An alpine glacier below Sunlight Peak in northwest Wyoming was first photographically documented in 1893, near the end of the Little Ice Age and during the time of industrialization. Since then, evolving technologies have been applied to observe this glacier and nearby discontinuous permafrost for studies spanning Earth, environmental, and planetary sciences. Surveys in the 21st century indicate negative mass balance coinciding with rising average air temperature. This paper reviews the geological and geophysical data on record for the Sunlight Glacier system, presents new results from a 2023 fieldwork campaign combined with remote sensing analysis and comments on likely scenarios of future evolution for this individual body of ice within a broader alpine cryosphere feeding the watersheds of western North America.

Martian debris-covered glaciers (DCGs) contain large quantities of water ice beneath a protective layer of rock and dust. Properties of the overlying regolith such as density and depth to ice are critical parameters for guiding in situ resource utilization (ISRU) of water and coring missions targeting potential habitats. Englacial debris layers that progressively outcrop at the surface could also provide access to enable shallow sampling of ice age sequences. To assess the capabilities of future drone-based ground-penetrating radar for detecting supraglacial debris thickness and near-surface stratigraphy-properties not resolvable from orbit with the Shallow Radar sounder-we conducted tests over two terrestrial analogs for Martian DCGs. Our platform consists of a DJI Matrice 600 Pro drone and a MALA Geodrone radar operating at a center frequency of 80 MHz. We detected a bulk glacier thickness of up to 28.5 m in Sourdough rock glacier (RG), Alaska, and 48.6 m in Galena Creek RG, Wyoming. We also resolved the supraglacial debris thickness, with a mean thickness of 1.5 m in Sourdough, and in Galena Creek, with a mean thickness of 0.8 m in extensional sections and 1.3 m in compressional sections. Furthermore, we detected layers outcropping at the surface in age sequences within the cirque of Galena Creek RG. We validated the internal reflectors with clutter simulations to discriminate genuine subsurface reflectors from off-nadir surface reflection "clutter." Finally, we provide recommendations for optimal survey design, including solutions to increase the signal-to-noise ratio and reduce clutter.

Martian debris-covered glaciers (DCGs) contain large quantities of water ice beneath a protective layer of rock and dust. This is supported by the observations from the Shallow Radar (SHARAD) sounding radar orbiting Mars. Properties of the overlying regolith such as density and depth to ice are critical parameters for guiding in-situ resource utilization (ISRU) of water and coring missions targeting potential habitats. Englacial debris layers that progressively outcrop the surface could also provide access to enable shallow sampling of ice ages sequences. Ground penetrating radar (GPR) is capable of imaging through the debris layer on the surface, allowing us to quantify debris thickness and composition, glacier thickness, ice purity, and the presence of englacial debris. Prior studies have demonstrated the potential of drone-based GPR for resolving these shallow features on terrestrial DGCs using an 80 MHz system (Aguilar et al., 2026), but higher-frequency surveys to better resolve the supraglacial debris and near-surface stratigraphy have not been tested. To address this gap, we conducted drone-based GPR tests at multiple frequencies at Galena Creek Rock Glacier, the best studied terrestrial analog for Martian DCGs. Our platform consists of a DJI Matrice 350 RTK drone and AeroZond LF radar operating at a center frequency of 100, 150, and 400 MHz. Given the complex topography, obstacles, and surface irregularities, we followed terrain at 3 m with a laser rangefinder altimeter. This altitude allows a high signal-to-noise ratio and reduces clutter, without compromising the safety of the drone. Preliminary results over previously imaged sites demonstrate that subsurface features were consistently resolved with greater detail than previous aerial systems. Our study demonstrates that drone-based GPR systems operating at multiple frequencies offer a robust method for surveying near-surface features in debris-covered glaciers. This approach can enhance our understanding of ice-rich landforms on Earth and inform the design of future aerial GPR platforms for Mars, particularly those targeting ISRU assessments and search of life missions. * This work was presented at the Summit on Drone Geophysics 2025. References: Aguilar, R. J., Holt, J. W., Christoffersen, M. S., Meng, T. M., & Nerozzi, S. (2026). Revealing the internal structure of Mars-analog glaciers from drone-based radar sounding. Journal of Geophysical Research: Planets, 131, e2025JE009208. https://doi.org/10.1029/2025JE009208

