed to Address Future Heat Waves
•  Poor Countries Could Suffer 90% of all Heat-Related Deaths By 2050
 

The researchers describe “mortality cooling trap” areas, or locations where increased electricity consumption would most improve human welfare and save lives, but where such increases in consumption are not projected. The 18 identified countries are home to 676 million people, and about 377,000 people in these areas are projected to die each year beginning in 2050, thanks to the combination of hotter temperatures and low projected increases in energy consumption.

Most of the areas are in northern sub-Saharan Africa, in countries such as Burkina Faso, Chad, Mali, and Niger, with others in southern Asia, including Bangladesh, Myanmar, Nepal, and Pakistan.

This chart shows countries in the “mortality-cooling trap,” in decreasing order of the percentage of their population that live in mortality-cooling trap regions. Click to enlarge. Credit: Adaptation Roadmap: Energy, Climate Impact Lab, July 2026

The analysis accounted for deaths caused explicitly by heat, such as heat stroke, as well as related deaths, such as heat-related disease or cardiovascular stress, Genevieve Maricle, executive director of the Climate Impact Lab, said in an email to Eos.

Maricle told Eos that one of the most striking parts of the report to her was the differences in the death tolls between lower-income and higher-income countries, even when those countries have similar climates. For instance, Saudia Arabia faces high temperatures similar to those in Niger, but the projected increase in electricity use per person is approximately nine times higher in Saudia Arabia than Niger. The report found that by 2050, heat will claim 27,000 more lives per year in Niger than it will in Saudi Arabia.

“The disparity in projected deaths between regions is striking and lays bare how tightly climate resilience and energy are bound together,” Maricle wrote. “The communities facing the most extreme heat are also locked out of the cooling that could protect them – a deadly combination of maximum exposure and minimum defense.”

—Emily Gardner (@emfurd.bsky.social), Deputy Editor

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A significant reactivation occurred over the weekend of the 22 January 2026 Mauao landslide in Tauranga.

Loyal readers will remember my posts on the Mauao landslide in Mount Maunganui in New Zealand on 22 January 2026, which killed six people. Over the weekend, heavy rainfall caused the landslide to reactivate. Fortunately, in this case there have been no fatalities.

1News has a video of the immediate aftermath of the landslide, shot by a local resident. It includes this still of the immediate aftermath:-

The aftermath of the reactivation of the Mauao landslide in New Zealand. Still from a video posted by 1News.

Meanwhile, Charlie Rahiri from Tauranga City Council has posted this video explaining the situation:-

Tauranga City Council reports that there have been three landslides in recent days at the Mauao landslide site. The head scarp has retrogressed about 20 metres and 8,000 m3 of material has moved over a maximum distance of about 100 metres.

It was an interesting choice to film the video directly at the foot of the debris given that the slope is considered to be unstable and the mass is, in the words of the council, “saturated, mobile and fluid“.

The rear scarp of the landslide remains steep and quite tall, so further reactivations of the Mauao landslide cannot be precluded. This is strong evidence that the situation remains very challenging, but also that New Zealand is well versed in terms of managing these risks.

Taranga City Council has an excellent webpage dedicated to updates regarding the Mount Mauao landslide.

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Source: Journal of Geophysical Research: Planets

Io—Jupiter’s third-largest moon—is constantly kneaded and deformed by the gravitational pull of Jupiter and two of its other moons, Europa and Ganymede. The resulting friction inside Io generates extreme internal heat, fueling volcanoes that erupt all over its surface. In fact, Io is more volcanically active than any other world in our solar system.

Nearly all prior observations of Io’s heat have relied on infrared measurements that could detect temperatures only at the moon’s very outermost “skin.” Now, Brown et al. have taken Io’s internal temperature for the first time.

The researchers used data captured by the Microwave Radiometer instrument aboard NASA’s Juno spacecraft—which has orbited Jupiter since 2016—during close flybys of Io in December 2023 and February 2024.

These data revealed Io’s thermal emissions at microwave wavelengths, which are longer than infrared, enabling the researchers to peer beneath the surface for tens of meters. Their analysis involved identifying and removing portions of the data representing reflections of the sky on the moon’s surface. The goal was to be left with observations truly representative of Io’s characteristics.

These observations showed that the upper tens of meters of Io’s surface are strongly heated by internal processes. Two possible explanations that fit the data are that heat may rise steadily through a conductive layer near the surface and that heat from recent lava flows or hot vents may escape to the surface through thin patches of cooling crust, with the latter being more likely on the basis of the existence of tall mountains.

