PICO
Our session will provide a platform for cross-planetary discussion of the processes that generate and erode landscapes, create stratigraphy, and couple planetary surface dynamics to climatic and tectonic drivers. Considered processes could include aeolian, volcanic, tectonic, fluvial, glacial, periglacial, or as-yet "undetermined" ones.
We welcome contributions on Mars, Venus, Mercury, the Moon, icy satellites of the outer solar system, comets, and/or asteroids, to submit to our session. We believe that an interdisciplinary approach through sharing and discussing ideas across planetary borders is key in answering current questions and for the formation of new ideas, and thus we especially encourage cross-planetary contributions. We particularly welcome contributions from early-career scientists and geomorphologists who are new to planetary science.
PICO: Mon, 4 May, 16:15–18:00 | PICO spot 3
Slope lineae are bright, elongated streaks on Mercury’s slopes. Along with hollows, lineae are considered one of the youngest geologic features on Mercury. Past surveys suggested a qualitative relation between lineae and subsurface volatiles, implying that lineae could be geologic markers of the recent – and potentially ongoing – release of subsurface volatiles on Mercury. However, lineae have not been systematically mapped across Mercury and no quantitative analysis of their abundance, distribution, and geostatistical properties has been conducted. In [1], we use a deep learning-driven approach to scan through ~112,000 MESSENGER images and catalog slope lineae across Mercury to a) characterize their spatial distribution as well as their morphometric and spectral properties and b) use geostatistical and change detection approaches to explore whether lineae are active today – and whether they could be tied to recent or ongoing devolatilization on Mercury. Our analysis presents several arguments for a direct link between lineae formation and devolatilization: 1) lineae appear to feature a blue spectral slope, like hollows, 2) lineae largely source from hollows and hollow-like features, 3) lineae are predominantly hosted by small, young impact craters that penetrated volcanic deposits, i.e., in a geologic context that facilitates (vertical and lateral) access to subsurface volatiles, 4) lineae tend to cluster on equator-facing slopes, 5) lineae appear to be hosted by terrain with slightly higher (modelled) bi-annual peak temperatures at the surface and at shallow depth, and 6) several lineae occur on shallow slopes well below the angle of repose of dry regolith, suggesting the presence of volatiles as a fluidizing agent (more details are presented in [1]). We do not observe any lineae activity between 2011 and 2015, such as changed or newly formed lineae, implying that lineae activity occurs below MESSENGER’s spatial resolution and/or on timescales longer than ~4 years. Devolatilization-driven lineae activity is a hypothesis that will be scrutinized by the ESA/JAXA (European Space Agency, Japanese Aerospace Exploration Agency) BepiColombo spacecraft and the SIMBIO-SYS instrument suite (Spectrometer and Imaging for MPO BepiColombo Integrated Observatory SYStem) that are expected to initiate their science investigations in early 2027.
[1] Bickel et al. (2026). Slope lineae as potential indicators of recent volatile loss on Mercury. Communications Earth & Environment (in press).
How to cite: Bickel, V. T., Munaretto, G., Bertoli, S., Cremonese, G., Cambianica, P., and Vergara Sassarini, N. A.: Slope Lineae as Potential Geologic Markers of Recent Devolatilization on Mercury, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12154, https://doi.org/10.5194/egusphere-egu26-12154, 2026.
Lunar swirls remain one of the most enigmatic geological features on the Moon's surface. They appear as sinuous, high albedo patterns that are interwoven with “dark lanes” and stand out against the low-albedo background. Their unique spectral properties and strong correlation with lunar magnetic anomalies have attracted widespread scientific interest. The origin of lunar swirls is still debated. The prevailing solar wind deflection model suggests that pre-existing magnetic anomalies deflect incoming solar wind particles, leading to different degree of space weathering inside and outside the swirls and resulting in their distinctive spectral characteristics. As a key product of space weathering, nanophase iron (npFe0) directly reflects this differences inside and outside the swirls. In this study, we investigated the npFe0 content distribution of the swirl regions, offering a new perspective on the origin of lunar swirls.
