The JUpiter ICy moons Explorer (JUICE) performed end of August 2024 its Lunar-Earth gravity assist consisting of a flyby of the Moon followed by an Earth flyby. During this manoeuvre the Particle Environment Package (PEP) was operated to investigate both the near lunar and the magnetospheric environment and to validate its performance. PEP consists of six individual sensors detecting ions, electrons and ENAs depending on their energy, arrival direction and mass. Here we focus on measurements of one of these sensors, the Jovian plasma Dynamics and Composition analyzer (JDC). JDC measures angular and mass-resolved positive and negative ions as well as electrons in an energy range from a few eV/q up to 35 keV/q. The JDC field of view covers a hemisphere and is divided into 16 x 12 angular pixels.

We present JDC data from the lunar flyby. During the flyby, the Moon was in Earth’s magnetotail. JUICE approached the moon from the side of the lunar wake. JDC was operated for ~103 minutes during the flyby with the exception of an 8 minutes long period around the closest approach to the Moon. The observed plasma densities during the lunar flyby were extremely low - making this region one of the emptiest spaces. Nevertheless, after entering the lunar optical shadow until the end of the measurement interval a weak signal at ~1.5 keV/q was detected. This signal is not an instrument background and is not visible before entering the Lunar optical shadow. We show ray tracing results to investigate the possible origin of these particles.

How to cite: Wittmann, P., Wieser, M., Barabash, S., Stenberg Wieser, G., Maynadié, T., Krupp, N., Roussos, E., Fränz, M., Brandt, P., Wurz, P., Halekas, J., and Poppe, A. and the PEP Team: Visiting the emptiest space – Analysing the JUICE Lunar flyby PEP-JDC data , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16581, https://doi.org/10.5194/egusphere-egu25-16581, 2025.

To date, plasma observations on the lunar surface have been very limited. Most of these observations were conducted during the Apollo program, relying on technology that is now over 50 years old, or by a few individual sensors with narrowly defined scientific objectives on Chinese landers. Our knowledge of the plasma environment and the processes that govern it remains sparse, relying heavily on orbital measurements and theoretical models. This current level of understanding is insufficient to support the large-scale exploration efforts that are about to commence. In essence, we are navigating a "Terra Incognita" in this domain.

To characterize and understand near-surface plasma and its interactions with the lunar surface are required for:

• Properly modeling surface and man-made object charging and potentials;
• Investigating dust dynamics, including dust release and dust-plasma interactions;
• Studying weathering processes that modify surface characteristics and compositions;
• Establishing the role of the space environment in the formation, release, and dynamics of volatiles within the lunar exosphere;
• Understanding plasma dynamics at the surface and interactions with various plasma domains as the Moon moves along the orbit.

Plasma and its interaction processes need to be studied across four fundamental scales:

• Microscale (kinetic, 10^-4 – 10^-2 cm) to address microphysics of the particle – surface interaction
• Mesoscale (sub-Debye, 10 cm–10 m) to investigate plasma process when quasi-neutrality breaks creating strong electric fields
• Macroscale (MHD, 10 m–1 km) to explore connections between plasma dynamics and topography
• Global scale (MHD, 1 km–1,000 km) to reveal effects of large-scale structures, such as magnetic anomalies and the terminator, on local plasma populations.

In this presentation, we demonstrate the limitations of our current knowledge, highlight the critical importance of advancing it, and outline steps to explore the "Terra Incognita" of plasma on the lunar surface.

How to cite: Barabash, S., Futaana, Y., Wittmann, P., Maynadié, T., Whizin, A., and Pontoni, A.: Plasma on the lunar surface: Terra Incognita to be explored, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13945, https://doi.org/10.5194/egusphere-egu25-13945, 2025.

Despite lacking a global magnetic field, the Moon features localized magnetized regions called lunar magnetic anomalies [1]. Their interaction with the solar wind results in significant proton reflection and deflection [2], creating unique structures often referred to as lunar mini-magnetospheres [3, 4]. Previous studies have shown that the largest magnetic anomaly, the South Pole-Aitken (SPA) cluster, induces global-scale perturbations in the near-surface lunar plasma environment on both the dayside [5, 6] and nightside [7]. However, its influence on the plasma environment in south polar regions remains unknown.