Further analysis of the microwave observations revealed more about Io. The data suggest that Io has a relatively smooth surface, similar to Earth’s plains. They also suggest that Io has an upper layer with a lower density than solid rock, perhaps similar to volcanic ash or pumice, which likely lies atop denser material several meters below.

These findings and further analysis of Juno’s Microwave Radiometer data could lead to a deeper understanding of Io, particularly the mechanisms by which it loses internal heat and how heat flow patterns may differ across its surface. This work could also help to inform the design of microwave-detecting instrumentation for future missions to Io or other rocky and icy worlds. (Journal of Geophysical Research: Planets, https://doi.org/10.1029/2025JE009622, 2026)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2026), Io’s hidden heat revealed for the first time, Eos, 107, https://doi.org/10.1029/2026EO260234. Published on 24 July 2026. Text © 2026. 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.

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In April, President Donald Trump officially revoked a ban on mining that had protected more than 225,000 acres (91,054 hectares) of federal land in Minnesota’s Superior National Forest from mineral exploration and development.

“It’s official. The illegal mining ban put in place by former President Biden has been overturned indefinitely, ending a reckless policy that sidelined Minnesota’s miners and undermined our nation’s ability to source our own materials,” Rep. Pete Stauber (R-Minn.) said in a statement after the repeal.

The action stoked new public concern about two proposed mines near the Boundary Waters Canoe Area Wilderness, a remote, million-acre part of Superior National Forest peppered with interconnected lakes and streams. The NewRange Copper Nickel company’s NorthMet mine, a joint venture of PolyMet Mining Corporation and Teck Resources, would be located approximately 20 miles (32 kilometers) from Boundary Waters in the St. Louis River watershed, which drains into Lake Superior. The Twin Metals Minnesota mine, owned by the multinational mining company Antofagasta PLC, would be located even closer to Boundary Waters and within the Rainy River watershed, which ultimately drains into Lake of the Woods, a lake shared by the Canadian provinces of Ontario and Manitoba as well as Minnesota.

Trump’s repeal of the mining ban is just the latest step in a yearslong battle over the future of mining in northeastern Minnesota, which is a magnet for recreationists and mining companies alike because of a geologic past that created pristine lakes atop rich deposits of critical minerals.

A Rift in the Bedrock

The deposits targeted by NewRange and Twin Metals were formed as a result of a rifting event that took place in the Proterozoic eon, roughly a billion years ago, during which the North American continent was expanding and breaking apart, said Adam Simon, a geologist at the University of Michigan who studies mineral deposit formation. “You can literally think of it as a crack or unzipping of the crust.”

The rift ran from the northeastern corner of Lake Superior, through what is now southwestern Minnesota, and into current-day Iowa and Kansas. The separation of the continent reduced pressure on Earth’s interior, which allowed molten rock to rise from the mantle to just below the surface, and some even erupted at the surface as lava flows. Molten rock from Earth’s mantle contains high concentrations of metal sulfide minerals of interest to mining companies today, including copper, gold, silver, platinum, cobalt, nickel, and chromium.

The rifting event that formed the Duluth Complex stretched across the Great Lakes Region and created intrusions of magma (colored in red) rich in valuable minerals. Credit: Wikimedia Commons/USGS, Public Domain

This uplift of magma, followed by hundreds of millions of years of erosion from glaciers, eventually formed what geologists now know as the Duluth Complex, a roughly 100-mile-long (161-kilometer-long) area north of Duluth, Minn., rich in metal sulfides.

Sulfate Streams

Today, Minnesota is the “Land of 10,000 Lakes,” and many residents worry about the potential impacts of mining in the water-dominated landscape.

The main concern is sulfate, a by-product of the separation of metals from the sulfide minerals that encompass them. Mining companies typically try to contain sulfate by storing mining waste in underground pits and chemically treating water that has been used in mining processes, though mining is still a significant source of sulfate in natural waters.

Though sulfate itself is not harmful to wetland ecosystems, it can cause a range of ecological issues once it is chemically transformed, said Amy Myrbo, a geologist and environmental consultant in Minneapolis. Naturally occurring bacteria in lake bed mud transform sulfate to sulfide, which creates hydrogen sulfide, a substance harmful to plants, when dissolved. In Minnesota, wild rice is an edible wetland grass that serves as an important food source and sacred plant to Indigenous groups; it reacts poorly to water high in sulfide. Additionally, the process can make water browner, fuel algal blooms, and increase freshwater concentrations of a harmful, bioaccumulative form of mercury.