In this study, we developed a model to estimate npFe0 content in lunar highland and maria soils using band ratio of remote sensing data based on laboratory-measured spectral data and npFe0 content of returned Apollo lunar samples. Then, this model was employed to the hyperspectral data acquired by Chang’E-1 Interference Imaging Spectrometer (IIM) to map the npFe0 content across five typical lunar swirl regions including Reiner Gamma, Mare Ingenii, Rima Sirsalis, Airy, and Firsov. Our results showed that npFe0 content in on-swirl regions is lower than that in off-swirl regions, indicating a suppressed space weathering effect within the swirl regions. Moreover, the relative npFe0 abundance between swirl dark lanes and surrounding off-swirl regions seems to be linked to different stages of space weathering. The distinct difference in npFe0 abundance between on-swirl regions and off-swirl fresh craters could be due to their different weathering processes. Additionally, we found a correlation between npFe0 abundance and the intensity of lunar magnetic anomalies in swirl regions. This indicates that the shielding effect of magnetic anomalies against solar wind particles may be influenced by the strength of the magnetic field. A potential relationship between npFe0 and OH-/H2O distributions within swirl regions also offer valuable insights into the solar wind-induced formation of lunar surface water. These findings support the hypothesis that incoming solar wind particles are deflected in swirl regions, leading to reduced space weathering on their surfaces.
How to cite: Liu, D., Li, Z., Zhang, Z., Zhang, H., and Li, C.: Formation of lunar swirls: Implications from Chang’E-1 Interference Imaging Spectrometer data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2886, https://doi.org/10.5194/egusphere-egu26-2886, 2026.
China's Tianwen-2 exploration mission is designed to perform comprehensive remote sensing, in-situ exploration, and sample return from the target small celestial bodies (2016HO3 and the main-belt comet 311P) through a series of operations including flyby, orbiting, landing, and sample collection. The mission will further investigate the formation and evolution of these target celestial bodies, their orbital dynamics, as well as correlations between the returned samples, meteorites, and data obtained from ground-based and remote sensing observations. Prior to the launch of the Tianwen-2 mission, we carried out comprehensive ground-based test to verify the detection capabilities of its nine onboard payloads and to assess the accuracy of the data they are designed to acquire.
Results show that all payloads have met the predetermined test objectives, demonstrating robust detection performance and reliable data validity. The images obtained by the Asteroid Medium Angle Camera and Narrow Angle Camera deliver images with a modulation transfer function (MTF) ≥ 0.2, capable of providing high‑quality imagery for morphological studies. The Asteroid Laser Detection and Ranging achieves a measurement accuracy better than 3cm, enabling precise acquisition of three-dimensional topographic data of the asteroid surface. Spectral data obtained by the Asteroid Multispectral Camera, Visible and Infrared Imaging Spectrometer, and Thermal Emission Spectrometer show good agreement with reference measurements from standard instruments, confirming their capability to identify various minerals. The Dust Multi-properties Analyzer module of the Asteroid Dust and Volatiles Analyzer successfully measures dust‑particle size, morphology, velocity, and mass. The Volatiles Ion Trap Analyzer module of the Asteroid Dust and Volatiles Analyzer can detect no fewer than 14 gas species, with concentration measurement accuracy better than 33%. Using a dual‑probe gradient magnetic‑field measurement method, the Asteroid Magnetometer effectively suppress spacecraft magnetic interference and acquired valid magnetic-field information of the detection target. The Asteroid CoreScan Radar can achieve penetration depths of 35m and 5m for its low-frequency and high-frequency channels, respectively.
How to cite: Li, C.: Ground Verification Test for Tianwen-2 Payloads, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2921, https://doi.org/10.5194/egusphere-egu26-2921, 2026.
[1] Bushuk M., Orton P.M., Holland D.M., Stanton T.P., Stern A.A., Gray C., Laboratory observations of ice–water interface morphodynamics in turbulent shear flow, J. Fluid Mech., 841, 614–646, 2018.
[2] Hsu K.S., Locher F.A., Kennedy J.F., Forced-convection heat transfer from irregular melting wavy boundaries, J. Heat Transfer, 101(4), 598–602, 1979.
[3] Perissutti D., Marchioli C., Soldati A., Time and length scales of ice morphodynamics driven by subsurface shear turbulence, J. Fluid Mech., 1019, A34, 2025.
How to cite: Perissutti, D., Marchioli, C., and Soldati, A.: Numerical assessment of celerity scaling laws for ice ripples in turbulent shear flows, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15361, https://doi.org/10.5194/egusphere-egu26-15361, 2026.