The last (Wisconsinan) glacial period was punctuated in North America by two glacial maxima, known as the Early and Late Wisconsinan glaciations. In Alaska, these maxima and their subsequent retreats have been the object of dating efforts to reconstruct local climatic events and compare them to global trends. Little is known, however, about the period of milder climate and reduced glacier extents that separated the Early and Late Wisconsinan maxima, likely spanning a significant portion of Marine Isotope Stage 3 (MIS 3). Here we provide a detailed sedimentological analysis for an area at the northern margin of the Chitina River Valley in the Copper River Basin, Alaska. There, a buried proglacial sequence composed of glaciofluvial stream deposits, glaciolacustrine muds, and ice‐proximal subaqueous fan deposits reveals ice‐free conditions at ∼39 ka. Our palaeodepositional reconstructions show that the local glacier, a tributary to one of the largest ancient south‐central Alaskan ice streams, had retreated to near its modern terminus position during early to mid MIS 3, indicative of a stadial–interstadial transition with modern‐like glacier termini. We attribute differences in facies stacking patterns to drastic fluctuations in local base level, driven by the formation and drainage of a regional ice‐dammed lake (Palaeolake Atna). Our results offer new constraints on Late‐Pleistocene glacial fluctuations in south‐central Alaska, including new MIS 3 glacial minima, and provide insights into the relationships between climatic fluctuations, ice extents, and associated landscape evolution in the Copper River Basin.

NASA’s Operation IceBridge employed airborne radar sounders in Alaska and adjacent northwestern Canada between 2012-2021 to measure the thickness of the region’s glaciers. Here we present the first comprehensive analysis of these data, providing over 5,500 linear-km of ice thickness and bed elevation measurements – constituting the greatest ice thickness inventory for this region to date. Aside from glaciers of the Saint Elias Mountains, radar bed returns are limited to expansive accumulation areas and glacier termini, distant from sources of off-nadir surface topography. Gridded measurements across Bering Glacier reveal a subglacial trough extending over 50 km from the glacier's terminus up to the Bagley Ice Valley, likely a subglacial expression of the Bering Fault. We find that many of the glacier termini successfully sounded by Operation IceBridge have overdeepened beds, which may offer insight into the potential extent of proglacial lakes and associated natural hazards given continued thinning and retreat. While the long-wavelength sounders employed by Operation IceBridge have proven capable of sounding through nearly 1500 m of temperate ice, radar surface returns from the flanks of the region’s mountain glaciers remain the greatest challenge to identifying glacier bed returns and retrieving ice thickness measurements. Simulating these returns in the survey planning may significantly improve the mapping success of future airborne radar campaigns.

Long-term historical records of glacier mass change are key to advancing understanding of glaciers' response to climate change and improving predictions of their future. Here, we use historical aerial photographs and new bed topography measurements to provide an 85-year record of glacier change on Kennicott and Root Glaciers in Alaska. At the glacier terminus, little change is observed in the two decades prior to 1957, followed by ongoing and accelerating mass loss with dynamically driven spatial variability. Glacier projections, constrained by these mass loss estimates, predict that Kennicott Glacier will lose 38 ± 14% to 63 ± 18% of its mass by 2100, relative to 2000, and Root Glacier will lose 38 ± 11% to 58 ± 12%, depending on the emissions scenario. These results differ by up to 22% from similar predictions made by projections calibrated from the past two decades of glacier change only. This highlights the importance of long-term glacier mass-loss records that help us better project far-reaching consequences of climate change related to sea level rise, water resources, natural hazards, climate, and culture.

Sít' Tlein (Malaspina Glacier), located in Southeast Alaska, has a complex flow history. This piedmont glacier, the largest in the world of its kind, is fed by three main tributaries that all exhibit similar flow patterns, yet with varying surge cycles. The piedmont lobe is dramatically reshaped by surges that occur at approximately decadal timescales. By combining historical accounts with modern remote sensing data we derive a surge history over the past century. We leverage the Stochastic Matrix Factorization, a novel data analysis and interpolation technique, to process and interpret large datasets of glacier surface velocities. A variant of the Principal Component Analysis allows us to uncover spatial and temporal patterns in ice dynamics. We show that Sít' Tlein displays a wide range of behaviors, spanning quiescence to surge with seasonal to decadal variations of ice flow direction and magnitude. We find that surges dominate the velocity dataset's variance (spanning 1984 to 2021), while seasonal variations represent a much smaller part of the variance. However, despite the regular surge pulses, the glacier lobe is far from equilibrium, and widespread retreat of the glacier is inevitable, even without further climate warming.

