The Taurus-Littrow Valley, location of the Apollo 17 landing site, hosts recent, late-Copernican geomorphological landforms and tectonic structures, namely the Light Mantle avalanche deposit and the Lee-Lincoln lobate scarp. The Light Mantle deposit represents a unique case of a hypermobile avalanche on the Moon (El-Baz 1972; Schmitt et al. 2017). The Lee-Lincoln lobate scarp is the surface expression of a recent thrust fault (Watters et al. 2010), which is considered to be the source of strong seismic shaking throughout Taurus-Littrow Valley (van der Bogert et al. 2012, 2019), and potentially still active (Watters et al. 2019).

The Light Mantle represents the only extraterrestrial landslide for which an absolute age is provided (70-110 Ma), thanks to the Apollo 17 returned samples (e.g., Schmitt et al. 2017). Therefore, the Light Mantle deposit can be used as a geomorphological marker and time constraint for surface changes that occurred since its emplacement. By applying the principle of superposition, surface changes superposed on the Light Mantle deposit, and on the slope from which it was generated (the NE-facing slope of the South Massif), must post-date the landslide event. For example, small scale grabens (10-20 m wide) associated with the Lee-Lincoln lobate scarp are found superposed on the Light Mantle unit (Watters et al. 2010). These troughs likely formed less than 50 Ma and are thought to be generated by the flexural bending of the hanging wall (Watters et al. 2010, 2012). Similarly, boulder tracks, whose survival time is estimated to range up to 35 Ma (e.g., Arvidson et al. 1976; Kumar et al. 2019), are found on the NE-facing slope of the South Massif, therefore evidence that boulder falls have occurred after the Light Mantle landslide event.

Here, we extend the body of evidence of surface changes that have affected the South Massif since the emplacement of the Light Mantle deposit. We map boulder tracks, areas of disturbed regolith, linear slope structures, and other structures associated with the summit of the South Massif. We identified features (i.e., slope structures oblique to contours, the Nansen Moat and the trough at the NE-base of the Sout Massif) directly related to back-thrust faults associated with the Lee-Lincoln thrust fault, which are re-activating the buried fault that bounds Taurus-Littrow Valley; we identified other features (i.e., crestal graben-like structures, slope structures parallel to contours) that derived from gravitational adjustment following basal slope support removal due to back-thrust faulting. Moreover, the overlapping relationships between the boulder tracks and regolith disturbance suggests that continuous slope deformation has been affecting the NE-facing slope. We attribute the efficiency of the process to repeated ground-shaking perturbation, which maintains the slope in a perpetually unstable state.

We conclude that the NE-facing slope of the South Massif has been recently and continuously affected by slope deformation processes. We suggest that the efficiency of these processes is the product of lasting, and perhaps ongoing, effects of activity of the Lee-Lincoln thrust fault, coupled with the influence of the subsurface geometry of the valley inherited from the impact basin formation.

How to cite: Magnarini, G., Grindrod, P., and Mitchell, T.: Slope Deformation Associated with Recent Tectonism and the Lasting Effect of Local Subsurface Geometry in the Taurus-Littrow Valley, Apollo 17 Landing Site., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1320, https://doi.org/10.5194/egusphere-egu23-1320, 2023.

Geomorphological analogues provide a valuable perspective for understanding planetary volcanic structures, landforms, and processes. Arabia Terra, Mars contains numerous collapse structures that are somewhat controversially interpreted as calderas. This work aims to use planetary analogues to shed further light on possible martian caldera collapse and volcanic processes.

The project had a focus on a population of underrecognized ancient volcanic constructs that associated with explosive and effusive volcanism, termed “plains-style caldera complexes” (Michalski and Bleacher, 2013), that are present within the Arabia Terra and perhaps across the Noachian-Hesperian crust on Mars. These features are characterised by deep crustal collapse, presence of flow deposits, potential pyroclastic materials, and more importantly, without a pronounced central edifice. Notable examples of the plains-style caldera complexes includes: Eden Patera (33.5°N, 348.8°E), type-locality of the plains-style caldera complexes; Siloe Patera (35.3°N, 6.55°E), which presents two overlapping classic piston-type caldera collapse; and Hiddekel Cavus (29.4°N, 16.2°E), a narrow, cone-shaped depression with extremely high depth/diameter ratio. In this project, besides working on Martian satellite imagery and topographic data, terrestrial analogue study was also a useful tool when analysing caldera floor geomorphology at Eden Patera. 