In this study, we produce new composite images of backscattered energetic neutral hydrogen derived from Sub-KeV Atom Reflecting Analyzer (SARA) [8] data. These images reveal that plasma perturbations generated by the SPA cluster can extend to lunar south-polar regions, depending on local time and upstream solar wind conditions. These perturbations affect solar wind proton precipitation patterns, either decreasing or enhancing impinging proton fluxes depending on whether the south pole lies downstream or outside of the SPA anomaly. Based on these observations, we develop an empirical model of solar wind compression by the SPA cluster to evaluate its impact on ion instrument measurements at the south pole.

Understanding the complex interactions between the plasma, dust, and electromagnetic environments is an important asset to ensure safe and sustainable human presence on the Moon. We will discuss the role of the SPA cluster in these interactions, which will establish preliminary measurement requirements for in-situ plasma instruments in polar regions.

References:

[1] Coleman et al. (1972), Physics of the Earth and Planetary Interiors, https://doi.org/10.1016/0031-9201(72)90050-7.

[2] Lue et al. (2011), Geophysical Research Letters, https://doi.org/10.1029/2010GL046215.

[3] Lin et al. (1998), Science, https://doi.org/10.1126/science.281.5382.1480.

[4] Wieser et al. (2010), Geophysical Research Letters, https://doi.org/10.1029/2009GL041721.

[5] Fatemi et al. (2014), Journal of Geophysical Research: Space Physics, https://doi.org/10.1002/2014JA019900.

[6] Maynadié et al. (2024), Europlanet Science Congress 2024, Berlin, https://doi.org/10.5194/epsc2024-79.

[7] Dhanya et al. (2018), Geophysical Research Letters, https://doi.org/10.1029/2018GL079330.

[8] Barabash et al. (2009), Current Science, http://www.jstor.org/stable/24105464.

How to cite: Maynadié, T., Futaana, Y., Barabash, S., Bhardwaj, A., Wurz, P., and Asamura, K.: Effects of the South Pole-Aitken Magnetic Anomaly Cluster on the Plasma Environment at the Lunar South Pole, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4290, https://doi.org/10.5194/egusphere-egu25-4290, 2025.

The lunar crust has preserved a record of the Moon’s volcanic and magmatic activity through time. While the extrusive maria dominate the volcanic record, little is known regarding their thickness and the details of their emplacement. Intrusive activity is even more elusive, with most intrusions expressing little to no surface signature. Here, we present a global investigation and a volumetric inventory of extrusive and intrusive volcanic materials (Broquet & Andrews-Hanna, 2024a, 2024b). Gravity and topography are inverted using a two-layer loading model under the premise of pre-mare isostasy to constrain mare and cryptomare thickness, as well as updated crustal thickness models. Substantial lateral variations in mare thickness are found, with averages 7.9 km within large mare basins compared to 1.6 km outside of these basins. This important thickness variation associated with minimal change in the surface topography can be explained by some combination of long-distance transport of low viscosity mare and/or a buoyancy control limiting mare eruptions to a constant level surface.

Our inversion predicts the shape of the lunar crust before it got obscured by mare materials. The pre-mare surface of the nearside Oceanus Procellarum region is ~2 km lower than the surroundings, and possible explanations, including a giant impact, pore space annealing, isostatic adjustment, and plume-induced crustal erosion, are discussed. The western part of Imbrium’s ring is not found in the pre-mare topography, implying that it never formed or that some processes erased its signature from gravity and topography. The feldspathic, pre-mare, crust is ~7 km thinner within large nearside basins than in models not accounting for the high-density mare. The pre-fill floor of these basins was ~6 km deeper than currently observed. These new insights have implications for impact simulations that try to reproduce the crustal structure of nearside mare basins.

Our preferred volumes of mare and cryptomare total to 20×10⁶ km³. Investigation of crustal intrusions associated with linear gravity anomalies, floor-fractured craters, ring dikes, graben, and beneath volcanic constructs, yield a total volume of 9×10⁶ km³. The major fraction of intrusive materials is in the form of ring dikes located at the margin of large basins in zones of flexural extension, which indicates an important control of lithospheric stress on magma ascent. Taken together, the total volume of the secondary crust corresponds to ~2% (and up to 5%), of the total lunar crust volume. The combined volume of intrusives and extrusives is found to be 3 times greater in the nearside than in the farside. Intrusive activity dominates in the farside (intrusive:extrusive ratio of 5:2), whereas extrusive volcanism is more pronounced in the nearside (1:5). Both are related to the lunar asymmetry in which the thinner crust and warmer subsurface beneath the Procellarum KREEP terrane enables enhanced melting and magma ascent. The strong asymmetry in melt production supports an early KREEP migration, which must have been established 100 s of Myr before nearside volcanism began to allow for the buildup of heat.

