We performed the first laboratory study on the formation of molards by sublimation processes. On Earth, permafrost molards are cones of loose debris in landslide deposits that can be used as a marker for mountain permafrost retreat (Morino et al., EPSL 2019). They originate from ice-cemented blocks of sediment that are transported downslope within the landslide and melt to form conical mounds over time. Molard candidates have also been found on Mars in the ejecta flows of the one billion-year-old Hale Crater. These show similar morphology and spatial distribution to molards found on Earth (Morino et al., Icarus 2022). In contrast to Earth, these molards likely formed by sublimation, because water is not stable in its liquid form (Harbele et al., JGR 2001). To investigate how molards that formed by sublimation could differ from those formed by melting on Earth we performed experiments at the Open University’s Mars Chamber facility.

We created cylindrical (Ø13 cm) initial frozen blocks of sediment with either H₂O or CO₂ ice. To condense CO₂ gas within the sediment we modified the approach of Kaufmann and Hagermann (Icarus 2017). Because CO₂ has a faster sublimation rate than H₂O, this allowed us to investigate a wider range of sublimation conditions, and reveal processes which may be applicable to comets and/or icy satellites.

We let the initially frozen blocks of sediment degrade on a board in the Mars Chamber while monitoring them with a time-lapse photogrammetry system at a 15 minute interval. This allowed us to quantify the volume transport during the degradation phase. We performed experiments for both ice types at terrestrial and martian pressure for coarse sand, gravel, and JSC-Mars-1a (a Mars regolith simulant). We successfully recreated conical morphologies resembling terrestrial permafrost molards for coarse sand and gravel with CO₂ and H₂O ice under Martian pressure. JSC-Mars-1 fully degrades into conical mounds with CO₂ ice, but only partially degrades for H₂O ice under Martian conditions and does not degrade under terrestrial conditions.

The sublimation gas flux produced by the ice makes the largest difference in morphology between the experiments for the finest sediments. For the JSC-Mars-1a under martian pressure, the CO₂ ice cemented block degrades into a mound that is spread over a wider area than the same block under terrestrial conditions. We infer that the higher the gas production the more likely the grains are to be ejected, rather than just fall. Sublimation is not the dominant degradation process for the H₂O ice cemented JSC-Mars-1a block. All the blocks with coarse sand and ice degrade by sublimation processes. Yet because the grains are barely entrained by the gas flux (even at the highest forcing), the differences are more subtle. The gravel is not influenced by the sublimation gas flux. Our results reveal that sublimation can change the expected morphologies when the gas flux is able to entrain the sediment and has implications for interpreting sublimation pit morphologies on Mars and other planetary bodies where sublimation dominates (Mangold, Geomorphology 2011).

How to cite: Beck, C., Conway, S., Kaufmann, E., Sylvest, M., Pranckute, J., Patel, M., Hagermann, A., Chinnery, H., and Font, M.: Comparing sublimation and melting of CO2 and H2O ice-cemented sediments into molards: implications for martian surface processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22137, https://doi.org/10.5194/egusphere-egu24-22137, 2024.

On Earth, temperature decreases can cause the thermal contraction of ice-cemented ground. This forms polygonal networks of surficial fractures – called ‘thermal-contraction polygons’ (Washburn, 1956). Polygons exhibit different morphologies with time (Black, 1954): initially showing no relief (‘flat-centred polygons’, FCPs), their margins uplift with the growth of ice or sand wedges (‘low-centred polygons, LCPs); subsequently to wedge degradation, polygon margins then collapse into the wedge casts (‘high-centred polygons, HCPs).

On Mars, polygons of similar dimensions (~ 5-25 m in diameter) and morphologies (FCP/LCP/HCP) to those on Earth are commonly observed in the mid-latitudes. They are inferred to form by thermal contraction of ice-cemented ground (Mellon, 1997). Further, polygons in Utopia Planitia (UP) have been identified as ice-wedge polygons (Soare et al., 2021). This indicates a potential role of liquid water in UP during the Amazonian, at a period where the martian climate is thought to be non-conducive to the stability of surface liquid water.

Here, we seek to understand whether the characteristics of these ice-wedge polygons could be used to understand the subsurface properties of their substrate. Hence, we investigate the density and type (FCP/LCP/HCP) of polygons for three morphological units in UP, in the area (44-52°N 100-130°E) where polygons were identified as ice-wedge polygons by Soare et al. (2021).