“It’s a really underappreciated contaminant.”

Sulfate is “a really underappreciated contaminant” in fresh water, she said.

Though mines themselves are prohibited within the Boundary Waters area, environmental advocates are concerned that sulfate pollution from mine waste could flow in the wilderness’s waterways. The Boundary Waters wilderness is particularly susceptible to the nutrient-increasing effects of sulfate because its lakes tend to have a high amount of organic matter in their sediments, Myrbo said. “If we get sulfate pollution there, it could really be a problem.”

Minnesota is the only state with a sulfate water quality standard, meant to protect waters used for wild rice production. That standard is one of the only measures keeping the two proposed mines from moving forward, as dozens of wild rice waters are located within watersheds where the two proposed mines would be located.

Controlling Mine Waste

Open-pit mines are common in Minnesota, where iron deposits can be found at very shallow depths. The NewRange mine, though not an iron mine, would also be open-pit.

The Twin Metals project, however, would be an underground mine. Mining this way “significantly reduces the surface environmental impact,” Simon said. “What they’re essentially doing is surgically removing the ore underground.”

Still, separating metals from sulfide minerals creates mining waste high in sulfate, a slurry-like substance called mine tailings. Twin Metals plans to control this waste by drying it and compacting it into a mound that will then be “reclaimed with native soil and vegetation,” a method called dry stacking.

NewRange Copper Nickel plans to store its tailings in an existing facility provided by a closed iron mine. The company states that its methods will “clean up water quality issues from legacy iron ore mining and processing, leading to net reductions in loading of mercury and sulfate in the St. Louis River.”

“If someone says they’re going to open a sulfide ore mine without environmental contamination, they’re saying, ‘We’re going to be the first ones to ever do this.’”

Environmental advocates doubt that either company has an infallible plan to contain its waste because of the track record of similar mining projects. For example, one report commissioned by Northeastern Minnesotans for Wilderness in 2025 reviewed eight hard-rock mines in the United States and found that all eight had degraded downstream water quality. A 2012 report from the environmental advocacy group Earthworks that reviewed 14 copper mines (representing 89% of U.S. copper production according to the most recent data at the time) found that each of the mines had experienced at least one spill or accidental release of mine waste.

“If someone says they’re going to open a sulfide ore mine without environmental contamination, they’re saying, ‘We’re going to be the first ones to ever do this,’” said Steve Emerman, a geologist and environmental consultant. Emerman advises the Friends of the Boundary Waters, an advocacy group, on the effects of mining on the wilderness area.

NewRange Copper Nickel and Twin Metals did not respond to requests for comment.

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

Citation: van Deelen, G. (2026), One billion years ago, northern Minnesota nearly split apart. Now, two companies want to mine the aftermath., Eos, 107, https://doi.org/10.1029/2026EO260239. Published on 24 July 2026. 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.

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.

23 July: This article was updated to include comments from Jennifer Jones and Colette Delawalla.

A report released this week directs the U.S. government to spark a “new golden age” of science by ushering funds toward artificial intelligence, fostering closer relationships with private industry, and dismantling and rebuilding the federal science funding process.

The report was written by Michael Kratsios, director of the White House Office of Science and Technology Policy. He outlined his recommendations to Congress at a hearing of the House Committee on Science, Space, and Technology on 22 July. 

Kratsios intended the report to emulate a letter written to President Franklin D. Roosevelt by Vannevar Bush in 1945, called Science, the Endless Frontier, which set the foundation for the current U.S. federal science process in which federal funds support university research. “As we celebrate the United States’ 250th anniversary, we have the responsibility to renew our foundations once more,” he wrote.

Kratsios listed four goals to guide this approach to U.S. science: to “prioritize the individual scientist over legacy institutions,” to “fundamentally change how research dollars are allocated, distributed, and assessed,” to “set clear scientific goals and build the industrial muscle to translate scientific discovery into technological strength,” and to “prepare our research enterprise for the AI revolution.”

“If you think about this report in the context of everything else this administration has done, it really is about weakening independence, weakening accountability, [and removing] scientific integrity protections in favor of empowering political appointees,” said Jennifer Jones, director of the Center for Science and Democracy at the Union of Concerned Scientists.

