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At UC Berkeley's Central Sierra Snow Laboratory, located at 6,894 feet above sea level near Donner Pass, researchers collect detailed measurements of the snowpack each day. There is still some snow on the ground to measure, but less than they usually see in late January.

It’s not easy to determine how much water there is across a landscape. A measly 1% of Earth’s freshwater is on the surface, where it can be seen and measured with relative ease. But beneath that, measurements vary massively depending on water table depth and ground porosity we can’t directly see.

“We’re operating in a situation where we don’t know how much is going into the savings account every month, and we don’t know how much is in our savings account.”

Reed Maxwell, a hydrologist at Princeton University, likes to think of rainfall, snow, and surface water as a checking account used for short-term water management needs and groundwater as a savings account, where a larger sum should, ideally, be building up over time.

“We’re operating in a situation where we don’t know how much is going into the savings account every month, and we don’t know how much is in our savings account,” he said.

But a new groundwater map by Maxwell and colleagues offers the highest-resolution estimate so far of the amount of groundwater in the contiguous United States: about 306,500 cubic kilometers. That’s 13 times the volume of all the Great Lakes combined, almost 7 times the amount of water discharged by all rivers on Earth in a year. This estimate, made at 30-meter resolution, includes all groundwater to a depth of 392 meters, the deepest for which reliable porosity data exist. Previous estimates using similar constraints have ranged from 159,000 to 570,000 cubic kilometers.

“It’s definitely a move forward from some of the previous [mapping] efforts,” said Grant Ferguson, a hydrogeologist at the University of Saskatchewan who was not involved in the research. “They’re looking at much better resolution than we have in the past and using some interesting techniques.”

Well, Well, Well

Past estimations of groundwater quantity have been based largely on well observations.

“That’s the really crazy thing about groundwater in general,” said Laura Condon, a hydrologist at the University of Arizona and a coauthor of the paper. “We have these pinpricks into the subsurface where there’s a well, they take a measurement of how deep down the water table depth is, and that’s what we have to work with.”

But not all wells are measured regularly. For obvious reasons, there tend to be more wells in places where more groundwater is present, making data on areas with less groundwater scarcer. And a well represents just one point, whereas water table depth can vary greatly over short distances.

Researchers have used these data points, as well as knowledge of the physics of how water flows underground, to model water table depth at a resolution of about 1 kilometer. They’ve also used satellite data to capture large-scale trends in water movement. But those data are of lower resolution: Data from NASA’s GRACE (Gravity Recovery and Climate Experiment) Tellus mission, for instance, have a resolution of about 300 kilometers, about 10,000 times coarser than the new map.

To demonstrate the value of high-resolution data, the team showed what happened when they decreased the resolution of their entire map from 30 meters to 100 kilometers—the spatial resolution of many global hydrologic models. The resulting more pixelated map estimated just above 252,000 cubic kilometers of water, an underestimation of 18% compared to the new map.

In addition to identifying groundwater quantities at high resolution, the new map reveals more nuanced information about known groundwater sources.

For instance, it shows that about 40% of the land in the contiguous United States has a water table depth shallower than 10 meters. “That 10-meter range is that range where you can have groundwater–plant–land surface interactions,” Condon said. “And so that’s just really pointing to how connected those systems are.”

Bias for Good

The new work used direct well measurements as well as satellite data—about a million measurements, made between 1895 and 2023—along with maps of precipitation, temperature, hydraulic conductivity, soil texture, elevation, and distance of streams. Then, the scientists used the data to train a machine learning model.

In addition to its being able to quickly sort through so many data points, Maxwell noted another benefit of the machine learning approach that might sound unexpected: its bias. Early groundwater estimates were relatively simplistic, not accounting for either hydrogeology or the fact that humans themselves pump water out of the ground. The team’s machine learning approach was able to incorporate that information because evidence of groundwater pumping was present in the data used to train it.

“When you hear about bias in machine learning all the time, it’s usually in a negative connotation, right?” Maxwell said. “As it turns out, when you can’t disentangle the signal of groundwater pumping and groundwater depletion from the almost 1 million observations that we used to train this machine learning approach, it implicitly learned that bias.… It’s learned the pumping signals, it’s learned the human depletion signal.”