Throughout our Solar System, erosional processes reshape the surfaces of terrestrial and icy bodies, ranging from planets and moons to asteroids and comets. One such process is mass wasting, which transports loose material downslope driven by gravity, forming slides, avalanches or flows depending on conditions. Over the past decades, the role of volatiles in their formation has been debated. Our understanding of extraterrestrial mass wasting relies heavily on Earth analogues; however, these are mostly influenced by liquid water, which is not stable on other planetary surfaces. Yet, numerous extraterrestrial landforms indicative of mass wasting occur on planetary surfaces with (seasonal) ice or frost and on slopes too gentle for dry material to move unaided.
Ice sublimation is a potentially plausible mechanism for driving extra-terrestrial mass wasting, whereby solid volatiles directly transition into vapour. This can initiate flow and reduce friction between sediment particles. However, because of the lack of terrestrial analogues and the complexity of producing a usable numerical model, the mechanics of sublimation on sediment mobilisation, particle dynamics and flow behaviour remain unclear. Here, we investigate the roles of volatiles and environmental conditions on the mobility and dynamics of sublimation-driven mass wasting and the morphology of their deposits.
Over the past two years, we created flows driven by sublimating CO2 using flume set-ups in two low-pressure chambers at the Open University (Milton Keynes, United Kingdom) and Aarhus University (Aarhus, Denmark). Ambient pressure was varied stepwise from 0.1 to 1000 mbar to cover the
environmental conditions of a broad range of terrestrial and icy bodies. The mass flows consisted of dry ice mixed with either high-density (∼ 2600 kgm−3) or low-density granular material (410 - 1300 kgm−3), the latter was utilised to simulate reduced gravity. The results show that reduced ambient pressures increase the volume flux of gas, thereby enhancing the fluidisation, flow mobility and runout length, particularly for low-density flows. This suggests that terrestrial bodies with lower surface gravity have more mobile sublimation-driven flows. The behaviour of the mass flows varied noticeably with ambient pressure, showing transitions through different fluidisation regimes, each marked by distinct features. At high pressures (> 20 mbar), we observe steady flows. In the 20 - 1 mbar range, the flows start to exhibit bubbles, surges and outbursts. Below 1 mbar, turbulent behaviour emerges with a diffuse particle suspension flowing above a dense layer. These behavioural regimes are similar to the regimes observed in fluidised bed experiments and have been recognised in snow avalanches and pyroclastic density currents on Earth. Currently, we are analysing internal particle dynamics and velocities for these regimes using particle tracking software. Our research shows that sublimation can be an effective driver for mass wasting on terrestrial bodies with low ambient pressures, low gravity and the presence of volatiles other than water, and might operate in distinct fluidisation regimes.
How to cite: Diamant, S., Conway, S., Roelofs, L., Sylvest, M., Emerland, Z., Merrison, J., Iverson, J. J., Kleinhans, M., McElwaine, J., Patel, M., and de Haas, T.: Flow dynamics and behavioural characteristics of sublimation-driven granular flows under laboratory conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5111, https://doi.org/10.5194/egusphere-egu26-5111, 2026.
Mafic eruptions and their associated lava fountains are a widespread form of volcanism on both Earth and other planets. These eruptions typically produce scoria and spatter cones, or hybrids of the two, and both the characteristics of the associated tephra blanket and the morphology of the pyroclastic cone can forensically provide quantitative information about the eruption conditions. However, the morphology of a pyroclastic cone results from a complex interplay between syn-eruptive processes (e.g., volume of magma erupted, grain size of pyroclasts produced, syn-eruptive wind) and post-formation erosional processes. Thus, to quantitatively use cone geomorphology to inform on volcanic processes, the contribution of each of these factors must be disentangled. Specifically, here, we focus on the effect that atmospheric winds have at the time of the eruption in controlling the resultant cone morphology. We investigate Volcán del Cuervo, a pyroclastic cone in Lanzarote that has a complex morphology consisting of a distinct, elongated shape, with a second accumulation of pyroclastic material adjacent to the main crater. Here, we use an unnamed aerial vehicle to acquire a high-resolution, photogrammetrically derived digital elevation model (DEM). This DEM allows us to quantify the cone morphology and the precise location of the associated pyroclastic deposits. Samples were collected and associated grain size and density measurements were performed to characterise the pyroclastic material constituting the cone. Together, these data were then used in a ballistic trajectory model to constrain the critical wind and eruptive conditions required to form a secondary cone. Through transplanetary analogies, we conclude that secondary cone formation by this mechanism may bias remotely sensed detections of eruptive centres on planetary surfaces. Misinterpretation of these cones as separate eruptive vents would lead to an overestimation of past volcanism. Correct identification of secondary cones can instead provide direct constrains on eruption dynamics and past atmospheric conditions, including prevailing wind directions—an aspect that is particularly important in planetary environments where direct field validation remains unfeasible.