The Hawaiian volcanoes have previously been used as analogues for certain volcanic processes on Mars (Mouginis-Mark et al., 2007; Hauber et al., 2009). Though the Hawaiian volcanoes formed through different volcanic styles than the plains style caldera complexes, they nonetheless provide insight into key processes. At Kīlauea volcano, Hawaiʻi, the caldera collapse and volcanic deposits were associated with Hawaiian-style effusive eruption of basaltic lava, accompanied by minor explosive eruptions (Stovall et al., 2011; Patrick et al., 2020). Kīlauea Iki and Halemaʻumaʻu, the pit craters of Kīlauea, were considered as potential terrestrial analogue for (1) the “black ledge” formation (chilled lava lake margin feature) and (2) isolated “islands” of pyroclastic materials on the caldera floor at the Eden Patera, and both features are important evidence supporting a volcanic story, as well as both effusive and explosive activities of the Eden Patera caldera complex.

Nonetheless, potential analogue for caldera collapse mechanism was once again identified at Kīlauea Halemaʻumaʻufor an unnamed cavus of possible volcanic origin within the mid-Noachian to Hesperian plain of Xanthe Terra, Mars (Tanaka et al., 2014). Both the Hawaiian pit crater and Martian cavus are deep depressions with steep scarps, overlying a region of extensive concentric faults and fractured crust, making Kīlauea a good candidate for future analysis as a terrestrial analogue for caldera features of the plains-style caldera complexes on Mars.

How to cite: Chu, Y. Y. and Michalski, J. R.: Geomorphic study of caldera features on Mars with the help of Earth analogues, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4080, https://doi.org/10.5194/egusphere-egu23-4080, 2023.

 Landscape Evolution Models (LEM) play a vital role in illustrating the complex landscape
responses to various geomorphic processes. These models favour replicating various evolution
processes over an extensive range of temporal and spatial scales. LEMs are also suitable for
simulating the effect of volcanic activity on landscape features. Olympus Mons, the largest
shield volcano in our solar system, acts as the perfect landform for this analysis. Tharsis
Volcanic Landforms on Mars, such as Olympus Mons and Tharsis Montes, are considered
analogues of basaltic shield volcanoes on Earth. The shield volcanoes of Tharsis are compared
to terrestrial Hawaiian volcanoes and Deccan volcanism and are often interpreted as hotspot
plume volcanism. The stream power incision model (SPIM) is used in landscape evolution
models to simulate river incisions. In this study, we utilised LandLab software to perform
numerical evolution modelling on Olympus Mons. The initial topography of the research
region is established using a DEM, and the maximum elevation of Olympus Mons is 21241.0
metres. The erodibility (Ksp) value, based on the lithological and climatic conditions, is taken
as 1 𝑀𝑎– ¹ under Hawaiian conditions considering the basaltic type rock property of Olympus
mons. With a concavity index value of 0.5 and zero upliftment, the model is run for 100000
years to observe its evolution. Our results reveal a change in the maximum elevation of 21241.0
to 21179.68, i.e., 124 m, due to the process of erosion. The results give an idea about how the
original volcanic landform, like that of Hawaii, must have shaped into the present landform
due to various geomorphic factors. 

How to cite: Sonowal, S., Narayan M, U., Ahmad, A., and Nair, A. M.: Landform Evolution Modelling of Volcanic Landforms using Landlab: A case study of Olympus Mons, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13051, https://doi.org/10.5194/egusphere-egu23-13051, 2023.

Granulometry, shape, and chemical composition analyses of the sediments studied by the Opportunity rover along its entire 45-km-long traverse have been used to classify sediments and provide information about their origin and depositional processes.

We have conducted granulometry and shape analyses of 179 sediment targets visible in MI images [1]. To facilitate the analyses, we have used the PADM algorithm - a semi-automatic tool for particle detection, measurement, and analysis [2]. This allowed identification of more than 70000 individual grains. For chemical composition analysis we used APXS data of 62 sediment targets [3]. The normative mineral composition was calculated from APXS according to the CIPW procedure to calculate the estimated density of the material and to classify in QAPF system.