Science-A-New-Golden-Age_EosDownload

The report recommends a handful of federal priorities to achieve these goals, including the Genesis Mission, a “national effort to harness AI for scientific discovery at a scale no other nation can match” led by the Department of Energy (DOE).

At the 22 July hearing, Kratsios said the Genesis Mission “is the crown jewel of American AI for science” and announced that federal agencies have committed more than $5 billion to the project. So far, 278 awards have been made, the largest being a three-year, $60 million grant for a project that will “help deliver nuclear facilities faster and safer” with the use of AI, according to the DOE. 

“There’s no mention of scientific integrity, no mention of protections for independence, it’s just the opposite.”

“There are some examples in STEM where AI is valuable,” such as increasing power in computational modeling or identifying new Earth-like planets at scale, for example, wrote Colette Delawalla, founder of science advocacy group Stand Up for Science, in an email. “But AI will never replace curiosity-driven scientific advancement,” she wrote. 

Some scientists viewed the report as a way for the government to justify steering research funds toward private industry and increasing political interference in science. “I think they’re trying to turn it into a venture capital model,” Jeremy M. Berg, a computational biologist and former director of the National Institute of General Medical Sciences at the National Institutes of Health, told The New York Times. 

“Under the hood,” the report is a “vision for faster technology development and commercialization while underinvesting in the fundamental research, expert peer review, and scientific workforce that make those advances possible,” Keivan Stassun, an astrophysicist and member of the National Science Board prior to its dissolution by the Trump administration, told Science.

What’s interesting about the report, Jones said, is what it doesn’t mention. “There’s no mention of scientific integrity, no mention of protections for independence, it’s just the opposite,” she said. “There are no clear systems of accountability” explained in the report, and its suggestion to funnel funds to individual researchers rather than institutions such as universities also means more research could occur outside of universities’ established and robust systems of accountability, she added.

The recommendations in the document largely align with recommendations made by former National Academy of Sciences president Marcia McNutt in June. In the annual president’s address, McNutt encouraged the scientific community to “better understand the needs of industry” and embrace the use of AI to increase research efficiency. 

At the hearing, however, Kratsios agreed with Rep. Brian Babin (R-TX), chair of the committee, that the National Academies of Science, Engineering, and Medicine required more federal oversight, especially in light of its recent report on climate attribution science that Babin said raised “transparency concerns.” Kratsios said he looked forward to working with Congress to codify the recommendations made in the “new golden age” report.

Funding the Golden Age

The vision the report presents is accompanied by recommendations from Kratsios and Russell Vought, director of the Office of Management and Budget, for the FY 2028 budget. These recommendations include prioritizing funding for physical sciences, including quantum physics, chemistry and materials sciences, mathematics and computer sciences, engineering, and biological sciences. 

For FY 2028, “agencies should align their R&D investments, where appropriate, with the Administration’s national missions,” the report states, listing those “national missions” as AI, quantum computing, fusion power, the construction of a lunar base and return of humans to the Moon, autonomous robotics, and semiconductor technology. 

 
Related

•  Read the Report: “Science: A New Golden Age”
•  Watch the Hearing: “Examining the Priorities of the FY2027 Research and Technology Enterprise”
•  Trump’s Plan for Science: More Money for A.I., Less for Universities
•  Trump Administration Steers $5B Toward AI Research
•  Get Involved: AGU Science Policy Action Center
 

At the 22 July hearing, Democrats argued that the Trump administration’s actions have worked against the stated goals of Kratsios’s report. “Big new initiatives and promises mean nothing when agencies act capriciously, canceling grants midway, delaying awards for months, even after they’ve been selected through the rigorous merit review process, and blacklisting educational and research institutions,” said Rep. Zoe Lofgren (D-CA).

The report did not mention the Trump administration’s proposed FY 2027 budget, which, if finalized, would reduce the National Science Foundation’s budget by 53%, the U.S. Geological Survey’s budget by 37%, the NASA science budget by 42%, and NOAA’s budget by 28%.

“I anticipate the report will be used as the rationale for making further cuts in the budgets and staffing of federal research agencies while limiting their authority and accountability to the American people,” Neal Lane, former director of the NSF, told Science. 

The report also did not mention recent sweeping cuts to the NSF’s FY 2026 budget, the fact that the NSF currently has no director, or a June proposal from the Office of Management and Budget that, if finalized, would give political appointees final approval power for scientific grants.