How to cite: Jones, T. J. and Pieterek, B.: Secondary pyroclastic cones created by syn-eruptive wind , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13591, https://doi.org/10.5194/egusphere-egu26-13591, 2026.
Landslides are key geomorphic features on Mars that record past climate conditions, slope stability, and volatile-driven processes. We present a regional inventory of 290 landslides between 20°S and 50°S on Mars, focusing on Late Amazonian events underrepresented in global databases. To map landslides, we used high-resolution Context Camera (CTX) (5 m/px) satellite imagery, and detailed morphometric analyses were performed using stereo-derived CTX Digital Elevation Models (DEMs) (6 m/px) satellite. The mapped landslides were classified into three major types: rock avalanches, slumps, and ejecta-type features. Our results indicate that landslide areas range from 0.26 to 174 km², with estimated volumes between 0.003 and 5.72 km³. The height-to-length (H/L) ratios, varying from 0.00013 to 0.268, reveal substantial differences in mobility and formation mechanisms. Approximately 40% of landslides at high southern latitudes display morphologies suggestive of basal ice lubrication or cryosphere involvement, supporting ice-facilitated movement mechanisms. Crater size-frequency distribution (CSFD) analysis constrains absolute model ages of these landslides between 3.50 and 480 Ma (Middle to Late Amazonian), indicating repeated mass-wasting activity over extended geological timescales.
Spatial correlation analyses between landslides and glacial features such as Lineated Valley Fill (LVF), Lobate Debris Aprons (LDA), and Concentric Crater Fill (CCF) reveal a strong association between ice-bearing terrains and enhanced landslide mobility. These findings indicate that subsurface ice acted as both a stabilizing and lubricating agent, reducing basal friction while promoting high mobility under favourable thermal conditions.
These results provide the first comprehensive dataset of southern mid-latitude landslides, filling a major gap in Martian landslide inventories. The morphometric variability observed in this region demonstrates that cryosphere-substrate interactions play a crucial role in shaping Martian slope processes. Our findings underscore the complexity of mass wasting dynamics and their strong linkage to past climate fluctuations, providing new constraints on the timing and preservation conditions of buried ice deposits across Mars' recent geological history.
How to cite: Yazıcı, D., Karagoz, O., Kenkmann, T., Carboni, F., and Görüm, T.: Inventory of young mass wasting events in Mars' Southern Hemisphere: Insights into characterization and formation mechanisms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-533, https://doi.org/10.5194/egusphere-egu26-533, 2026.
Glacier-like forms (GLFs) are one subtype of glacial features found on the Martian surface. They are located within the mid-latitudes of Mars (30-60 degrees) in both hemispheres. These features having formed within the Amazonian period during a period of higher obliquity than Mars' is at today which allowed for the preferential accumulation of icy material in the mid-latitudes. While previous studies have investigated the geographic controls on GLF formation, their former extent, and their former dynamics (Souness, et. al., 2012; Brough, et. al. 2016, 2019), the boundary conditions under which GLFs formed remain poorly constrained, particularly on a local-scale.
Our primary aim is to improve our understanding of how Martian GLFs formed and evolved with respect to their climactic and geomorphological setting using terrestrial rock glaciers as analogues. As there is still ongoing debate as to the formation dynamics of rock glaciers on Earth, be they permafrost-derived or derived from debris-covered glaciers, with the issue being that both start points can adequately describe the end-state of palaeo rock glaciers, we need to take an approach which acknowledges this issue of equifinality. Bayesian inversion is one such method that can do this. We start with the assumption that these GLFs represent permafrost-derived ice bodies where ground-temperature is a key boundary-condition for their formation. With this method, we use observed glacier geomorphology to reconstruct the former extent, volume, and thickness of the GLF to compute a posterior probability distribution for ground temperatures that are physically consistent with the reconstructed geometry of the palaeo glacier. We also consider near-surface air temperature as a secondary factor in accumulation feasibility.