“Wherever you’re standing, dig down, and there’s water down there somewhere.”

Maxwell and the other researchers hope the map can be a resource for regional water management decisionmakers, as well as for farmers making decisions about irrigation. Condon added that she hopes it raises awareness of groundwater in general.

“Groundwater is literally everywhere all the time,” she said. The map is “filled in everywhere, wherever you are. Some places it’s 300 meters deep, some places it’s 1 meter deep. But wherever you’re standing, dig down, and there’s water down there somewhere.”

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

Citation: Gardner, E. (2026), Report: 13 Great Lakes’ worth of water underlies the contiguous United States, Eos, 107, https://doi.org/10.1029/2026EO260036. Published on 26 January 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.

An experiment in western China over the past four decades shows that it is possible to tame the expansion of desert lands with greenery, and, in the process, pull excess carbon dioxide out of the sky.

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

A crucial source of freshwater, groundwater is vulnerable to contamination and overuse. Knowing how long groundwater has been under ground is critical for sustainable management of this resource. The Carbon-14 (14C) and Argon-39 (39Ar) isotopes are environmental tracers especially suited for dating groundwater aged between 50 and 30,000 years. However, ages obtained from previous analyses of these two tracers disagreed with each other.

Musy et al. [2025] use a quantitative framework to understand the effect of groundwater flow within the Earth’s subsurface on the age calculated from 14C and 39Ar measured in aquifers in Denmark. Reactions that affect 14C, the production of 39Ar in the subsurface, and the existence of slow and fast paths for groundwater flow, such as in fractured aquifers, explain the differences observed between age estimates. Accounting for these processes leads to more accurate estimate of groundwater residence times and supports better water resource management.

Citation: Musy, S. L., Hinsby, K., Wachs, D., Sültenfuss, J., Troldborg, L., Aeschbach, W., et al. (2025). Bridging the 39Ar–14C groundwater dating gap: A dual-permeability transport perspective based on numerical modeling and field data. Water Resources Research, 61, e2025WR040370. https://doi.org/10.1029/2025WR040370

—Sergi Molins, Associate Editor, Water Resources Research

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.

Stronger El Niño events are more likely when springtime surface waters in the western Pacific Ocean become unusually salty, a new study in Geophysical Research Letters suggests. Traditionally, scientists have focused on temperature and wind patterns to understand El Niño—periodic shifts in the tropical Pacific between warmer and cooler conditions that influence weather patterns across the globe. But researchers now show that subtle variations in ocean salinity north of the equator during boreal spring (March to May) can substantially amplify El Niño's strength and nearly double the odds of an extreme event.

This month, AFP reported from OceanXplorer, a high-tech marine research vessel owned by billionaire-backed nonprofit OceanX, as it studied seamounts off Indonesia.

A dome-fronted submersible sinks beneath the waves off Indonesia, heading down nearly 1,000 meters in search of new species, plastic-eating microbes and compounds that could one day make medicines.

A new study of climate extremes since 1988 finds that many regions have seen increases in deaths due to floods, storms and extreme temperatures. In human terms, the harm comes not just from deaths, but also from lost labor and property damage. (And this doesn't consider damage to species and ecosystems.) A new look at trends and outliers has been published in Geophysical Research Letters.

Publication date: Available online 21 January 2026

Source: Advances in Space Research

Author(s): Kshitiz Upadhyay, Duggirala Pallamraju, Kavutarapu Venkatesh

Publication date: Available online 21 January 2026

Source: Advances in Space Research

Author(s): Fabienne Seibert, Jan Thimo Grundmann, Matteo Ceriotti, Bernd Dachwald

The atmosphere is an important transport medium that carries microplastics to even the most remote parts of the world. These microplastics can be inhaled and pose a health risk to humans and animals. They can also settle out of the atmosphere and contaminate oceans and soils worldwide.

Ancient pine trees growing in the Iberian mountains of eastern Spain have quietly recorded more than five centuries of Mediterranean weather. Now, by reading the annual growth rings preserved in their wood, scientists have uncovered a striking message: today's storms and droughts are becoming more intense and more frequent than almost anything the region has experienced since the early 1500s.

Predicting the duration of a Central Pacific El Niño event has long frustrated climate scientists and forecasters. Now, a new study reveals that Central Pacific El Niños follow two fundamentally different life cycles—and the difference is determined months before they peak.