S & iacute;t' Tlein, located in the St. Elias Range, which straddles Alaska's Wrangell-St. Elias National Park and Kluane National Park in the Yukon, is the world's largest piedmont glacier. S & iacute;t' Tlein has thinned considerably over 30 years of altimetry, yet its low-elevation piedmont lobe has remained intact in contrast to the glaciers that once filled neighboring Icy and Disenchantment bays. In an effort to forecast changes to S & iacute;t' Tlein over decadal to centennial timescales, we take a data-constrained dynamical modeling approach in which we infer the parameters of a higher-order model of ice flow - the bed elevation, basal traction, and surface mass balance - with a diverse but spatiotemporally sparse set of observations including satellite-derived, time-varying velocity fields; radar-derived bed and surface elevation measurements; and in situ and remotely sensed observations of accumulation and ablation. Nonetheless, such data do not uniquely constrain model behavior, so we adopt an approximate Bayesian approach based on the Laplace approximation and facilitated by low-rank parametric representations to quantify uncertainty in the bed, traction, and mass balance fields alongside the induced uncertainty in model-based predictions of glacier change. We find that S & iacute;t' Tlein is considerably out of balance with contemporary (and presumably future) climate, and we expect its piedmont lobe to largely disappear over the coming centuries. If warming ceases, and surface mass balance remains at 2023 levels, then by 2073 (2173) we forecast a mass loss (expressed in terms of 95 % credible interval) of 323-444 km3 (546-728 km3). If instead surface mass balance continues to change at the same rate as inferred over the historical period, then we forecast a 2073 (2173) mass loss of 383-505 km3 (740-900 km3). In either case, the resulting retreat and subsequent replacement of glacier ice with a marine embayment or lake will yield a significant modification to the regional landscape and ecosystem.

We present Bedmap3, the latest suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60 °S. Bedmap3 incorporates and adds to all post-1950s datasets previously used for Bedmap2, including 84 new aero-geophysical surveys by 15 data providers, an additional 52 million data points and 1.9 million line-kilometres of measurement. These efforts have filled notable gaps including in major mountain ranges and the deep interior of East Antarctica, along West Antarctic coastlines and on the Antarctic Peninsula. Our new Bedmap3/RINGS grounding line similarly consolidates multiple recent mappings into a single, spatially coherent feature. Combined with updated maps of surface topography, ice shelf thickness, rock outcrops and bathymetry, Bedmap3 reveals in much greater detail the subglacial landscape and distribution of Antarctica’s ice, providing new opportunities to interpret continental-scale landscape evolution and to model the past and future evolution of the Antarctic ice sheets.

The Shallow Radar (SHARAD) instrument aboard Mars Reconnaissance Orbiter (MRO) has been conducting sounding operations of Mars' near surface for more than 16 years. Results of the SHARAD investigation have been well documented in the literature, with relatively high coverage density in the polar regions leading to some of the earliest scientific discoveries there. Data collection and ensuing surprises of SHARAD's primary and first extended science phases were the impetus for choosing the north polar region for producing a first 3D radar image. This early attempt was successful, producing the first 3D radar image of Mars' north polar layered deposits in Planum Boreum, and shortly thereafter a companion 3D radar image of the south polar layered deposits in Planum Australe. Subsequent work refined the 3D methodology used to produce these images, leading to a significantly higher quality 3D image of the former as well as the first 3D radar image of the debris-covered glaciers in the east-central portion of Deuteronilus Mensae (DM) in the mid-latitudes. Prior experience in terrestrial seismic data processing and analysis methods forms the basis of the 3D methodology used with Martian radar data, and has been indispensable in ongoing efforts to improve this methodology to further clarify the 3D images of the targets. The purposes of this article are to review 1) the SHARAD 3D work history and results, 2) the methodology developed and challenges encountered thus far in producing the SHARAD 3D images, 3) the broader impact on the processing and analysis of SHARAD data, and 4) current efforts and plans for producing follow-on SHARAD 3D images. Similarities and differences between orbital radar and seismic sounding and data processing are sprinkled throughout the article as reminders that the outcomes in this case are very much the product of cross-disciplinary knowledge and experience.

