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 3.0Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