SummaryFull waveform inversion (FWI) updates the velocity model by minimizing the discrepancy between observed and simulated data. However, incomplete seismic acquisition can introduce errors that propagate through the adjoint operator, affecting the accuracy of the velocity gradient and reducing the convergence accuracy and speed. To mitigate the influence of acquisition-related noise on the gradient, we employ a convolutional neural network (CNN) to extend the velocity representation and refine the velocity model before forward simulation, thus reducing gradient noise and providing a more accurate velocity update direction. The same data misfit loss is used to update both the velocity and the network parameters, forming a self-supervised learning procedure. Here, the CNN acts as a dynamic velocity conditioner that is optimized to help fit the data. In this method, the velocity representation is extended (VRE) by combining a neural network with conventional grid-based velocities. Thus, we refer to this general approach as VRE-FWI. Synthetic and real data tests demonstrate that the proposed VRE-FWI achieves higher velocity inversion accuracy compared to traditional FWI, with only a marginal additional computational cost ∼1%.

AbstractAnisotropy of magnetic susceptibility (AMS) analysis is widely used as an efficient petro-fabric tool to infer magma flow patterns within dikes. However, interpretations of magnetic fabric often get complicated by the occurrence of anomalous (intermediate/inverse) fabrics oriented normal to the dike plane, which may lead to uncertainty, unlike the straightforward normal fabrics along the intrusion plane. In this article, we present a detailed rock-magnetic and magnetic fabric study of India’s ~116 Ma old Salma dike, which is the most prominent and longest dike related to the early Cretaceous Rajmahal Trap (RT) volcanism. A joint analysis of in-phase and out-of-phase anisotropy of magnetic susceptibility (i.e. ipAMS and opAMS) and anhysteretic remanent magnetization (AARM) fabrics allowed us to identify the different sources of the observed fabric and subfabrics. Rock-magnetic analyses suggest that the magnetic mineralogy consists of at least two types of titanomagnetite with varying Ti-content. FORC suggests that the dike is dominated by PSD grains with varying influence from SD grains. The ipAMS fabric is primarily carried by SD grains of low-Ti titanomagnetite, while opAMS is governed by larger MD/PSD titanomagnetite with higher-Ti content. Results indicate that anomalous, intermediate-type ipAMS fabrics, particularly along the dike margins, are caused as a combined effect of SD grains, late-stage crystallization, and mild high-temperature oxidation. At the dike center, post-emplacement alteration, intense exsolution of the primary titanomagnetite, and magma backflow are responsible for anomalous fabrics. In contrast, the majority of normal ipAMS, opAMS, and AARM fabrics are coaxial, providing a reliable record of magma flow as confirmed from the long axes trend distribution of the plagioclase laths along the dike plane. These fabrics reveal a dominant subvertical magma flow direction during emplacement, indicating magma ascent from depth. Even though the magnetic fabrics do not unequivocally constrain the deeper processes underneath Moho, they are compatible with the idea of a subcrustal magmatic layer beneath the region, potentially originating from decompression melting or the influence of the Kerguelen plume, to be the feeder source.

CO2 that has been absorbed and accumulated in fresh water areas like lakes and reservoirs—is receiving attention for its potential contributions to achieving a carbon neutral society. Kobe University is a hub for freshwater carbon research, with Graduate School of Engineering Professor Nakayama Keisuke, an expert in aquatic and environmental engineering, at the forefront.

As temperatures rise and water supplies drop, public policy could bolster municipal water provisions under pressure. But one policy prescription—pushing conservation—will likely be insufficient as a standalone fix to sustain some reservoirs, according to research led by scientists at Penn State.

It's no secret that Florida's iconic coral reefs are in trouble. Repeated body blows from hurricanes, pollution, disease, climate change—and a near-knockout punch from a 2023 marine heat wave—has effectively wiped several species off the map and shrunk the reefs that stretch from the Keys throughout South Florida.

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

Understanding how deep continental rocks can be subducted into the Earth’s mantle is essential to understand lithospheric recycling, reconstructing deep subduction and exhumation processes. Minerals formed at great depths often preserve microscopic “exsolution” features, where one mineral separates out from another during cooling or decompression, but their interpretation has remained debated.