Abstract. Sít' Tlein in Alaska's St. Elias Range (briefly known as Malaspina Glacier) is the world's largest piedmont glacier and has thinned considerably over 30 years of altimetry, yet it's low-elevation piedmont lobe has remained intact in contrast to the glaciers that once filled neighboring Icy and Disenchantment bays. In an effort to forecast changes to Síit' Tlein over decadal to centennial time scales, we take a data-constrained dynamical modelling approach, in which we constrain the parameters of a higher order model of ice flow – the bed elevation, basal traction, and surface mass balance – with a diverse but spatio-temporally sparse set of observations including satellite-derived time-varying velocity fields, radar-derived bed and surface elevation measurements, and in situ and remotely sensed observations of accumulation and ablation. Nonetheless, such data do not uniquely constrain model behavior, so we adopt an approximate Bayesian approach based on the Laplace approximation and facilitated by low-rank parametric representations to quantify uncertainty in the bed, traction, and mass balance fields alongside the induced uncertainty in model-based predictions of glacier change. We find that Sít' Tlein is considerably out of balance with contemporary (and presumably future) climate, and we expect its piedmont lobe to largely disappear over the coming 150 years. We forecast a total mass loss at Sít' Tlein of between 500 and 1000 km3 of ice, a range that represents not only uncertainty in model inputs, but also in future warming scenarios. The resulting retreat and subsequent replacement of glacier ice with a marine embayment or lake will yield a significant modification to the regional landscape and ecosystem.