The analyses show five deposit classes: i) dust with very fine sand enriched in sulphur, ii) fine basaltic sand, iii) coarse sand enriched in iron, found only on the plains, iv) gravel enriched in iron, also found on the plains, and iv) gravel with a typical for basalts amount of iron, found at the Endeavour crater rim. These classes occur in the following geomorphological settings: i) dust mixed with very fine sand is common on the leeward side of topographical obstacles, ii) fine sand is present in depressions, iii) coarse sand is related to coarse-grained ripples fields, iv) gravel occur as a lag deposit, especially in coarse-grained ripple troughs and at crater rims and outcrops.

The typical diameter of grains for the fine sand is 0.13 mm, and for the coarse sand - 1.20 mm. The best sorted coarse sands were found on the slopes and the crests of coarse-grained ripples. In most cases, the normative mineral composition of deposits fits in the basalt/andesite field of the QAPF classification. The coarse sand found in coarse-grained ripples was characterized by the highest content of iron and shows the most mafic composition in the QAPF diagram. This deviation from the basalt composition is related to iron-rich spherules (a frequent component of the gravel) than to a more mafic type of rock. On the other hand, the coarse sand grains found in ripple fields were characterized by lower roundness than the iron-rich spherules. Therefore, many of the transported by wind coarse sand grains had their origin in partial fragmentation of iron-rich spherules.

The work was funded by the Anthropocene Priority Research Area budget under the program "Excellence Initiative – Research University" at the Jagiellonian University.

[1] Herkenhoff, K. E. (2003) MER1 Microscopic Imager Science Calibrated Data Bundle. PDS Geosciences Node. DOI: 10.17189/1519006

[2] Kozakiewicz, J. (2018). Image Analysis Algorithm for Detection and Measurement of Martian Sand Grains. Earth Science Informatics, 11, 257-272. DOI: 10.1007/s12145-018-0333-y

[3] Gellert, R. (2009). MER APXS Derived Oxide Data Bundle. PDS Geosciences (GEO) Node. DOI: 10.17189/1518973

How to cite: Kozakiewicz, J., Kania, M., Salata, D., and Nowak, L.: Sand properties investigation at Meridiani Planum, Mars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3863, https://doi.org/10.5194/egusphere-egu23-3863, 2023.

ExoMars is an astrobiology program led by the European Space Agency, which aims to launch a rover to Oxia Planum to search for signs of past life. Although the primary goal of the mission is focused on astrobiology, there are several secondary mission objectives, such as investigating the geomorphology, aeolian and volcanic processes to better understand the evolution and paleoclimate of Mars. CLUPI (a close-up imager) will be used to acquire high-resolution images of rocks, geological outcrops, and drill cores to provide the overview on the geology of Oxia Planum. Due to the limited amount of data that can be transmitted at once from Mars, only few CLUPI images will be available daily to the science team for assessing hypotheses and decide how to program the rover of the next cycle of activities. Thus, it is curial that each CLUPI image will contain a maximum of relevant information. For this reason, we are conducting preparatory tests and simulations to identify ideal CLUPI working conditions in view of the prime mission on Mars. In this work, we specifically explored the impact that different illumination conditions (i.e., direction of the illumination axis and intensity of direct light vs diffused light) may have on the detection of textures and sedimentary structures in close-up images. We showed that by acquiring images at different type of day, under specific lighting conditions, it is possible to enhance the probability of detecting various rock textures and geological samples, which can contribute to the diverse data collection and answer main question about the geomorphology of Oxia Planum.

How to cite: Kuhn, N. J., Ligeza, G., Bontognali, T., Josset, J.-L., and Kuhn, B.: Exploring biosignatures and geomorphology of Mars with close-up images – preparatory activities for the ExoMars mission., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10961, https://doi.org/10.5194/egusphere-egu23-10961, 2023.