Li et al. [2025] performed the first systematic laboratory experiments on kyanite exsolution from aluminiferous stishovite, a high-pressure polymorph of SiO2 (silicon dioxide) stable at depths exceeding 300 kilometers. The experiments show that aluminum almost completely separates from stishovite to form kyanite during decompression, producing distinctive microscopic textures. These findings address a long-standing debate about whether a specific crystallographic relationship between exsolved phases and their host mineral is required to identify exsolution microstructures.

Importantly, the study demonstrates that a strict crystallographic alignment between the host mineral and exsolved phases is helpful but not always required to identify true exsolution. These results provide a robust experimental framework for interpreting similar microstructures observed in natural rocks. Overall, the findings offer compelling new evidence that continental rocks can undergo ultra-deep subduction into the mantle depths of at least about 300 kilometers and later be exhumed back to the Earth’s surface.

Citation: Li, X., Wang, C., Liu, L., Kang, L., Xu, H. J., Zhang, J., et al. (2025). Kyanite exsolution from aluminiferous stishovite in laboratory experiments: New insights into continental ultra-deep subduction. Journal of Geophysical Research: Solid Earth, 130, e2025JB031612. https://doi.org/10.1029/2025JB031612

—Jun Tsuchiya, Editor; and Sujoy Ghosh, Associate Editor, JGR: Solid Earth

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.

In August 2023, 18 scientists and engineers spent 15 days in barren regions of Iceland to test how well instruments on the VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) spacecraft will perform when investigating the surface of Venus from orbit. This testing was a critical step in developing procedures to enhance the science output of the mission, which will provide the first new data about the planet’s surface in more than 3 decades.

Iceland might not seem an obvious choice as an analogue for Venus.

Among other tasks, the team—including us—traversed rugged Icelandic terrain to sample lava flows for analysis on-site and, later, in the lab. We also used on-the-ground observations of the flows to calibrate and verify corresponding airborne-detected radar signatures, information that will be used to help interpret the radar data they collect on the Venus mission.

At first glance, Iceland might not seem an obvious choice as an analogue for Venus. After all, Iceland is cool, wet, and near the Arctic Circle. Venus is famous for its extremely hot and dry surface, where average temperatures are roughly 870°F (465°C). Yet the two share key commonalities as well.

Iceland is covered in basalt, the same rock that’s thought to make up the low-lying plains on Venus. Also, Iceland is underlain by an active mantle plume that feeds its volcanic vents, and Venus too shows evidence of having mantle plumes below its surface. With these similarities, scientists can make direct comparisons between the diverse morphologies, compositions, and signatures of Icelandic lava flows and those of flows on Venus. Such comparisons are needed to ensure that we can accurately interpret the data VERITAS sends back to answer long-standing questions about our most Earth-like neighbor.

Reading the Radar Signals

Magellan, the last mission to observe Venus’s surface, ended more than 31 years ago after spending 4 years in orbit. Data from Magellan offered unprecedented glimpses of the planet and opened new lines of inquiry for scientists. However, these data are relatively low resolution by today’s standards, complicating efforts to resolve surface features and understand how they relate to Venus’s geologic past.

In June 2021, NASA selected the Discovery-class VERITAS mission as a long-awaited follow-up to Magellan because its suite of instruments have the potential to reveal the processes that caused the evolution of Venus and Earth to diverge. While Venus likely once had surface water and a planetary dynamo, these essential elements of habitability are long gone. However, tectonism and volcanism, driven by robust internal heat production with associated outgassing, probably persist today, as suggested by evidence in a recent study. If Venus has active volcanism and tectonism, then VERITAS should be able to confirm that identification and to detect surface activity that has occurred since Magellan’s visit, such as new volcanic flows and fault scarps.

The VERITAS payload includes a synthetic aperture radar (SAR) platform to view the planet’s surface and to make topographic measurements using a technique called single-pass radar interferometry. Venus’s thick atmosphere precludes the use of visible light imaging for these purposes, leaving SAR as the only current way to observe its surface over wide areas at high resolution.