IntroductionHebrus Valles (HV) and Hephaestus Fossae (HF) are well-preserved Early Amazonian outflow channel systems carved into bedrock in SE Utopia Planitia, Mars (17-25 °N, 118-129 °E, Fig. 1). They exhibit a diverse set of morphologies indicative of formation by one or more liquid water outflow events (Christiansen, 1987; http://ntrs.nasa.gov/search.jsp?R=19870019962). However, little is known about their history, including both the origin and fate of the water and resulting sediments. This represents a significant gap in our understanding of geologic processes involving liquid water occurring in the Amazonian Period.Thanks to extensive coverage by recent datasets, it is now feasible to study the evolution of the HV-HF outflow channel systems with an integrated analysis of diverse and complementary data, including high-resolution visible and infrared imagery mosaics. We performed chronostratigraphic geologic mapping of the HV-HF region followed by a detailed reconstruction of the sequence of geological processes and events based on the identification of morphological and thermophysical facies. Then, we employed impact crater statistical analysis to determine geologic unit and outflow channel ages. Geologic mapping The oldest unit in the study area is the Nepenthes flow unit, a complex layered volcanic and sedimentary unit that was previously identified in the adjacent Nepenthes Planum region (Skinner and Tanaka, 2018; doi:10.3133/sim3389). On top of it lies the Utopia lower unit, which also corresponds to a sedimentary unit identified older geologic maps (Tanaka, 2005; https://pubs.usgs.gov/sim/2005/2888/; Skinner and Tanaka, 2018; doi:10.3133/sim3389). Moving up in the stratigraphic column, we found three additional units: the Utopia lowland unit, the Utopia lumpy unit, and the Utopia lobate unit. Based on morphological facies analyses and the observation of clear and distinct stratigraphic contacts, we determined that the Utopia lumpy unit and the Utopia lobate unit originated from subsequent and distinct tsunami-like events (e.g., Rodriguez et al., 2022; doi:10.1038/s41598-022-18082-2) transporting sedimentary materials across Utopia Planitia. Instead, the Utopia lowland unit and the Utopia lumpy unit are not delimited by clear stratigraphic boundaries, suggesting that they may be different facies of the same chronostratigraphic unit. Three younger units overlie the Utopia units. In the NE corner of the geologic map lies the Elysium volcanic unit, which consists of volcanic flows related to Elysium Mons volcanic activity. To the south, we identified two additional volcanic and tectonic units: the Elysium platy unit and the Elysium chaos unit. Figure 1: Chronostratigraphic map of the HV-HF region. Age measurements We conducted impact crater size-frequency distribution (CSFD) analyses on each chronostratigraphic unit by recording the locations and diameters of approximately 10000 impacts. We find formation ages for the Utopia units ranging from 2.9 Ga to 3.4 Ga (Fig. 2), placing the ages of units carved by channels between the Late Hesperian and Early Amazonian epochs. We also found evidence of resurfacing events occurring across three of the Utopia units at 2.2-2.3 Ga and a younger resurfacing event occurring at 1.7 Ga (Fig. 2). We interpret these events to be a combination of erosion of the Utopia Planitia plain-forming terrains and possible accumulation of volcanic sediments mantling the eastern half of the study area, perhaps associated with a peak in volcanic activity around 2-2.5 Ga (Platz and Michael, 2011; doi:10.1016/j.epsl.2011.10.001). Stratigraphy tells us that the Hephaestus Fossae and Hebrus Valles channel systems are necessarily younger than the surfaces they cut through, indicating that the channels must be younger than ~2.9 Ga. CSFDs within HV and in its distributary region yield ages of 1.8 Ga and 1.9 Ga, respectively (Fig. 3). Similarly, buffered crater counting of HV and HF yields ages of 2.1 Ga and 1.8 Ga, respectively (Fig. 3). These results confirm that the channels formed in the second half of the Early Amazonian about 1.5 Gy after the formation of the Utopia units, meaning that surficial aqueous activity in Utopia Planitia was occurring well into the Amazonian period.Figure 2: CSFD analyses for the Utopia units with model formation ages (red) and resurfacing events (blue). Figure 3: CSFD analyses for the HV and HF channels showing their model formation ages. Origin and evolution of the outflow channelsThe HV and HF channels originate from two deep pits within the Utopia lower unit (Fig. 1). We identified several elongated ridges protruding through the floor of these pits, which we interpret as remnants of magmatic intrusions that cracked the cryospheric seal of an ancient pressurized aquifer, as previously proposed for morphologically similar features in Cerberus Fossae (Head et al., 2003; doi:10.1029/2003GL017135). The morphology of the pits and the proximal sections of the channels are entirely compatible with morphologies observed in flume experiments where subsurface water discharge from a pressurized aquifer cause erosion and formation of terraces and deep source depressions within poorly consolidated sediments (Marra et al., 2014; doi:10.1002/2014JE004701). We reconstructed the initial phases of pit formation and channel incision in Fig. 4.The pressurization of the aquifer can be explained by two mechanisms: heating of the aquifer by a magmatic intrusion that then cracked the cryospheric seal (Delaney, 1982; doi:10.1029/JB087iB09p07739) and/or the presence of an hydraulic gradient in an extensive cryospherically-sealed aquifer (e.g., Palumbo and Head, 2020; doi:10.1029/2020GL087230.). We find that both mechanisms could have contributed to the water discharge, and that the magnitude of their individual contributions depended on the permeability of the aquifer, because low permeability is required to maintain pressurization in the case of magmatic heating. We also note that the magmatic driver of pressurization and cryospheric cracking implies that the water release must have been modulated by magmatic activity, and thus we find it likely that multiple long-lived water discharge events occurred in this region until magmatic activity waned. Figure 4: Step by step diagram of initial pit and channel formation. (left) A cryospheric seal confines a deep aquifer. Polygonal fractures are already present on the surface. (center) Magmatic intrusions crack the cryospheric seal leading to ponding of water, the formation of pits, and initial downslope flow on the surface. (right) Continuing water release deepens the source pits and carves channels in HV and HF, often following pre-existing fractures.