This research deals with the detailed study of some global-scale geomorphological structures on Mars to identify possible current or fossil methane emission points. For years, attempts have been made to understand the mechanism that led to the formation of methane on Mars and how it may have been stored to date in subsurface reservoirs. From the data recently received from satellites (Tracer Gas Orbiter on board of ExoMars, Planetary Fourier Spectrometer on Mars Express) and rovers (Mars Science Laboratory Curiosity in Gale crater) on Mars, it is possible to infer that the methane on Mars is gradually emitted into the atmosphere and most of the times is detected by these instruments. Thanks to these dataset of methane emissions during the years (since 2004 with the PFS first detections) it is possible to trace the possible points in which the upper limit concentration of methane are equal to or greater than 10 p.b.b.v. so as to select a few areas where to begin the geomorphological and mineralogical analyses for this research in order to create a global map of possible areas where current methane emissions from subsurface methane reservoirs may be recorded. For this study the focus will be on hectometric to kilometric mounds of volcanic or sedimentary origin (mud volcanoes and/or pingos like structures), chaotic terrains and fracture fields in sedimentary piles. The areas selected for this research are Coprates and Candor Chasma (Valles Marineris, Mars), Nili Fossae (Mars), Vernal crater and the surrounding of Arabia Terra (Mars) and Gale crater (Mars). All of these locations have key characteristics such as proximity to a boundary zone (Gale crater), the presence of a fracture system (Nili Fossae), presence of mud volcanoes or pingoes (Valles Marineris and Utopia Planitia): all possible incentives for the presence of methane emission spots. The aim of this project, as already mentioned, will therefore be to analyse these areas in detail, trying to understand whether they could be or have been methane emission points, with the help of the planetary analogues that can be found in Azerbaijan regarding mud volcanoes, in Canada for pingos or fracture systems in China.

How to cite: Mariani, E. and Allemand, P.: Methane on Mars: Correlation of geomorphological features with current methane emissions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5338, https://doi.org/10.5194/egusphere-egu23-5338, 2023.

NASA's Solar System Treks Project (SSTP) online portals provide web-based suites of interactive visualization and analysis tools to enable planetary scientists, mission planners, students, and the general public to access mapped data products from past and current missions for a growing number of planetary bodies. 

The Solar System Treks portals provide advanced data visualization and analysis capabilities for data returned from a vast number of instruments aboard many past and current missions to a growing number of planetary bodies throughout Solar System. Multiple map projections as well as interactive 3D views are available to optimize visualization of different landforms. A detailed set of analysis tools helps users find and interpret morphological features across diverse landscapes on the surfaces of planets, moons, and asteroids. In some cases, these tools make use of machine learning and artificial intelligence to help users locate, identify, and understand landforms drawn from very large datasets. Having an integrated suite of portals presenting geomorphology across a range of planetary bodies within the Solar System greatly facilitates studies of comparative planetology. The portals are currently being used for site selection and analysis by NASA and its international and commercial partners supporting upcoming missions. 
Today, 11 web portals in the program are available to the public. This list includes portals for the Moon; the planets Mercury, Venus, and Mars; the asteroids Bennu, Ryugu, Vesta, and Ceres; and the outer moons Titan and Europa. The Icy Moons Trek portal features seven of Saturn’s smaller icy moons. All of the portals are unified under a project home site with supporting content. These web-based portals are free resources and publicly available. 

This presentation for EGU will detail and share examples of the how the portals can be applied to research in planetary geomorphology.

How to cite: Day, B. and Law, E.: Exploring Planetary Geomorphology with NASA’s Solar System Treks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3981, https://doi.org/10.5194/egusphere-egu23-3981, 2023.

Introduction: The WGCCRE has made recommendations regarding the lunar reference frame (LRF) [1]. Over the last 2 years both the Artemis III SDT report [2] and the LEAG-MAPSIT LCDP SAT report [3] have included recommendations for an updated lunar reference frame. Park et al. [4] have published new Solar System ephemeris results that include a new lunar laser ranging (LLR) solution and lunar orientation ephemerides. The latter includes the DE440 ephemeris in the Mean Earth/polar axis (ME) frame, which is compatible with their earlier DE421 ME frame recommended for use by the WGCCRE.

Given the recent activities and interest on the LRF, and the expected increase in lunar missions by the various nations, it is appropriate for the WGCCRE to consider updating the recommendations on a LRF. We are soliciting input on such a recommendation.

Issues to consider: The Moon is one of few bodies in the Solar System without a specific longitude defining feature. It may be timely to use an LLR solution to define the LRF, following long-standing IAU and WGCCRE recommendations [1, p. 7]. Currently, a particular such LLR solution is already the underlying basis for the DE421 ME frame. Such a solution and similar future improved solutions could instead serve to directly define the frame in the ME system, and in practice would match in a no-net rotation sense the existing recommended DE421 ME frame.