Like other radar systems, space-based SAR works by transmitting radio waves to a planet and then detecting signals reflected back to a receiver, which gives information about the surface. Radar data are fundamentally different from visible imagery, as the brightness of radar returns depends not only on surface material properties such as albedo and color, but also on surface roughness and electrical permittivity, and on other effects such as the polarization of radar signals and their penetration into a planet’s surface.

Topography is a key metric for unlocking the geologic processes that have shaped the evolutionary history of a planet.

This complexity makes it difficult to determine the geological properties of structures on Venus’s surface directly from their radar signatures. It is impossible to tell from orbital data alone whether any particular radar signature is caused by a rock’s roughness or its composition, because we do not have samples of Venus to test.

Topography is a key metric for unlocking the geologic processes that have shaped the evolutionary history of a planet. Existing topographic data from Venus were obtained by radar altimetry during Magellan at a spatial resolution of 15–20 kilometers and a vertical accuracy of 80–100 meters, each over an order of magnitude coarser than what’s available for other terrestrial bodies.

VERITAS will measure topography using single-pass radar interferometry with a spatial resolution of 240 meters and a vertical accuracy of 5 meters, which is in line with data from the Moon, Mars, and Mercury. This sharper view will dramatically improve scientists’ ability to compare Venus with these bodies and help decipher why it evolved so differently from Earth.

In addition to its radar capabilities, VERITAS’s Venus Emissivity Mapper (VEM) spectrometer will provide the first global-scale view of surface rock types, allowing discrimination of felsic from mafic rocks based on their iron content. These data will help scientists answer key questions about Venus’s history of volcanism and how it shaped the planet’s young surface, as well as about whether large plateaus called tesserae have a similar composition and origin as Earth’s continents (and whether they formed in the presence of water).

What Are Venus’s Rocks Made Of?

Geologic maps of Earth represent the composition and age of rocks in defining geologic units. On Venus, geologic units have been defined based on radar imagery alone, so scientists have had to make assumptions about the composition and formation of features by comparing their morphologies to those of well-known terrestrial features. However, without accurate knowledge of what the Venus rocks are made of, it is difficult to confirm hypotheses of the planet’s geologic history.

• The VERITAS field campaign explored remote regions of Iceland and encountered rugged conditions. Specialized off-road vehicles were required to access the field areas studied. Credit: Gaetano Di Achille
• Team members sometimes had to drive through running streams, as seen here on the drive from Mývatn to Askja. Credit: Debra Buczkowski
• The field team cooked, ate, slept, socialized, and analyzed data at campsites comprising two large tents surrounded by smaller personal tents for sleeping. Credit: Debra Buczkowski
• Terrain in several areas, including here at Askja, was extremely rough, which made for difficult hiking. Credit: Debra Buczkowski

Unlike with Mars or the Moon, ground truth of Venus orbital data is severely limited. The thick atmosphere obstructs remote sensing of rock composition from orbit. And past landers have not survived long enough on the surface to perform extensive testing, primarily because of the extremely hostile temperatures and atmospheric pressure (90 times that of Earth’s) at the surface. The VERITAS field campaign was therefore intended as a reality check, to test our geologic interpretations of radar observations.

Iceland’s extensive lava fields host a variety of volcanic and tectonic features similar to those observed on Venus.

The first goal of the campaign was to improve our ability to process, analyze, and interpret VERITAS-like data for the purpose of understanding Venus’s geology. The expedition in Iceland was an opportunity to create a library of radar signatures associated with specific surface features in volcanic landscapes, with direct measurements of both roughness and composition. The second goal was to test the methodologies and the approach that VERITAS will use to detect surface changes when it arrives at Venus.

Iceland’s extensive lava fields host a variety of volcanic and tectonic features similar to those observed on Venus, making them excellent choices as Venus analogues. The comparative lack of both vegetation and erosion at these sites makes them more comparable to those on Venus than basaltic lava fields elsewhere on Earth. In addition, the relative ages of different Icelandic lava flows are known and well documented, which allows us to determine whether radar data can be reliably used to tease out the ages of flows on Venus.

Three Sites, Three Environments

We focused the field campaign on three main basaltic lava flow fields: Askja, Holuhraun, and Fagradalsfjall. The diversity of geologic landforms within these sites enabled study of a range of features analogous to those that VERITAS will target on Venus. These features include plains volcanism, lobate flows, lava morphologies such as pāhoehoe and a’a, compositions ranging from basaltic to rhyolitic, pyroclastic airfall and wind-driven sedimentary deposits covering volcanic bedrock, tectonic rifts, and small-scale graben. The study areas also allowed us to investigate landforms created by interactions between sediment, tectonic structures, and lava flows and how these features appear in SAR data collected from orbit at different signal frequencies and incidence angles.