—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 © 2026. 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 winter earthquake of 923 or early 924 CE remains the benchmark event in the Seattle Fault Zone. It lifted shorelines around Puget Sound and gave geologists one of the most decisive records of the fault’s power.

But that shoreline-lifting earthquake is only part of the zone’s history. A recent Geological Society of America Bulletin study led by Stephen J. Angster, a geologist with the U.S. Geological Survey, looks past the most famous Seattle fault earthquake to examine evidence of earthquakes on lesser-known secondary faults.

At Lytle Beach on Bainbridge Island and at Vasa Park near Bellevue, subtle landforms and trench records suggest evidence of smaller ruptures has been preserved in the landscape but not fully recognized.

At Lytle Beach, the first clue was a small, raised surface. Angster described the “localized uplifted terrace” as “the first feature we saw that drew our eye to that area.” Similar features had already helped geologists read other secondary faults in the Seattle Fault Zone.

For instance, Angster said the Toe Jam Hill fault became one of the better-known examples when lidar helped reveal its scarp through dense vegetation. Later work found smaller uplifted terraces near similar secondary structures, which Angster said may indicate separate earthquake events focused on smaller faults rather than the larger regional rupture.

However, Lytle Beach stood out in a different way, as its fault dips south, in contrast to the zone’s better-known secondary faults, which dip north.

Faults Hidden in the Fold

Finding the localized uplifted terrace was only the beginning for Angster, who used lidar to uncover scarps and lineaments through the region’s forest cover.

His team also utilized ground-based magnetic transects across the Lytle Beach fault to look for changes that may reveal displacement beneath the surface. In addition, they gained a more direct view of disturbed sediments by excavating the Rose Hip trench across the newly identified Lytle Beach scarp and analyzing evidence from the earlier Vasa Park trench.

In the Rose Hip trench at Lytle Beach, Angster said the team found glacial deposits dating to roughly 15,000 years ago. Above them were lake sediments left behind as ice retreated. The trench also preserved an old layer of soil that formed after the lake dried. “That whole package was folded,” he said. “The only way you could fold those is mostly by a tectonic fault.”

A regional map of the Seattle Fault Zone shows the Lytle Beach and Vasa Park fault scarps, along with the uplifted shore platform associated with the 923 CE earthquake. A new study used mapping, geophysics, trenching, and dating methods to investigate secondary faults within the broader fault zone. Credit: Angster et al., 2026, https://doi.org/10.1130/B38333.1, CC-BY-4.0

The trench record showed evidence of two surface-rupturing earthquakes on the Lytle Beach fault. The older event occurred between 11,240 and 10,430 calibrated years before present, whereas the younger event occurred after 1663 CE, likely in the early nineteenth century. (“Calibrated years before present” refers to dates arrived at via radiocarbon dating, relative to the year 1950 as the “present.”)

“I thought the trenching on Lytle Beach was surprising, that we found two events, because it was such a relatively subtle feature that wasn’t really identified before,” Angster said.

At Vasa Park, the team found evidence of one past earthquake that occurred sometime between 11,380 and 7,400 calibrated years before present. That range overlaps with the older Lytle Beach event and raises the possibility of a longer rupture along the Blakely Harbor fault. However, the evidence in Angster’s study better supports separate ruptures on the two secondary faults.

A Longer Record of Smaller Ruptures

Harold Tobin, an earthquake scientist at the University of Washington who was not involved in the study, called the work “exciting new research.”

He said the study shows there is “room to accommodate smaller earthquakes” that do not reshape shorelines like the 923 or 924 event but are “still big enough to be damaging earthquakes.” The Angster paper, he said, examines “additional earthquakes not accounted for in the shoreline uplift record centered on the 923 or 924 event. These smaller earthquakes may have happened more recently or more often.”

“Subtle features, relatively small or fault traces that we might have ignored before, can be an important part of the story.”

For Tobin, the value also extends beyond Puget Sound. The study “shines a light for other people working in cities and urbanized settings,” he said, because it shows that “subtle features, relatively small or fault traces that we might have ignored before, can be an important part of the story.”

By comparing the dated events at Lytle Beach, Vasa Park, and other secondary faults, the authors estimated that these faults may have ruptured roughly every few hundred years during the late Holocene. Angster cautioned that it’s not quite clockwork. “The secondary faults appear, especially within the last 2,500 years, to rupture more frequently, and that’s where that 350-year interval comes from,” he said. But the estimate rests on a limited record.