Broquet, A., & Andrews-Hanna, J.C. (2024a). Icarus 408. 10.1016/j.icarus.2023.115846.

Broquet, A., & Andrews-Hanna, J.C. (2024b). Icarus 411. 10.1016/j.icarus.2024.115954.

How to cite: Broquet, A., Andrews-Hanna, J. C., and Plesa, A.-C.: Lunar volcanism: A Geophysical perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15674, https://doi.org/10.5194/egusphere-egu25-15674, 2025.

The predominant concentration of volcanic activity and surface enrichment of heat producing elements (HPE) on the lunar nearside suggest an asymmetry in interior properties and thermal history of the Moon. The distribution of HPE beneath the surface and the processes that led to their enrichment on the nearside surface remain poorly understood (Gaffney et al., 2023). Interior radiogenic heating directly affects surface heat fluxes measured in situ during the Apollo program (Langseth et al., 1976), and estimated from orbit at the Compton-Belkovich (Siegler et al., 2023) and Region 5 locations (Paige & Siegler, 2016). 

Here, we link the subsurface distribution of HPE to the present-day surface heat flux using 3D thermal evolution models. We investigate the interior dynamics of the Moon from the post magma ocean crystallization phase to present-day using the mantle convection code GAIA (Hüttig et al., 2013). Similar to Plesa et al. (2016), we use a spatially variable crustal thickness model as input (Broquet & Andrews-Hanna, 2024). We investigate the structure of a putative HPE-rich layer underneath the PKT (Procellarum KREEP Terrane, Jolliff et al., 2000) assuming a circular geometry. We vary its location, size, depth and HPE enrichment compared to the mantle and anorthositic crust. Our models consider the HPE concentrations as constrained from magma ocean crystallization studies, but assume that additional mechanisms may have led to a migration of heat sources below the PKT region. 

Similar to Laneuville et al. (2013), we find that an enriched layer placed below the crust can efficiently heat up the mantle and contribute to explaining prolonged lunar magmatism. We show that the prominent gravity anomaly associated with the warm mantle beneath the PKT (Laneuville et al., 2013; Grimm, 2013) can be used to construct updated crustal thickness models, which display a substantially thinner nearside crust.

Our models show that a large HPE anomaly underneath PKT (~1500 km radius) allows sufficient surface heat flux variability to account for the low Region 5 value (Paige & Siegler, 2016) and the Apollo 15 & 17 measurements (Langseth et al., 1976). Conversely, a smaller anomaly (<1200 km) fails to produce any significant difference in surface heat flux between Apollo 17 measurement and Region 5 estimate. However, this geometry may help explain the absence of Imbrium’s western ring (Broquet & Andrews-Hanna, 2024) and the spatial variability in the relaxation state of lunar basins (Ding & Zhu, 2022).

Our models provide an important baseline for the interpretation of upcoming heat flux measurements within Mare Crisium (TO19D, Nagihara et al., 2023) and Schrödinger Crater (CP-12, Nagihara et al., 2023), predicting that the heat flux at Crisium and Schrödinger should be comparable to that measured at Apollo 17 and estimated at Region 5, respectively. Significantly different heat flux measurements would have profound implications for our understanding of the distribution of radiogenic elements within the lunar interior. Lastly, quantifying the subsurface thermal state and the distribution of HPE on the Moon will prove crucial for infrastructure development in the framework of the Artemis program. 

How to cite: Santangelo, S., Plesa, A.-C., Broquet, A., Breuer, D., and Root, B. C.: Constraining the distribution of radiogenics on the Moon from global geodynamic models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-566, https://doi.org/10.5194/egusphere-egu25-566, 2025.