Here we present our ongoing work in this effort. We manually demarcated the geomorphological constraints of multiple GLFs on Mars within GIS software based on identifiable geomorphology within the orthorectified imagery that mark the former maximum extent of the glacier, and extract morphometric data using the georeferenced HiRISE DEM. We then used the perfect-plasticity approximation to reconstruct palaeo ice-thicknesses and volume of the palaeo glacier. These morphometrics are then compared with modelled outputs for glacier deformation, employing Bayesian logic to constrain a boundary range of long-term mean ground temperature that would be compatible to produce the reconstructed glacier morphology. We also investigate several terrestrial rock glaciers in order to assess the accuracy and validity of our approach against measurable analogue examples, which further enables us to compare the dynamics of terrestrial and Martian glaciers.
References:
Brough, Stephen, Bryn Hubbard, and Alun Hubbard. 2016. “Former Extent of Glacier-Like Forms on Mars.”, Icarus 274 (August): 37–49. https://doi.org/10.1016/j.icarus.2016.03.006.
Brough, S., Hubbard, B., & Hubbard, A. (2019, 02). Area and volume of mid latitude glacier-like forms on mars. Earth and Planetary Science Letters, 507 , 10–20. Retrieved from https://linkinghub.elsevier.com/retrieve/pii/S0012821X18306903 doi: 10.1016/j.epsl.2018.11.031
Souness, Colin, Bryn Hubbard, Ralph E. Milliken, and Duncan Quincey. 2012. “An Inventory and Population-Scale Analysis of Martian Glacier-Like Forms.” Icarus 217 (1): 243–55. https://doi.org/10.1016/j.icarus.2011.10.020.
How to cite: Jones, M., Sam, L., Mullan, D., Rea, B., and Bhardwaj, A.: Investigating the formation conditions of glacier-like forms using Bayesian inversion. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20367, https://doi.org/10.5194/egusphere-egu26-20367, 2026.
Past studies of Martian-analogue landscapes in Antarctica have focused on the Dry Valleys [e.g., 1-3] with the goal of understanding the drivers and potential evolution of geomorphic features in predominantly “cold and dry” conditions. Here we present a new study of a Martian analogue-landscape from the seldom studied Schirmacher Oasis (SO, 70°45′30″S 11°38′40″E) which contains landlocked lakes, polygonal patterns attributed to seasonal thermal contraction and ice wedging, in addition to chloride surface deposits, and even desiccation features associated with the seasonal and long-term drying of the land-locked lakes [e.g, 4, 5]. The features of SO have been observed on Mars, including in terrains that have been dated to Early Mars (The Noachian Period, more than 3.6 Gya).
We investigated a number of land locked lakes using drone surveys, onsite characterization, and sample collection (Figure. 1). Preliminary results indicate that Schirmacher Oasis indeed provides a potential analogy for specific terrain on Mars, namely those associated with chloride deposits in lacustrine setting. Specifically, we propose that at least a subset of these terrains on Mars may have experienced a similar evolutionary history to that observed in SO; a fluvial, lacustrine and periglacial activity in a previously glaciated area. Studying such regions could help provide new insights into the geological and climatic evolution of Mars, particularly on regional scale, and in periods of transient warming under prevalent cold/icy conditions.
Figure 1: [Top] Geomorphological map of SO adapted from [6]. The legend has been slightly modified to highlight only a few selected units that are of relevance to this study. [Bottom] Satellite view of SO from Google Earth showing the sites visited and sampled in this study.
Acknowledgments: This work was carried out under an MOU between the Indian National Center for Polar and Ocean Research (NCPOR) and the Emirates Polar Program (EPP). The scope of work and collected materials were approved under the research permit MoES/CAG-EP/2025/45-ISEAlP1/23 from the Indian Government’s Ministry of Earth Sciences in full compliance with the Antarctic Treaty. We are deeply indebted to the support throughout from NCPOR under the guidance of Dr. Thamban Meloth, including all logistical support before travel and “on the ground” by the NCPOR team and Goa and at Maitri Station.
References: [1] Marchant, D. R., & Head, J. W. (2007). Icarus, 192(1), 187–222. [2] Tamppari LK, et al. (2012). Antarctic Science. 2012;24(3):211-228. [3] Heldmann, J. L. et al. (2013). Planetary and Space Science 85, 53-58. [4] Phartiyal, B., et al. (2011). Quaternary International 235, 128–136. [5] Dharwadkar, A., et al. (2018). Polar Science 18, 57–62. [7] Geological Survey of India (2006). Retrieved from: https://ncpor.res.in/files/40 Antarctic Exp/Schirmacher Oasis map.pdf.