Separately, the lunar orientation model could now be specified by using the JPL DE440 ephemeris in the ME frame. The new JPL solutions use substantially more available data, and improved modeling compared to the previous (2008) DE421 solution. Differences from the previous model are less than 1 meter during the period 1900–2050. Differences in the underlying LLR solutions are < 1.5 meters. Such differences are not so significant as to be noticeable in the positioning of data products except at the highest current levels of accuracy. This update would nevertheless help to prepare for the best future accuracy by removing one source of error.

We will present the benefits of updating the LRF and weigh them against the burden of changing the established definition.

Request for input: The WGCCRE is requesting feedback from the lunar community on these issues. Is using (the current new JPL) LLR solution to define the LRF appropriate? Is using the DE440 ephemeris in the DE421 ME frame appropriate as a new lunar orientation model? Are there other LLR and lunar ephemeris solutions that could be considered for use in this process? Feedback to the lead author is welcome, preferably by the time of or at the EGU meeting. We hope to complete the next version of our main WGCCRE report this year and possibly include an update for a recommended LRF definition.

References: [1] Archinal et al. (2018) CMDA 130:22. [2] NASA (2020) NASA/SP-20205009602. [3] LEAG-MAPSIT Special Action Team (2021), see MAPSIT website. [4] Park et al. (2021) The JPL Planetary and Lunar Ephemerides DE440 and DE441, Astron. J. 161(3), 105.

How to cite: Archinal, B. and Working Group on Cartographic Coordinates and Rotational Elements, I. A. U.: Updating the Lunar Reference Frame, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9136, 2023.

Aeolian sand transport on Mars is active today and was likely so throughout its history. Widespread dune motion is theorized to comminute sand to sub-sand sizes, a process also implied by lab experiments. In view of this sand destruction, discovering the source(s) and origin(s) of Martian sand provides critical information for understanding Martian sediment cycling.

Local sand sources have been discovered and considered to be consistent with the long-standing hypothesis for Martian sand as volcaniclastic in origin. A local source of Martian sand has recently been inferred in the western Medusae Fossae Formation (wMFF). Given the pyroclastic origin of the vast MFF, the new discovery of sand generation from that deposit substantiates a volcaniclastic origin of Martian sand.

However, the wMFF is limited in extent and unlikely to constitute an origin for the globally distributed dune fields on Mars. Continued exploration for sand origins is needed to explain this widespread distribution.

We examined the five global geological units interpreted as volcaniclastic, which yielded limited evidence of sand sourcing outside the wMFF. In these five units, sand sourcing was detected in visible-wavelength data in the Hesperian and Amazonian transitional units that comprise the central and eastern MFF and in the Noachian units of Arabia Terra. Investigation to characterize sand production from these units is revealing a variety of sand source outcrops.

Tracing sand deposits back to their sources is another approach for determining sand origins, as was used in determining the source – and thereby the origin – of sand in and from the wMFF. Determining sources for the widespread sand on Mars requires determining sand survivability: how far could sand travel from their sources before being destroyed by comminution to sub sand sizes? Simulation of aeolian transport on Mars has shown different sand mineralogies comminuting at different rates, suggesting that the bulk mineralogy of a sediment may change with increased transport distance. Building on that previous experimental work, we are undertaking comminution of 14 different Mars-analog sands to more fully characterize the mineralogical and physical effects on sand of aeolian transport. The results will support using dune sand compositions and distances from possible source outcrops to test if these outcrops sourced the sand.

Thermal inertia is used to characterize Martian sand, e.g., to estimate grain sizes. Available dune field mapping facilitates investigation into dune sand thermal inertia values, thereby providing data, e.g., on sand particle sizes and induration states. As available mapping incorporates non-sand substrate, we are remapping dune fields to include only visible sand and using the distributions of thermal inertia values to assess if non-sand substrate is still included in our mapping. Having completed remapping of tropical dune fields, we are beginning analysis of their thermal inertia values. The results will reveal any trends relative to geography, underlying geologic unit, elevation, and other factors.