In UP, we mapped two morphological units: the “sinuous unit” (elongated, sinuous features) and the “boulder unit” (covered in decametre-scale boulders). We then mapped polygons over the two units using a grid-based technique (Ramsdale et al., 2017).

We developed three parameters, that we infer reflect various properties of the ground: ρ_pol, reflecting the cementation of the substrate by ice; ρ_wf, reflecting the capacity of the substrate to form wedge ice; ρ_wp, reflecting capacity of the substrate to preserve ground ice.

The boulder unit has no polygons. Therefore, it must be a massive material, non-conducive to ice cementation. Its surface is an extensive field of boulders, and shows blocks shattered in place. It points toward a volcanic origin for the boulder unit. This result is consistent with studies that concluded to the presence of volcanic units in UP (e.g. Tanaka et al., 2005).

Our parameters show that the sinuous unit was an initially porous material that became cemented by ice, and underwent wedge formation. Therefore, the sinuous unit was deposited on top of the boulder unit, either as water-rich deposits from a large aqueous flow, which subsequently froze; or by condensation of water vapour from the atmosphere within porous sediment. Those two emplacement modes were suggested to have occurred in UP (e.g. Costard and Kargel, 1995; Séjourné et al., 2012). The sinuous unit was then degraded, exposing the underlying boulder unit.

These interpretations show that polygon characteristics can be used to unveil properties of their substrate. In our study zone in UP, it allowed us to link geomorphological units with specific geological processes, that were suggested to have occurred in UP. Therefore, the parameters we developed can be considered as additional tools to study the martian geology at the sub-regional scale.

How to cite: Conway, S., Philippe, M., Soare, R., and McKeown, L.: Martian thermal-contraction polygons as sounders of subsurface properties in Utopia Planitia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6348, https://doi.org/10.5194/egusphere-egu24-6348, 2024.

In glaciology, karstology, speleology or planetology, regular and periodic patterns are often
observed on dissolving, melting or sublimating solid substrates. One of the most common is
known as scallops, and consists of a cellular pattern of cups-like concavities surrounded by very
sharp crests. They can be found typically on the walls of limestone caves carved by underground
rivers. Yet very similar patterns form on the immersed part of icebergs, on high-altitude glaciers
or on the surface of meteorites during their entry into the atmosphere [1]. The similarity between
these patterns, despite the wide range of materials and hydrodynamic conditions, suggests a
common and general mechanism.
By comparing field measurements, numerical models and experiments, we propose a geometric
approach to explain the generic emergence of scallops [2]. We first characterize the morphology
of scallops found on the walls of a limestone cave thanks to 3D reconstruction by
photogrammetry, and demonstrate the presence of crests which can be seen as singular
structures. Then, we discuss the results of numerical models of interface propagation. They
allow us to interpret the appearance of crests and the formation of cellular structures as a direct
consequence of the fact that the erosion velocity is always directed along the normal to the
interface. Finally, we carry out a simple experiment in which patterns are created by dissolution,
on the surface of a block of salt, by a solutal convection instability [3]. In accordance with our
model, we report the emergence of a cellular pattern of concavities surrounded by sharp crests,
very reminiscent of natural scallops. It confirms that the formation of scallops is largely
independent of the details of the flow but rather results from a geometric mechanism. This
general mechanism can also explain the common presence of crests or spikes on other
geological patterns created by dissolution.

[1] P. Meakin, B. Jamtveit, Geological pattern formation by growth and dissolution in
aqueous systems. Proceedings of The Royal Society A 466, 659 (2010).
[2] M. Chaigne, S. Carpy, M. Massé, J. Derr, S. Courrech du Pont, M. Berhanu, Emergence of
tip singularities in dissolution patterns. Proceedings of the National Academy of Sciences
120(48), e2309379120 (2023).
[3] C. Cohen, M. Berhanu, J. Derr, S. Courrech du Pont, Buoyancy driven dissolution of
inclined blocks: Erosion rate and pattern formation. Physical Review Fluids 5, 053802 (2020).

How to cite: Chaigne, M., Carpy, S., Massé, M., Derr, J., Courrech du Pont, S., and Berhanu, M.: A geometric mechanism explains the shape of scallops and other sharp patterns in dissolution or melting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11769, https://doi.org/10.5194/egusphere-egu24-11769, 2024.

The NASA Perseverance rover has been traversing the Jezero western fan, a clastic succession on the western rim of Jezero crater, containing a series of rocks deposited between ~3.6-3.8 Ga that show evidence of basinward prograding fluvial-deltaic depositional conditions.