Though the work doesn’t forecast the next earthquake, it gives scientists more of the past to weigh as they assess the Puget Lowland. Tobin said the paper “certainly beg[s] more research” because the Seattle Fault Zone contains many strands that still need to be studied. Earthquake hazards should remain “something real” for the public and civil planners.

“We don’t know when they are going to come,” Tobin said. “Obviously, we can go decades without any significant earthquakes, as we have since 2001. But when we least expect it, one will happen, and we just have to be prepared.”

Angster framed the findings more conservatively: “This study doesn’t really change the hazard with the Seattle Fault. It just provides more insight into how it behaves.”

—Jason Collins, Science Writer

Citation: Collins, J. (2026), Small faults add to Seattle’s quake story, Eos, 107, https://doi.org/10.1029/2026EO260238. Published on 23 July 2026. Text © 2026. 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 that impacts science and scientists today.

What exactly is a moon? It’s an existential question lunar researchers found themselves pondering when they discovered an exosatellite at least 90% the size of Jupiter, orbiting a brown dwarf in a system about 73 light-years away from Earth.

 
Related

•  Read the Paper: Satellite Discovered Around a Star’s Substellar Companion
•  What Makes a Moon?
•  Very Large Telescope
 

Depending on how exactly one defines “moon,” the object could be the first moon definitively discovered outside our solar system.

If a moon is a body orbiting another body that is orbiting a star, then yes, we’ve got a moon on our hands. But this exosatellite is orbiting a brown dwarf, a body far larger than most planets but too small to sustain hydrogen fusion as stars do, instead of a planet. And it’s enormous in a way our local moons aren’t.

The whole system is really weird, explained lead author Kevin Hoy in an email to Eos. Hoy is a European Southern Observatory astrophysics Ph.D. student who is also affiliated with the Instituto de Estudios Astrofísicos at the Universidad Diego Portales in Chile and its Millennium Nucleus of Young Exoplanets and their Moons research center.

“The host star is much smaller than the Sun, the brown dwarf is much heavier than our most massive planet, and the satellite is much heavier than any of the moons in our system,” Hoy said. “No part of this system has an obvious comparison to any object in the Solar System.”

The researchers published their findings today in Nature.

When Words Fail

The scientists detected the maybe-moon in the CD-35 2722 system using the radial velocity method, which is often used to detect exoplanets. The brown dwarf moves slightly in response to the exosatellite’s orbit, as the exosatellite exerts a slight gravitational pull. These movements can be seen from Earth as small changes in the brown dwarf’s light spectrum. Scientists observed 26 of these changes from the European Southern Observatory’s Very Large Telescope (VLT) in Chile between October 2023 and February 2026.

The scientists ran several models to see what could explain the periodic changes, including a model in which the brown dwarf actually had two exosatellites. The best explanation to fit the data, they found, was one satellite at least 90% as massive as Jupiter orbiting the brown dwarf approximately every 170 days. (The brown dwarf itself is about 37 times as massive as Jupiter, meaning that although the proposed exomoon is huge, it could be proportionally much less massive compared to its primary than the Moon is to Earth.)

The combination of techniques the researchers used were first proposed for detecting exomoons in 2018, in a paper coauthored by Andrew Vanderburg, now an astronomer at Harvard University.

“I never would have imagined that this technique would reveal such an unusual object!” Vandenburg said in an email to Eos. He added that he wondered what exactly the exosatellite was, how it formed, and how big it was. “Regardless, it’s an amazing discovery and I’m super excited to see what else we can find by observing planets like this!”

Researchers have discovered more than 6,200 confirmed exoplanets so far, but only a few candidates for exomoons have been detected, and none have been confirmed. Such a discovery could help us learn more about how various parts of the universe were formed, and how they function today, the paper suggests.

Though it’s possible some unknown variable in the brown dwarf itself could be responsible for the periodic changes in radial velocity the team observed, “we can’t think of any physical mechanism that could reproduce the signal we see,” said Hoy, the lead author of the study. “That’s why we think a satellite is the most likely explanation.”

In this case, the scientists are confident about what they’ve found. They’re just not sure exactly what to call it.

“Perhaps we are approaching the limit of language invented to describe the Solar System, which is entirely unlike CD-35 2722,” the paper reads.

—Emily Gardner, Deputy Editor (@emfurd.bsky.social)

These updates are made possible through information from the scientific community. Do you have a story about science or scientists? Send us a tip at eos@agu.org. Text © 2026. AGU. CC BY-NC-ND 3.0
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