These three investigations – into the sources and origins, effects of transport, and thermal inertia values of Martian sand – will support improved understanding of Martian aeolian sand cycling, one of the most active geologic agents on Mars.

How to cite: Burr, D., Finch, J., Baker, A., Fry, R., Nguyen, V. N., and Chinchkhede, T.: How does sediment cycling work on Mars? Three investigations into the cycling of Martian aeolian sand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8692, https://doi.org/10.5194/egusphere-egu23-8692, 2023.

The contemporary surface of Mars is shaped by wind driven sand transport, yet our knowledge of these processes is limited. Sand ripples are small bedform features commonly found superimposing dunes on the surface of Earth and Mars, perpendicular to the local wind direction. The mechanism behind the formation of Mars’ ripples is currently highly debated: either they are formed by saltation like Earth’s aeolian impact ripples, or they are formed by hydrodynamic instability such as subaqueous ripples. Investigating ripple pattern dynamics across the surface of Mars would improve our knowledge of local wind regimes and sand transport conditions, such as whether the dune shape and size affect wind flow, thus ripple patterns.

To enable efficient surveying of large areas of the surface of Mars, an automated mapping method has been developed to identify and categorise different classes of ripple patterns. For this project, ripple patterns found on barchan dunes across 40 HiRISE sites in the north polar region of Mars have been classified and segmented. The same mapping method will be applied to Earth’s aeolian impact ripples and subaqueous ripples to compare their morphology and dynamics with those on Mars. By doing so, we hope to determine the mechanism behind the formation of Martian ripples and more broadly enhance our understanding of sand transport conditions on the red planet.

How to cite: Delobel, L., Baas, A., and Moffat, D.: Analysis of Dune Ripple Patterns on the Surface of Earth and Mars to determine Local Sand Transport Conditions: A Machine Learning application., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-392, https://doi.org/10.5194/egusphere-egu23-392, 2023.

How to cite: Bohaceck, E. V., Bahia, R. S., Braat, L., Boazman, S., Sefton-Nash, E., Orgel, C., Wilson, C., and Riu, L.: Modelling River - Dunes Interactions on Titan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2831, https://doi.org/10.5194/egusphere-egu23-2831, 2023.

During the martian year the surface temperatures in winter dip below the condensation temperature of carbon dioxide and it freezes onto the surface. In the spring, it sublimates directly back into the atmosphere and observations reveal that this cycle of condensation-sublimation results in identifiable sediment transport on the martian surface. We use data from the Colour and Stereo Surface Imaging System (CaSSIS) on ESA's Exomars Trace Gas Orbiter to illustrate the range of landforms thought to be created by these sublimation processes. Previous experiments have revealed that condensation of CO₂ ice into the regolith pore space and its subsequent sublimation can result in downslope sediment transport. they also showed that aeolian sand was less prone to sediment motion triggered by sublimation than martian regolith simulant and it was suggested the presence of dust could be responsible for this difference. As dust is an important component of the martian atmosphere and surface, in these experiments we explore the influence of dust content on the sediment transport processes and capacity for sediment transport.

Our experimental setup consists of a liquid nitrogen cooled copper sample holder ~30cm long by 20 cm wide within which the sediment is formed into a slope at 30° (max. depth 10 cm). This container is placed inside the Open University’s Mars Chamber which has has a length of 2 m and a diameter of 1 m. One experiment typically takes 2hrs, and the preparation takes 12-14hrs. First the chamber is evacuated and backfilled with CO₂ gas twice to purge terrestrial gases including H₂O. Once this is complete the sample holder is cooled with liquid nitrogen until all the sediment temperatures reach the condensation temperature of CO₂. The experiment then starts and a heat lamp is used to force the CO₂ sublimation.  The experiments are monitored by an array of cameras for photogrammetry, a high definition video camera to record the processes, pressure gauges to maintain/monitor the pressure and thermocouples to monitor the sediment and surface temperature.

In this series of experiments we vary the dust content in an aeolian sand matrix from 0 to 20% by weight by adding the clay fraction of the MSC simulant. We find no significant difference in the results between 0 and 5% dust content, then at higher values the transported volume and activity increases suddenly and the transported volume and activity remains stable at a higher level from 10% dust upwards. Our results reveal that a sediment transport threshold seems to exist between 5% and 10% dust content and therefore this factor must be considered when studying seasonally active surface processes on Mars.