The lowest stratigraphy in the Jezero fan records a transition from igneous crater floor material to distal deltaic deposits. A transition to fluvio-deltaic and periodic debris flow deposition is recorded in the upper fan series: The Tenby formation sandstones are comparable to terrestrial meandering fluvial systems, planar-bedded coarse sandstones of the Otis Peak member overlie the Tenby formation, and a blocky unit of boulder deposits, referred to as the Boulder Unit tops the fan. To the west and north, the upper fan overlies a carbonate-bearing sandstone deposited on the crater rim: the Margin Unit. The contacts between these units have been obscured for much of the traverse, precluding detailed assessment of their stratigraphic relationships.  

Gnaraloo Bay, visited on Sols 959 – 1000 of the mission, is an erosional window where the upper fan intersects the Margin Unit. Erosion through three key stratigraphic elements presents an opportunity to unravel the relative timing relationships of the Jezero crater rim and upper fan. We present a stratigraphic framework built from observations in Gnaraloo Bay made from images collected with the Mastcam-Z stereo-camera system.

The majority of Gnaraloo Bay is formed of shallow dipping (<10°) packages of beds dipping either towards or away from the crater rim, part of the Margin Unit. Erosional truncations are present where packages are juxtaposed and one interpretation amongst others is that these are comparable to shoreline deposits in smaller terrestrial lacustrine settings.

An abrupt erosional boundary at Airey Hill separates outcrop of the Margin Unit and Tenby formation recording an abrupt transition to an initial phase of channelized upper stage flow directly on top of the Margin Unit, followed by deposition of increasingly thick migrating barforms.

The lower flanks of Vancouver Point expose sub-horizontal, well bedded, rough textured sandstones comparable to the Otis Peak member. The basal contact of these sandstones crosscuts and postdates both the Margin Unit and Tenby formation. The upper <5 m of Vancouver Point is topped by the Boulder Unit with a basal contact that downcuts the Otis Peak member beds, implying a time gap between member deposition.

The basal contact of the ~ 600 m linear ridge of the Boulder Unit at the Jurabi Point ridge crosscuts both the Margin Unit and Tenby Formation, indicating an erosional unconformity. The Otis Peak member is absent here, implying that it is not associated with Boulder Unit deposition, unconformably overlying the Margin Unit and Tenby formation, and pre-dating the Boulder Unit.

We interpret the stratigraphy at Gnaraloo Bay to record the initial deposition of channelized migrating barforms over rim-bounding margin deposits. This was followed by periodical fan progradation and subsequent deposition of sheets of the Otis Peak member which appear to have been shielded from erosion by late Boulder Unit debris flow deposition sourced from Neretva Vallis. 

How to cite: Barnes, R., Gupta, S., Jones, A., Horgan, B., Paar, G., Stack, K., Garczynski, B., Bell, J., Maki, J., Alwmark, S., Ravanis, E., Calef, F., Crumpler, L., Williford, K., Simon, J., Gwizd, S., Farley, K., Tate, C., Annex, A., and Kah, L.: A stratigraphic framework of the Jezero upper fan succession observed in an erosional window at Gnaraloo Bay, Jezero crater, Mars. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19143, https://doi.org/10.5194/egusphere-egu24-19143, 2024.

Jezero crater, which once contained a paleolake, is the investigation site of the current NASA's Mars 2020 mission. We modelled 9 water related processes in Jezero: 1) western inlet valley carving, 2) northern inlet valley carving, 3) crater flooding by only northern inlet and 4) by both northern and western inlets, 5) erosion of the eastern rim for the outlet, 6) water outflow from the crater, 7) outlet valley carving, 8) western delta deposition, 9) northern delta deposition. We claim that the northern inlet had participated in the crater flooding because it has terraces at the same height level as the breaching terraces in the outlet (breaching happened in 3 phases, as shown in [1]).

Measurements of channel sizes, valleys, deltas, eroded rim and outflowed water volumes were conducted in ArcGIS 10.8 using Mars 2020 Science Investigation CTX DEM Mosaic and HRSC Mars Chart DTM and corresponding ortho-mosaics.

We used flow discharge and sediment transport models by [2] to calculate minimum water and sediment transport timescales under constant bank-full discharge. For northern and western inlet-related processes we took 0.005 m as median grain size D50 (it is the biggest grain size reported for samples from the western delta front in [3] so far; considering that the delta front is characterized by fine-grained deposition, it is reasonable to assume that for the whole delta D50 could be equal and even exceed 0.005 m). For outlet and breaching-related processes we used 0.1 m as D50 (which is used to model breaching events, e.g. in [1] and [4]).