Ruth Glacier is situated in the Central Alaska Range, with the Don Sheldon Amphitheater comprising much of its broad accumulation area, directly adjacent to North America's tallest mountain, Denali. From there it funnels through the ‘Great Gorge,’ flanked by steep valley walls reaching over 1500 m. We combine airborne and ground-based radar measurements of ice thickness with satellite-derived surface velocities to constrain ice flux above and below the gorge, and employ a mass conservation approach to estimate the glacier's thickness within the gorge. We measure ice thickness in the amphitheater to reach 950 m, and estimate centerline thickness in the gorge to range from 610 to 960 m. Our estimates are up to two times greater than those suggested by global models, and allow us to confirm that the Great Gorge rivals Hells Canyon as the deepest gorge in North America. We found that the geometry of the gorge prevents radar measurements of ice thickness there since returns from the subglacial valley walls would precede and potentially occlude nadir bed returns. The same may be true of other unmapped mountain glaciers; however, thickness may be determined using appropriately located flux gates where radar sounding is feasible, combined with mass conservation methods.

Debris-covered glaciers and rock glaciers have been increasingly studied in recent years because of the role they play within local watersheds, glacial ablation models due to climate change, and as analogs for buried ice features on planetary bodies such as Mars. Characterizing the supraglacial debris layer is a large part of these efforts. Geophysical exploration of debris- covered glaciers has mostly excluded active seismic methods, with the exception of refraction studies, due to the attenuating properties of the debris cover and field survey efficiency. We evaluate the accuracy, field efficiency, and effectiveness of seismic refraction, reflection, and surface-wave surveys for determining the elastic properties of the debris layer and any underlying layers on debris-covered glaciers using sites from Sourdough Rock Glacier and in the Malaspina Glacier forelands in Southcentral Alaska. We compare our seismic results with our results from ground-penetrating radar. Our results indicate that the interface between the debris layer and the ice can be imaged using seismic reflection methods, and that multi-channel analysis of surface waves (MASW) can provide insight to the variability of the shear-wave structure within the debris layer. We image an ultra-shallow seismic reflection from the bottom of the loose debris layer using ultra-dense receiver arrays. This study also presents results using multi-channel analysis of surface waves (MASW) on a debris-covered glacier, which we find could be a valuable addition to the toolbox of future geophysical investigations on these landforms.

Since November 2006, the Shallow Radar (SHARAD) aboard the U.S. National Aeronautics and Space Administration's (NASA's) Mars Reconnaissance Orbiter (MRO) has been conducting subsurface sounding operations from orbit around Mars. This extended campaign has provided tens of thousands of radar profiles of Mars shallow subsurface, with coverage density in some regions having become sufficient for performing three-dimensional (3D) imaging. Adapting methods and tools used to produce, analyze, and interpret terrestrial seismograms, we have produced and studied fully imaged 3D radargrams in Mars' polar and mid-latitudes regions. In this report, we provide some background on the SHARAD instrument, summarize the methods and tools used in creating 3D radargrams from SHARAD data, and present example views from the latest 3D radargram in the north polar region known as Planum Boreum (PB).