How to cite: Conway, S., Beck, C., Herny, C., Cesar, C., Sizemore, H., Sylvest, M., and Patel, M.: The effects of dust content on surface sediment transport by carbon dioxide ice sublimation on Mars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3373, https://doi.org/10.5194/egusphere-egu23-3373, 2023.

            River deltas and fluvial fans are both fan-shaped landforms that contain complex channel networks. Fan shaped landforms have also been identified on Mars at Jezero, Eberswalde, and Gale craters among many other locations. A principal distinction between these two landforms is that only deltas systematically form along the shorelines of a standing body of water. Fluvial fans may form along a body of water, but can also form hundreds of kilometers inland. It is thus crucial to be able to accurately distinguish between deltas and fluvial fans for the purposes of mapping paleo-shorelines on planetary bodies and understanding paleoclimates. In this work, we apply multiple quantitative methods on Martian fan-shaped landform channel networks to map channel networks to differentiate fluvial fans from river deltas on Mars. We quantify differences in channel bifurcation and divergence angles due to channel crossovers. We also measure changes in channel reach length between bifurcation and divergence nodes. Differences in channel networks occur because fluvial fans are built by channel bed aggradation and channel avulsion. River deltas are constructed by both mouth bar growth and consequent channel bifurcations, as well as infrequent avulsions. In river deltas on Earth, channel bifurcations form at an angle of approximately 72°. Channel lengths and widths in river deltas decrease downstream with increases in successive channel bifurcations. On the contrary, fluvial fan avulsions generate smaller divergence angles and down-fan channel narrowing is not necessarily linked to divergence nodes. This project applies Earth derived channel network mapping techniques to Martian fan-shaped landforms and demonstrates that this methodology is applicable on Mars. Preliminary analysis of the channel network of the Jezero crater landform suggests that it resembles a fluvial fan and not a delta. Conversely, preliminary analysis of the Eberswalde crater channel network suggests that the landform here does resemble an Earth river delta. Our results indicate that fan-shaped channel networks can and must be carefully assessed. This is especially true if the presence of deltas is used for the estimation of the location of paleo-shorelines on planetary bodies, as only deltas regularly form at shorelines. Alternatively, additional evidence is required to identify paleo-shorelines as fluvial fans may also form along shorelines. On Earth, fluvial fans are less sensitive to sea-level rise and coastal hazards than deltas and thus react differently from deltas due to changing sea levels.

How to cite: Gezovich, L., Plink-Bjorklund, P., and Henry, J.: Quantifying the Channel Networks of Fan-Shaped Landforms on Mars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2928, https://doi.org/10.5194/egusphere-egu23-2928, 2023.

Eskers are sinuous sedimentary ridges formed in meltwater-filled subglacial tunnels. They are widespread in formerly glaciated landscapes on Earth. A small but growing number of late Amazonian-aged (~110-330 Ma) candidate eskers have been identified in Mars’ mid-latitudes in association with extant buried glaciers. These eskers are thought to have formed during periods when mid-latitude glaciation on Mars was more extensive than at present, due to variations in planetary spin-axis obliquity. The basal melting required for esker formation seems likely to have required elevated local or regional geothermal heating.

A recent study using current terrestrial theories for subglacial water flow adapted for Mars suggests that, if water was present beneath Martian ice masses, lower gravity favours the formation of efficient, tunnel-based drainage, as opposed to water flow through a distributed system of small cavities linked by water-filled orifices which is favoured for terrestrial ice masses. Tunnel-based drainage systems are more efficient, leading to lower water pressures and gradients, and slower water velocity.  Our previous experiments with a Mars-adapted model of esker sedimentation also suggest that, once a subglacial tunnel has formed, sediment deposition occurs more readily on Mars than Earth, as the lower gravity, and consequent lower water pressure and velocity, allows more rapid deposition.