Various scenarios have been modelled; the most probable (according to our current knowledge) were analyzed.

Deposition of the deltas could happen simultaneously with the last incision of corresponding valleys; the amount of carved material from last incised valleys is approximately the same as deposited in deltas.

According to the modelled scenario, the eastern rim erosion lasts five times longer than the water outflow after breaching. This indicates that water discharged from the breach could not alone erode the rim and thus more water supply from inlets would be needed. However, the uncertainty of grain size calls this result into question.

Another conclusion is that the northern valley alone could provide enough water (~1000 km³) during its last incision to fill the crater before breaching (446 km³). Moreover, the last incised valleys were mostly carved after the breach; if not, they would have already provided enough water to fill the crater and the breaching would have already happened.

Comparison of water discharged after the breach (238 km³) with water needed to carve at least the last incision outlet valley (~4000 km³) shows that Jezero had to be an open-basin lake after breaching.

References:

[1] Salese, F. et al. (2020). Astrobiology, 20(8), 977–993.

[2] Kleinhans, M. G. (2005). Journal of Geophysical Research: Planets, 110(12), 1–23.

[3] Farley K., and Stack K. (February 15, 2023). Mars 2020 reports, Volume 2 - https://mars.nasa.gov/internal_resources/1656/

[4] Roda, M. et al. (2014). Icarus, 236, 104–121.

How to cite: Ovchinnikova, A., Jaumann, R., Walter, S. H. G., and Postberg, F.: Modelling the history of water in the Jezero crater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4701, https://doi.org/10.5194/egusphere-egu24-4701, 2024.

The Mars Science Laboratory (MSL) Curiosity rover continues to ascend Aeolis Mons in Gale crater, Mars, with the goal of characterising formerly habitable palaeoenvironments. Since September 2022, Curiosity has been traversing Gediz Vallis, a ~9-km long canyon incising into sulfate-bearing, sedimentary rocks on the northern margins of Aeolis Mons. Along the Gediz Vallis floor is the upper Gediz Vallis Ridge (uGVR), a quasi-sinuous, ~1.5 km long, ~80-100 m wide, ~5-30 m high, ridge. Upslope, uGVR is clearly set within an erosional channel, which disappears downslope. Near the Gediz Vallis outlet, uGVR transitions into the broader, lower GVR, recently interpreted by Bryk et al. (2023, AGU Fall Meeting) as a degraded alluvial fan. Since entering Gediz Vallis, Curiosity has undertaken an extensive long-distance imaging campaign of the eastern uGVR flank, acquiring multiple Mastcam and ChemCam Long Distance Remote Micro Imager (LD-RMI) mosaics. Additionally, in August 2023, Curiosity approached the ridge margins and conducted an in-situ investigation (“Region B”). A major objective of Curiosity’s uGVR campaign is to the determine the primary depositional conditions and palaeoenvironment of the ridge, which may record evidence for late-stage surface water flow in Gale.

Thus far, most uGVR exposures observed are formed of loosely consolidated, very poorly sorted, decimeter to meter-scale blocks. Most blocks are dark in tone and some are partially embedded within a finer-grained, matrix-like material. The blocks themselves are reworked, lithified, sedimentary rocks and many display a diversity of internal planar and/or cross-stratification, although others appear more massive. Where visible, bedding within the blocks is typically mm to cm in thickness. We used the Pro3D software package to measure mean diameter size of 70 blocks at Region B from stereo Mastcam images: 0.15±0.11 m; although we note that the largest block (~ 7 m diameter) occurs elsewhere. We also note that many blocks are fractured into multiple pieces, potentially due to post-depositional weathering processes. There is no obvious source bedrock from within the ridge that the blocks could be eroding from, consistent with the blocks being transported clasts, rather than erosional lag originating from in-situ bedrock. Generally, the clasts are very angular to sub-rounded, suggesting relatively limited transport and a local source bedrock.

The large clast size (cobble, boulder) and very poor sorting is consistent with deposition by debris flows: gravity-driven flows in which clasts are supported by a cohesive muddy matrix. The confinement of the uGVR to a channel argues against a completely unconfined flow, such as a drier landslide, forming the deposit. Post-depositional erosion has likely winnowed much of the finer grained fraction of the deposit. The sedimentary structures within the clasts (e.g., asymptotic cross-stratification) are similar to those in the Stimson formation, an aeolian sandstone, pointing to a potential upslope extension of Stimson, consistent with recent long-distance observations, though multiple sources are also possible. If our interpretation is correct, this would demonstrate that uGVR is providing access to lithologies transported from higher up Aeolis Mons.