• The lava fields studied during the field campaign included Askja and Holuhraun, in Iceland’s central highlands, and Fagradalsfjall, on the Reykjanes Peninsula in the country’s southwest (top left). White lines within the red boxes represent the flight lines flown by the German Aerospace Center (DLR) to collect synthetic aperture radar (SAR) data. Credit: Dan Nunes (map imagery and data: Google, IBCAO, Landsat, Copernicus, SIO, NOAA, U.S. Navy, NGA, GEBCO)
• A tripod-mounted lidar instrument was used to take topographic measurements at all field sites, including here at Holuhraun. Credit: Sue Smrekar
• Researchers collect lidar measurements at the Fagradalsfjall field site. Credit: Dan Nunes
• Field campaign team members work with lidar instrumentation at the Askja site. Orange flags served as tie points for georeferencing the lidar images to airborne radar data. Credit: Debra Buczkowski

The Askja lava field, located in Iceland’s central highlands, is sourced from a central volcano and includes multiple areas with differing textures due to variations in the extent of sedimentation and erosion. Some Askja flows are covered with rhyolitic tephra and basaltic sand, offering additional textural and compositional diversity for study. Volcanism has occurred in the area for thousands of years, with the youngest flow (Vikrahraun) erupting in 1961.

Although geographically close to Askja, the Holuhraun lava field is sourced from a different magmatic reservoir and erupted from fissures. Sand sheets interact with the edges of the Holuhraun flows, especially along their northern boundary. The field also includes an extremely rough flow that was emplaced only about 10 years ago (2014–2015).

Located in southwestern Iceland on the Reykjanes Peninsula, the flows at Fagradalsfjall are even more recent, erupting from fissures starting in 2021 and continuing through 2025. (In fact, Fagradalsfjall was actively erupting at the beginning of the field campaign.) These recent flows, including pāhoehoe flows, are significantly smoother than those at Holuhraun and, because of their young age, have relatively little sediment coverage. Lava ponds and channels are also common here.

Air and Ground Campaigns The F-SAR sensor was installed on DLR’s Dornier 228 aircraft and flown out of Keflavik International Airport (left). The radar antenna mount is on the side of the fuselage just aft of the rear wheels. One of three trihedral radar reflectors deployed for use as reference targets during the campaign is seen at right. Credit: Marc Jaeger

The field campaign comprised both airborne and ground components. The German Aerospace Center (DLR), one of several agencies partnering with NASA on VERITAS, ran the airborne component, flying their F-SAR sensor aboard a twin-propeller plane to collect SAR data at three wavelengths (X-, S-, and L-band) at the same time the ground campaign team members visited each site.

The extensive multifrequency SAR dataset that DLR acquired covers the diverse geological features of the three lava fields and includes imagery that represents the differing spatial and vertical resolution capabilities of the Magellan and VERITAS missions, as well as those of the upcoming European Space Agency EnVision mission to Venus. Figure 1 shows an example of derived F-SAR topographic data for a lava flow at Holuhraun at simulated Magellan and VERITAS resolutions. Whereas the Magellan-like data only allow determination of the general slope of the landscape over a spatial scale of tens of kilometers, the VERITAS-like data enable spatial and vertical discrimination of distinct geologic units.

Fig. 1. A radar backscatter image above the Askja and Holuhraun lava fields (left) is seen here beside digital elevation models (DEM) produced with SAR topographic data at resolutions simulating those of Magellan radar altimeter data (center) and VERITAS radar altimeter data (right). White arrows point to the Holuhraun flow boundaries in all three images. Whereas at Magellan resolution, only a general regional slope can be discerned, at VERITAS resolution, it’s possible to pick out individual lava flows as well as Vaðalda Mountain. Credit: Scott Hensley

F-SAR operations also included deploying radar reflectors that were used as reference targets and regularly imaged to monitor sensor calibration and instrument stability throughout the campaign. In addition, a subset of the raw SAR data acquired was processed on-site within hours of each flight, providing imagery to inform the field teams’ site selection and prioritization within each lava field.