How to cite: El-Maarry, M. R., Aldhanhani, O., Ray, Y., and Alsuwaidi, A.: Schirmacher Oasis, Antarctica: An Earth Analog for Glaciofluvial Landforms and Process on Early Mars?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15988, https://doi.org/10.5194/egusphere-egu26-15988, 2026.
The Curiosity rover continues its exploration of Mount Sharp, Gale crater’s ~5000 m-high sedimentary pile, and has been traversing for the past three years the Layered Sulfate unit (LSu), an interval initially characterized from orbit and thought to have recorded a global climatic transition toward the more arid conditions we observe nowadays on Mars. This unit, also informally known as the Mirador formation, is rich in sulfates and record mostly aeolian settings. Unexpectedly, the rover has also encountered numerous strata arguing for a recurring aqueous activity punctuating the overall arid, aeolian depositional environment.
Lately, Curiosity explored the “boxwork” unit, a high-interest region named after the orbital observation of “box-forming”, (deca-)meter-scale rectilinear features cropping out of the ground. Diagenetically-altered, fine-grained rocks making the most of the boxwork unit are probably of lacustrine origin, stressing out the importance of these aqueous conditions in the midst of the LSu. But when looking at the walls of this valley, made up of the Texoli, Mishe Mokwa and Cordillera buttes, we notably observe coarser-grained, erosion-resistant beds displaying a wealth of multi-scale sedimentary structures.
Among them are several occurrences of clinoform geometries that we sorted into three classes. Type 1 are characterized by inclined, sigmoidal to poorly cross-bedded strata, filling meter-scale, individualized lens-shaped bodies. Type 2 are characterized by inclined strata, sigmoidal but more cross-bedded strata. They are also observed filling lens-shaped bodies, but contrary to Type 1, these lenses are laterally stacked and cross-cutting each other’s immediate neighbor. Finally, Type 3 clinoforms occur in unconfined packages evidencing clearly sigmoidal, steeply-dipping (15-20°) and non-cross-bedded strata. While they are conformable with lower sub-horizontal layers pertaining to the bedrock, their top is mostly truncated by unconformable sub-horizontal layers. At the outcrop, the steeply dipping, sigmoidal strata also define a conspicuous lobate shape.
We interpret Types 1 and 2 clinoforms as the record of fluvial channels, with Type 1 a record of braided rivers and Type 2 a record of laterally migrating bars of a meandering river. Type 3 marks a conspicuous change and we interpret the vertical tripartite stratal pattern as bottomsets, foresets and topsets of a Gilbert-deltaic suite. These strata reflect fluvial to deltaic depositional settings with decreasing levels of energy from strictly fluvial, individual channels (Type 1), meandering channels (Type 2) and finally within a delta (Type 3).
These settings are in line with the quieter, presumably lacustrine, environment the boxwork unit’s strata likely origin from, and could represent the local sedimentary input. They contrast with the overall arid, aeolian structures observed to make most of the surrounding buttes and overall LSu. They nevertheless highlight a recurrence of humid episodes throughout the LSu. These events illustrate a more complex and unpredictable climatic pattern as Mars became colder and more arid.
How to cite: Caravaca, G., Mangold, N., Dromart, G., Rapin, W., Kite, E. S., Williams, R. M. E., Le Mouélic, S., Gasnault, O., Dehouck, E., Lanza, N., Vasavada, A., and Fraeman, A.: Fluvial to deltaic clinoforms observed by Curiosity in Gale crater’s Mount Sharp, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5639, https://doi.org/10.5194/egusphere-egu26-5639, 2026.
This study aims to isolate the effect of gravity on delta morphodynamics, a key uncertainty in interpreting Martian deltaic systems. Terrestrial deltas are commonly used as a framework to interpret deltas on Mars, yet the planet’s lower gravity fundamentally alters sediment transport processes and, consequently, delta morphology and evolution. Previous work has demonstrated that reduced gravity enhances net sediment transport for a given discharge and channel geometry, promoting a higher proportion of suspended sediment transport (Braat et al., 2024). However, the implications of these effects for delta morphodynamics have remained largely unexplored.