These factors suggest that if subglacial water and mobilised sediment are present beneath Martian ice masses, esker formation is more likely on Mars than Earth as subglacial tunnels would be more widespread, and sediment deposition within them more rapid. However, this leads to questions regarding the likely source(s) of esker-forming sediment, and the water volumes needed to erode it. Initial calculations with a Mars-adapted model for erosion by subglacial water suggest that for a particle size typical of Martian sandy regolith (150 mm), erosion requires water velocities > 0.1 ms^-1. Calculated erosion rates vary from 5x10^-10 ms^-1 to 3.5x 10^-7 ms^-1 for water velocities between 0.1 ms^-1 and 1 ms^-1, and are higher than for equivalent terrestrial channels, largely because the critical shear stress needed to mobilise sediment is lower due to Mars’ gravity. This suggests that sediment will be readily mobilised beneath wet Martian ice masses, making the supply of water the critical limiting factor. Thus, this study will use an ice flow model to reconstruct a more extensive glacier over a candidate esker in the Phlegra Montes of Mars’ northern mid latitudes. Geothermal heat will be varied, along with other glaciological and climatic parameters, to investigate the possible extent of warm-based ice in the region, and to estimate the extent and volume of subglacial meltwater. The modelled meltwater will then be input into the Mars-adapted subglacial water erosion model to explore the impact of water availability and sediment characteristics on the possible extent of sediment erosion. Modelled sediment supply will then be compared with the sediment volume within the candidate esker, reconstructed from a 1 m/pixel digital elevation model, to help constrain the regional glaciological, sedimentological, climatological and geothermal conditions needed for esker formation.

How to cite: Arnold, N., Butcher, F., Gallagher, C., Balme, M., and Conway, S.: Estimating subglacial water discharges needed to form Amazonian-aged mid-latitude eskers on Mars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14816, https://doi.org/10.5194/egusphere-egu23-14816, 2023.

Defining criteria for mapping material units on airless, rocky bodies is challenging. Where the primary geologic process for most of a body’s history is impact cratering, traditional morphology-based mapping approaches may fail, because differences in morphologic characteristics among the various cratered surfaces can be hard to discern, and surface morphology is muted by the regolith’s physical and mechanical properties. In constructing a global geologic map of Vesta at 1:300,000-scale using the Dawn Framing Camera (FC), DTM-derived slope and contour, and multispectral data, we have countered this problem by utilizing a hybrid method of mapping that first requires creating two maps independently. The first map depends on morphology and topography to define map units, while the second uses spectral data to define units. The unique results of each map are then combined into the hybrid map units. 

Multispectral data provide unique insight into stratigraphy (material brought up through cratering processes) that is easily lost when using an albedo mosaic as the basemap. However, solely using a “color” ratio mosaic as a basemap easily magnifies potentially misleading data, because spectroscopy in the shorter wavelengths (UV-VIS-near IR) can only sample the upper few µm of the surface, and very little unique material is required to affect the signal of a regolith. Contacts defined by multispectral data may not coincide with clear morphologic boundaries as a result, so caution must be used in how the two maps are merged and clear criteria should be established to define hybrid map units.

We found that the crucial exercise in ensuring unique data were retained when combining these two maps was to create a decision tree for determining which data would be primary in choosing where to draw unit boundaries. We divided the decision tree into the following if-then statements:

• If saturated colors (meaning the color signal in color-ratio spectral data was strong and the color itself was easy to describe) matched unit boundaries derived from morphology, there was no conflict. For example, saturated colors on Vesta tend to be associated with fresher expressions or exposures of regolith, which are more likely found at the youngest, freshest craters/ejecta, easily demarcated morphologically.
• If muted colors exist, where the morphology is relatively clear, the morphology is the primary guide for unit definition, as it retains the least altered record of geologic processes and the most reliable record of the nature of the rock bodies. Colors provide additional characteristics of such units, allowing for some interpretation of composition.
• If saturated colors are not associated with morphologic boundaries, the color boundaries are interpreted to record the most recent (even if very thin) impact evidence. In such cases we have mapped the saturated color data as impact material. This preserves the underlying morphology/topography information while supporting stratigraphic interpretations based on excavated subsurface layers revealed by crater ejecta.
• In the case of muted colors where the morphology is unclear, decisions must be made case-by-case, using all available data to make a reasonable determination of where to mark unit boundaries.

How to cite: Yingst, R. A., Mest, S. C., Garry, W. B., Williams, D., Berman, D., and Gregg, T. K. P.: Mapping Vesta using a hybrid method for incorporating spectroscopic and morphologic data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8552, https://doi.org/10.5194/egusphere-egu23-8552, 2023.