Ground penetrating radar (GPR) is a valuable geophysical technology for imaging the interior of debris-covered glaciers (DCGs) on Mars and Earth. The Shallow Radar (SHARAD, 15-25 MHz) sounder onboard NASA’s Mars Reconnaissance Orbiter confirmed the bulk composition of the DCGs at the mid-latitudes of Mars is water ice [1]. However, internal structure and debris layer thickness, which are of interest for paleoclimate studies and in-situ resource exploration, respectively, are not obtainable with this instrument and would be challenging for any orbital platform [2, 3].On Earth, GPR has been employed over terrestrial analogs to understand the basic relationships between the composition, structure, flow kinematics, and morphology of similar landforms [4, 5]. This geophysical method penetrates through the debris layer on the surface, allowing for the quantification of the debris thickness, total glacier thickness, ice purity, and the presence of englacial bands. Traditional surface-based GPR has a high signal-to-noise ratio (SNR), but involves slow, manual operations with bulky equipment that renders it less suitable than robotic platforms for future Mars exploration missions.To address this challenge, we tested a drone-based GPR at two DCGs, Sourdough, Alaska, and Galena Creek, Wyoming. The platform consists of a MALA Geodrone 80 GPR system mounted on a DJI Matrice 600 Pro (Figure 1). To maintain a constant speed and altitude over an uneven surface, we use a UgCS SkyHub terrain-following system consisting of an altimeter and a distance sensor for obstacle avoidance. The GPR antennas should be as close to the ground as possible to maximize the SNR, so we conducted surveys starting at 1.5 m above the ground. However, due to the roughness of the terrain, steep slopes, and the presence of large boulders, most of the surveys have been performed at altitudes between 2 and 3 m to reduce the risk of collision, at a flight speed between 0.5 m/s and 1 m/s.Our findings suggest that the drone-based GPR can resolve the debris/ice with acceptable SNR and thus accurately measure the debris thickness. Also, it is possible to detect the bedrock in sections where the glacier is thinner. Additionally, drone-based GPR also resolved these reflectors at the cirque of Galena Creek, where surface-coupled GPR had identified englacial debris bands.In conclusion, our system is a promising method for surveying rock glaciers on Earth. As for planetary exploration, the study of robotics-based radar platforms aligns with the interests of developing uncrewed missions to Mars. For instance, the Mars 2020 mission includes a GPR as part of the instruments onboard the Perseverance rover, and Ingenuity, a successful demonstration of autonomous powered flight on Mars. References [1] Holt, J. W. et al., Science, vol. 322.[2] Baker D. M. H.and Carter L. M. (2019) Icarus, vol. 319.[3] Aguilar, R. et al. (2024) LPSC LV, Abstract #2479.[4] Petersen, E. I. et al. (2018) Geophys. Res. Lett., vol. 45.[5] Meng T. M. et al. (2023) Remote Sensing, vol. 15.Figure 1. DGPR operations at Galena Creek Rock Glacier, Wyoming. The GPR MALA Geodrone 80 (white box) is mounted on the DJI M600 Pro drone. The length of the antennas is 1.04 m, with a separation of 0.53 m.Figure 2: Radargrams acquired at lower Sourdough Rock Glacier. (a) Drone GPR at 80 MHz, ground tracks represented with the yellow line in Figure 1a. (b) Surface-based PulseEkko GPR at 50 MHz, ground tracks represented with the red line in Figure 1a. (c) and (d) are insets of the debris-ice interface from Figure 2a and Figure 2b, respectively.

One of the key components of this research has been the mapping of Antarctic bed topography and ice thickness parameters that are crucial for modelling ice flow and hence for predicting future ice loss and the ensuing sea level rise. Supported by the Scientific Committee on Antarctic Research (SCAR), the Bedmap3 Action Group aims not only to produce new gridded maps of ice thickness and bed topography for the international scientific community, but also to standardize and make available all the geophysical survey data points used in producing the Bedmap gridded products. Here, we document the survey data used in the latest iteration, Bedmap3, incorporating and adding to all of the datasets previously used for Bedmap1 and Bedmap2, including ice bed, surface and thickness point data from all Antarctic geophysical campaigns since the 1950s. More specifically, we describe the processes used to standardize and make these and future surveys and gridded datasets accessible under the Findable, Accessible, Interoperable, and Reusable (FAIR) data principles. With the goals of making the gridding process reproducible and allowing scientists to re-use the data freely for their own analysis, we introduce the new SCAR Bedmap Data Portal (https://bedmap.scar.org, last access: 1 March 2023) created to provide unprecedented open access to these important datasets through a web-map interface. We believe that this data release will be a valuable asset to Antarctic research and will greatly extend the life cycle of the data held within it. Data are available from the UK Polar Data Centre: https://data.bas.ac.uk (last access: 5 May 2023​​​​​​​). See the Data availability section for the complete list of datasets.

We assess the composition and geometry of four individual rock glaciers in Alaska, Wyoming and Colorado by measuring their radio wave speed and applying these results to ground-penetrating radar depth corrections and dielectric mixing models. Our method includes a correction for subsurface reflector dip angle, which we show can lead to an incorrect determination of wave speeds using common midpoint configurations. By observing the radar properties of the rock glaciers and their supraglacial debris, we find that some of the sites exhibit nearly pure ice cores, and all of the sites indicate volumetric ice fractions >50%. These results have implications for terrestrial glaciology and hydrology because the present ice volume is connected to past ice accumulation and subsurface ice preservation, which may affect the future availability of alpine water resources. An understanding of the processes that govern rock glacier evolution over a wide range of latitudes and elevations will also contribute to the exploration of planetary surfaces such as Mars, which hosts a significant population of debris-covered glaciers. Our subsurface composition and geometry estimates will inform simulations of rock glacier formation and evolution to test hypothesized ice origin mechanisms along with the preservation of climate signals.