We conducted physical experiments in the Earth Simulation Laboratory at Utrecht University. Deltas were formed autonomously in a 3 cm-deep flume with a constant water (300 L/h) and sediment supply (2 L/h). Martian gravity was simulated by reducing the sediment particle weight through the use of low-density grains (nutshell particles, ~1350 kg/m³), thereby isolating sediment density as a proxy for gravitational effects. This approach generated higher mobility sediment and a greater fraction of suspended transport, consistent with expectations for Martian conditions. The resulting low-density deltas were compared to reference deltas formed with standard silica sand (~2650 kg/m³).
The experiments show that reduced sediment density leads to deltas with gentler equilibrium slopes and larger surface areas. The lower equilibrium slope requires little aggradation, and most of the sediment supply can be used for progradation. Low-density deltas also develop more pronounced levees, likely due to enhanced suspended sediment transport. These levees, together with minimal gradient advantages across the delta plain, result in reduced system dynamics: channels are more stable, and large-scale avulsions occur at relatively low frequencies. In contrast, normal-density deltas exhibit more frequent channel migration and avulsions. As a result, low-density deltas develop more irregular, multi-lobed planform geometries, whereas normal-density deltas tend to remain semi-circular or half-oval in shape.
These findings demonstrate that gravity alone can exert a first-order control on delta morphodynamics. Morphological characteristics commonly interpreted on Mars as indicators of fine grain sizes, high sediment mobility, or elevated discharges may instead arise from the effects of reduced gravity. Consequently, caution is required when interpreting Martian deltas solely based on terrestrial analogues.
How to cite: Braat, L.: Rethinking Martian Deltas: The Influence of Reduced Gravity on Delta Morphology and Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11314, https://doi.org/10.5194/egusphere-egu26-11314, 2026.
Diverse aeolian bedforms, including dunes, megaripples, and ripples, are migrating across the surface of Mars today, as driven by seasonally variable winds. While long-term sand flux and their regional boundary conditions have been well constrained for many dune fields, an understanding of annual sand transport variability (or consistency) is lacking. Here we provide a decadal-scale analysis of migration patterns for Martian aeolian dune systems and test the hypothesis that global dust storm (GDS)-related winds can influence bedform sediment fluxes.
Annual migration was assessed at select sites in High Resolution Imaging Science Experiment (HiRISE) orthoimages (0.25–1-m/pix) and digital terrain models. Displacements were recorded by manually mapping polylines along the dune crests in GIS over 3-8 Mars years’ worth of images. Sand fluxes were computed using slipface heights from the HiRISE topography, along with dune migration estimates – see Urso et al. 2017; Chojnacki et al. 2024. A total of 20 dune fields were analyzed from 85°N-45°S for Mars years (MY) 28-36, where sites were chosen based on data availability and long-term migration trends.
Migration rates for dunes ranged between 0.3-1.2-m/Earth year, with dune median heights of 6-17-m. Whereas median sand fluxes for sites ranged between 1-10-m3/m/yr over decadal-scale time periods, annual measurements may vary by an order of magnitude. The north polar erg dunes yield the highest rates despite being largely frozen and immobile during the northern autumn, winter, and spring. Here, the seasonal cap thickness and springtime defrost timing dictate how long winds can transport sand. There were notable sand flux maxima over the MY28-29 timestep and minima in MY34-35. The most notable events during these periods were the MY28 and MY34 global dust storms, which impacted the polar vortex, temperatures, and CO2 ice deposition. MARCI and HiRISE image mapping demonstrated that MY29 (early defrost) and MY35 (late) were endmembers in terms of spring defrosting. These events were attributed to the observed sand flux heterogeneity for some polar dune fields - see Chojnacki et al., 2024.
Equatorial or tropical latitude sites also showed significant deviations of sand transport rates, including during GDS years. Five dune fields showed reduced sand fluxes (33-49%) during the 2018/MY34 (~Ls 180-240°) GDS, relative to the prior year’s measurements. This reduction of nominal sand transport may be due to the depressed daytime surface temperatures or misaligned storm track directions (relative to nominal dune-forming winds) during the 2018 GDS, which were reported in the literature. In contrast, four dune fields were observed with increased fluxes (16-39%) in that GDS year. Elevated transport rates may relate to the alignment of dunes with dust storm corridors that experienced elevated wind shear or more localized factors. Finally, three sites showed no significant deviations in annual measurements, suggesting some bedforms may be in steady state in terms of sand transport. Climate factors such as global dust storms, seasonal ice cycles, and temperature variability appear to have a crucial role in sand availability and transport for Martian dunes; these factors demonstrate the complex interplay of boundary conditions on Mars.