How to cite: Davis, J., Dietrich, W., Mondro, C., Wilson, S., Caravaca, G., Williams, R., Thompson, L., Gasnault, O., Paar, G., Kite, E., Bryk, A., Banham, S., Gupta, S., Roberts, A., and Grotzinger, J.: The Upper Gediz Vallis Ridge at Gale Crater: Sedimentary Rock Clasts Transported by a Late-Stage Debris Flow on Mars?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5319, https://doi.org/10.5194/egusphere-egu24-5319, 2024.

The boxwork unit on Mount Sharp presents an interesting erosional geomorphic feature that will shortly be investigated by the Curiosity Rover. The boxworks have been interpreted as a decameter-scale rectilinear fracture pattern infiltrated by ground water subsequent to its formation [1]. It is hypothesized that a fluid-based fill cemented the area around the fractures leaving ridges of erosion-resistant material. Here we investigate the similarities between the Mt. Sharp boxwork unit, fracture patterns adjacent to the boxworks that do not exhibit a significant vertical expression, and a similar appearing decameter-scale fracture pattern on the lower unit of the Peace Vallis (PV) fan [2].

Unlike the raised topography of the Mt. Sharp boxworks, vertical expression along fractures in the PV lower fan unit is poorly developed and is only found in a few isolated locations. However, analysis of fracture patterns using the Symbolic Plane approach of Domokos et al. [3] shows that both areas have a similar underlying polygonal fracture pattern with resultant rectilinear forms. These forms average three junction angles at vertices and normally produce four sided blocks. This is similar to fracture patterns associated with Platonic attractors on both Earth and Mars [3]. In both areas, cells of a regular primary mosaic X-type nodes are sequentially bisected locally creating irregular T-type nodes in response to secondary fracturing. Both areas exhibit similar regularity measures (#T nodes/total # of X and Y nodes) that range from ~0.82 to 0.86.  The unit adjacent to the Mount Sharp boxworks that does not display raised ridges has a similar fracture pattern and regularity. The geometric similarity of all three areas suggests that they are likely to have formed from processes that produced similar stress fields.

We hypothesize for all three areas that aeolian erosion subsequent to fracture formation has removed some portion of the surface. However, in the case of boxworks, the contrast between the cemented and less resistant non-cemented material leads initially to the production of proto-boxwork rounded hollows. These hollows expand and eventually reach the more resistant rock of the infiltrated fractures resulting in high standing remnant ridges ~ 1-meter or less in height. If the boxwork groundwater hypothesis is correct, this suggests that limited groundwater may have been available on the Peace Vallis fan subsequent to its deposition sometime after ~3Ga [4]. The quantity of groundwater was insufficient to allow mineralization in all but a few isolated locations on the fan as well as in the non-boxworks fractured area adjacent to the boxworks unit.

 [1] Siebach and Grotzinger, JGR, 2014. [2] Oehler et al. Icarus, 2016. [3] Domokos et al., PNAS, 2020. [4] Scuderi et al., 2018 LPSC

How to cite: Scuderi, L. and Buie, A.: Geometric analysis of decameter scale fractures in the Peace Vallis fan lower Unit and Mt. Sharp Boxworks, Gale Crater Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13446, https://doi.org/10.5194/egusphere-egu24-13446, 2024.

Extensive fields of sub-kilometre- to kilometer-scale edifices have been discovered on Mars and the process of subsurface sediment mobilization has been proposed as their formation mechanism. However, as igneous volcanism might form similarly looking features, it is currently unknown how they formed. Previously it was shown that when low viscosity muds would be exposed over cold sandy surfaces under the reduced martian atmospheric pressure, such muds would behave in similar fashion as Pahoehoe lavas on Earth. This shows how difficult it can be to distinguish mud volcanoes from igneous volcanoes based on morphology alone.

However, the composition of the propagating mud as well as of the substrate might be crucial to the overall dynamics and the finite pattern of developed flow features on Mars. On the Red planet, a wide range of substrates is expected to be present globally; covering a transition from dry and warm unconsolidated regolith to permafrost with a higher content of ice. 

Therefore, to get a better understanding of the behavior of muds exposed to reduced atmospheric pressure and the resulting shapes of putative martian mud volcanoes, we performed a set of experiments, in which we studied the effect of warm, pre-cooled or continuously frozen substrates on general flow properties. We also considered different granular materials, transitional compositions or their spatial sequencing, using mainly silica sand, flour or pure water ice. 