Team members braved river crossings and trekked across often-jagged rocks to take samples and collect information on the surface roughness and composition of the rocks being scanned from the air.

Concurrent with the radar data collection, VERITAS team members braved river crossings and trekked across often-jagged rocks to take samples and collect information on the surface roughness and composition of the rocks being scanned from the air. We simultaneously used lidar scanners to take topographic measurements at all field sites to compare with radar detections and a probe to determine electrical permittivity in sedimented areas. These measurements allowed us to determine how much of the radar backscatter signature at each site was due to the permittivity, rather than to roughness.

In addition, we used a field prototype of VERITAS’s VEM instrument, called the Vemulator, on-site to identify different rock types and compositions. Rock and sediment samples from all field sites were later tested in the lab to confirm field measurements of composition and permittivity, including those from the Vemulator.

Details Come into Focus

Following the field campaign, team members produced maps of the lava flows at all three sites based solely on the radar data, exactly as Venus researchers have made geologic maps of Venus using Magellan data. The new maps were made at three different resolutions: the resolution of the old Magellan data, the resolution of the VERITAS SAR, and the highest resolution available with the data collected during the campaign.

The improvement in SAR resolution from Magellan to VERITAS will permit observations of previously unidentified features on Venus (Figures 2 and 3). Views of the Holuhraun flow at Magellan resolution, for example, are too coarse to discern distinct lava flow units, or facies, whereas at the VERITAS resolution, separate facies, a small vent, and several lava ponds can be distinguished. Being able to identify similar features on Venus will allow us to detect changes on the surface since Magellan’s visit that would indicate recent volcanism, helping to better understand the planet’s volcanic history.

Fig. 2. SAR imagery of the Holuhraun flow is seen here at Magellan’s lower resolution and VERITAS’s higher resolution. In the latter case, lava ponds and a volcanic vent are observed (white arrows). Black boxes indicate the southwestern part of the flow that’s magnified in Figure 3. Credit: Debra Buczkowski Fig. 3. Even when magnified, no features within the Holuhraun flow can be discerned at Magellan resolution, whereas at VERITAS resolution, the volcanic vent (white arrow) and distinct flows coming from it are visible, as are other flow facies. Credit: Debra Buczkowski

Comparing our new aerial-radar-derived maps of the Iceland field sites with published maps based on ground observations enabled us to assess how well our flow boundaries matched what’s seen from the ground. In addition, we were able to determine how similar the observed radar properties were to actual flow composition and roughness. Once the flow boundaries were defined in the SAR datasets, we could also determine how overlying sediment influenced the radar appearances of different lava flows. This information could provide insight into how ashfalls or pyroclastic materials on Venus might obscure or alter the radar signature of underlying rocks.

When it arrives at its destination, VERITAS will create foundational datasets of high-resolution imaging, topography, and spectroscopy of Venus.

When it arrives at its destination, VERITAS will create foundational datasets of high-resolution imaging, topography, and spectroscopy of Venus. These datasets will be on par with those that have revolutionized our understanding of Mercury, Mars, and the Moon.

The 2023 field campaign served as both a test of the VERITAS instruments and a demonstration of what their improved capabilities will offer at Venus. Indeed, the campaign’s success demonstrated how VERITAS will make new discoveries and improve our knowledge of the planet’s past and present, and that it could lay the groundwork to optimize the science return of future Venus missions.

Author Information

Debra L. Buczkowski (debra.buczkowski@jhuapl.edu), Johns Hopkins Applied Physics Laboratory, Laurel, Md.; Jennifer L. Whitten, National Air and Space Museum, Smithsonian Institution, Washington, D.C.; Scott Hensley and Daniel C. Nunes, Jet Propulsion Laboratory, California Institute of Technology, Pasadena; and Marc Jaeger, Microwaves and Radar Institute, German Aerospace Center, Oberpfaffenhofen, Germany

Citation: Buczkowski, D. L., J. L. Whitten, S. Hensley, D. C. Nunes, and M. Jaeger (2026), Discovering Venus on Iceland, Eos, 107, https://doi.org/10.1029/2026EO260032. Published on 23 January 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.