How to cite: Chojnacki, M., Vaz, D., and Silvestro, S.: Interannual variability of sand dune fluxes and the influence of dust storms across Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14513, https://doi.org/10.5194/egusphere-egu26-14513, 2026.
Barchans are crescent-shaped dunes found in deserts with little sand, where winds blow continuously in one direction. They migrate in the downwind direction at speeds of several meters per year as sand eroded from the upwind slope is deposited on the downwind side. A characteristic feature of barchans is the localized sand outflow from their downwind-extending horns. Because barchans typically exist in clusters, this horn outflow can become sand inflow to barchans located further downwind, inducing sand-mediated interaction between upwind and downwind barchans.Most previous studies on barchan interaction have focused on direct contact interactions, i.e., collisions. However, it has recently been recognized that non-contact interaction mediated by sand transport can occur without collision. Studies on this type of interaction remain limited.This research focuses on non-contact sand-mediated interaction between upwind and downwind barchans. The interaction is investigated using a simplified crest line model [1]. This model is characterized by a small number of variables, which provides a distinct advantage in making theoretical analysis tractable.We obtain an analytical steady-state solution. The steady-state barchan shape is symmetric with respect to the sand supply source. The steady-state configuration consists of two parabolic solutions whose axes are laterally shifted due to sand inflow and connected at the supply source. Both the crest height of the steady-state barchan and the lateral displacement of the axes can be obtained analytically. We find that the steady-state barchan shape is determined by the migration velocity of the barchan and the sand inflow rate. In addition, the inverse proportionality between barchan height and migration velocity is theoretically confirmed in this study, a relationship well known in previous studies.The analytical solution shows good agreement with our previous numerical results. Our results provide deeper mathematical insight into non-contact sand-mediated interaction in barchan dune fields and offer a foundation for future studies on barchan collisions.
[1] L. Guignier. et al., Sand dunes as migrating strings, Physical Review E (2013)
How to cite: Navarro Yabe, S., Otoguro, K., Ninomiya, H., Shiraishi, M., and Nishimori, H.: The Effect of Sand-Mediated Non-Contact Interaction Between Barchans onTheir Steady-State Profiles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7823, https://doi.org/10.5194/egusphere-egu26-7823, 2026.
Aeolian megaripples develop on bimodal sands and are stabilized by an armoring layer enriched in coarse grains that developed on the crest. While size-selective transport is central to the segregation mechanism involved in megaripple formation, recent field observations indicate that shape segregation may also contribute to megaripple formation (Saban et al, Geosci. Lett., 2025). Here, we quantify the shape contrast between fine and coarse fractions of megaripples across multiple sites worldwide and investigate the physical mechanism that may explain it. Additionally, we investigate how ripple formation is affected by shape segregation through controlled wind tunnel experiments.
We analyzed samples from megaripple crests at multiple sites. Each sample was divided into sub-samples of fine fraction (<355µm) and a coarse fraction (>710µm), which represent the bimodal grain size distribution (GSD) of all the samples. Grain shape was quantified using a Circularity index (isoperimetric quotient), computed from a 2D projected grain outline derived from microscopy images. Grain outlines were produced by automated segmentation and were manually validated to ensure accuracy. Mineralogical composition and GSD were also measured and used as proxies for mechanical durability and abrasion history contrasts between the size fractions.
Across most sites, the coarse fraction is more angular (less circular) than the fine fraction, indicating a robust shape contrast between size fractions. To explain this pattern, we used a physically motivated combined index that accounts for the size contrast and the quartz contrast between the fine and coarse fractions. Sites where the fine grains are both relatively finer and more quartz-rich compared to the coarse fraction show a stronger shape contrast (i.e., fines are more circular). This suggests that abrasion history and mechanical durability influence grain shape.
Finally, we designed a wind tunnel experiment to isolate the role of shape segregation in the formation of nascent megaripple. We used mixtures of angular natural sand and spherical glass beads with the same grain size. These mixtures were subjected to wind above the fluid threshold until ripple formation. Spatial distribution analysis of grain shape at the end of the experiments reveals clear sorting patterns, driven solely by shape segregation, where angular grains accumulate on the crest and form an armoring-like layer.
How to cite: saban, L., Katra, I., and Yizhaq, H.: Beyond Size Sorting - Shape segregation in aeolian megaripple, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18079, https://doi.org/10.5194/egusphere-egu26-18079, 2026.