All tested scenarios showed a significantly contrasting style in mud spreading over the various surfaces. The streaming style and finite morphology of the flows differed from fast, flat spreadings, with the levitation component of transport, to slow and narrow flows with a characteristic ropy pattern. The most important observed feature was an alternation of melting and recrystallization of the ice substrate, caused by interplay between the latent heat release and consumption in between the mud and substrate. Importance of ice in the substrate was also shown through rapidly extended boiling potential and prolonged flow ability of mud, probably due to combination of phase transitions in mud-permafrost and mechanical properties of the substrate itself. 

These findings are interesting for an evaluation of mud behavior in various environments occurring on Mars or other bodies within the Solar system where the sedimentary volcanism or cryovolcanism might be expected.

How to cite: Krýza, O., Brož, P., Fox-Powell, M., Sylvest, M., and Patel, M.: Complex flow of mud over cold and frozen surfaces in low pressure: Insights from physical experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8469, https://doi.org/10.5194/egusphere-egu24-8469, 2024.

Large reservoirs of methane exist in the subsurface seabed of Earth’s continental margins, both as solid gas hydrate/clathrate and in its dissolved and gaseous forms¹. The transport pathways for fluids involving gas, water, and sediments are referred to as cold seeps, allowing subsurface methane to rise on the seafloor. Cold seep systems generally have three structural components: 1) the fluid source, 2) plumbing systems, and 3) venting structures or seeping features at or near the seabed such as crater-like depressions called gas pockmarks, mud volcanoes, and hydrate mounds². Optical imagery suggests that these surface features on Earth resemble morphological features on Pluto’s landscape as well. Prior works studying Pluto’s geology suggest complex geological processes such as differentiation, suggesting the formation of an ocean-insulating clathrate layer, most likely methane-derived from organic materials in Pluto’s rocky core. Crater-like depressions on the surface of Pluto may form due to fluid seepage or blowout of methane hydrate reservoirs in regions where cold seep is prevalent. The morphology of seep-related craters is geometrically distinct and with different spatial distributions from those created by impacts³. To investigate the presence of seep-related craters on Pluto, we have surveyed bright-rimmed craters by CH₄ ice in Vega Terra to investigate possible methane seepage. Pluto Global Mosaic and DEM (300 m/pixel) were used to obtain and measure topographic profiles of craters > 18 km (slightly exceeding the transition diameter) using the Java Mission-planning and Analysis for Remote Sensing (JMARS v.5.3.0) software. The topographic profiles were grouped based on the classification of pockmarks in the Danish part of the central North Sea, categorized into U, V, W-shaped, and tabular depressions⁴. Our analysis shows that 70% of the studied craters exhibit asymmetrical shapes, with a distinctive prevalence of W-shaped geometry. The remaining 30% of craters displaying circular morphology were predominantly characterized by U and V shapes, and some tabular geometry. Our results further suggest that more than half of the craters in our analysis have undergone long-term evolution, potentially linked to long-term multi-episode fluid expulsion events. We also examine their surface composition using Linear Etalon Imaging Spectral Array (LEISA) data to discern potential compositional differences between craters resulting from impact events and those with non-impact origins. Our methane generation and pathway framework can allow a more accurate assessment of the interaction between geological methane and Pluto's atmosphere.

References

1. Boetius, A., Wenzhöfer, F. (2013). Seafloor oxygen consumption fuelled by methane from cold seeps. Nature Geoscience, 6(9), 725-734.

2. Talukder, A. R. (2012). Review of submarine cold seep plumbing systems: leakage to seepage and venting. Terra Nova, 24(4), 255-272.

3. Stewart, S. A. (1999). Seismic interpretation of circular geological structures. Petroleum Geoscience, 5(3), 273-285.

4. Andresen, K. J., Huuse, M., & Clausen, O.R. (2008). Morphology and distribution of Oligocene and Miocene pockmarks in the Danish North Sea–implications for bottom current activity and fluid migration. Basin Research, 20(3), 445-466.

How to cite: Manogaran, R., Poh, G., Ahrens, C., Traphagan, J., Mandt, K., and Karunatillake, S.: Putative Cold Seep Systems on Pluto: Analyzing Crater Morphology to Investigate Geological Sources of Methane, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14037, https://doi.org/10.5194/egusphere-egu24-14037, 2024.