Apollo lunar seismic data are essential for understanding the Moon’s internal structure and geological history. Despite being collected over five decades ago, the Apollo dataset remains the only available source of lunar seismic data, continuing to provide valuable insights into the interior of the Moon and its seismic activity. Recent advances in artificial intelligence, particularly deep learning techniques, have significantly enhanced planetary seismology by providing novel and powerful methods for analyzing previously under-explored, or even unrecognized seismic signal types. In this study, we apply deep learning for unsupervised clustering of lunar seismograms, revealing a new kind of long-period seismic signal that persisted every lunar night from 1969 to 1976. Through a detailed analysis of its timing, frequency, polarization, and temporal distribution, we concluded that this signal is likely induced by the cyclic heater, rather than being an artifact of voltage changes or other artificial sources. In addition to this newly identified signal, the unsupervised clustering algorithm also revealed a class of step/spike signals in acceleration (ACC-Step/Spike) similar to calibration signals. We built a comprehensive search of these signals using template matching, and then analyzed their features. These signals are particularly prevalent during lunar sunrise, sunset, and noon, and their amplitude range varies with temperature as well. Unlike the calibration signals with linear polarization, these ACC-Step/Spike signals exhibit elliptical polarization. Their incidence angles occasionally show noticeable variation during sunrise and sunset. Their characteristics in terms of azimuth and incidence angles also exhibit significant differences between the vertical and horizontal components. For example, in the horizontal component, the azimuth distribution is relatively uniform, and the incidence angle is nearly vertical. In contrast, in the vertical component, the azimuth distribution is sometimes more stable, and the incidence angle distribution is more uniform. Furthermore, our clustering results uncovered short-period abnormal signals near lunar noon and those caused by instrument malfunctions. Our research introduces a novel method for discovering new types of planetary seismic signals and enhances our understanding of Apollo seismic data. The discovery of long-period signals and the ACC-Step/Spike catalogs provide valuable references for future lunar seismic observations and data interpretation, thereby benefiting the analysis of lunar seismic signals.

How to cite: Liu, X. and Li, J.: Searching for Under-Explored Signals in Apollo Seismic Data by Deep Learning and Template Matching, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9482, https://doi.org/10.5194/egusphere-egu25-9482, 2025.

Crater chronology models rely on correlating observed crater size-frequency distributions (CSFDs) on the ejecta blankets of Copernican-age craters with cosmic-ray exposure ages of samples acquired by Apollo missions. However, these crater populations are known to vary on the ejecta of these craters. One explanation is that impact melts, boulders, and other variations in material properties can influence the scaling of impact craters. We conduct crater counts on the ejecta of several Copernican-age craters and find that crater densities vary with the thermophysical properties of the ejecta as observed by the Lunar Reconnaissance Orbiter Diviner instrument, providing evidence that the strength of ejecta materials can have a significant influence on CSFDs. Specifically, we find that as Diviner-derived rock abundance increases, the spatial density of craters decrease. Absolute model ages are affected as areas of higher rock abundance yield younger ages. This suggests terrain properties should be taken into consideration when deriving absolute model ages.

How to cite: Williams, J.-P., Pathare, A., and Costello, E.: Variations in Lunar Crater Populations Due to Target Properties, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20532, https://doi.org/10.5194/egusphere-egu25-20532, 2025.

High-speed impacts are the most fundamental of the currently known geological process in the Solar System. Luna preserves a comprehensive record of impacts since its formation 4.53 billion years age (Ga). Particles of silicate glass formed by impact melting may have recorded the timing of the impact event and reflected the composition of crustal target materials. Previous studies have used ³⁹Ar-⁴⁰Ar and U-Pb chronometric systems to date lunar impact glasses, while their source characteristics were assessed using major and trace element data. The return of the Chang'e 5 sample provides an opportunity for a more comprehensive analysis of lunar impact history by comparing the ages of impact glasses from different locations.

In this study, we collected approximately 800 sets of isotopic age data and corresponding major and trace element data for impact glasses, primarily from samples returned from the Apollo series of missions and the recent Chang’e 5 mission. Impact glasses for which no age data could be obtained were removed. Impact flux curves were generated by normalizing the estimated age data. Sampling points on the lunar nearside show three distinct curve patterns. The impact flux curves of Chang'e 5 and Apollo 12 exhibit a common, prominent impact interval during the lunar Copernicus Period. The impact flux curves based on the Apollo 17 samples show only one prominent impact interval, namely the Late Heavy Bombardment (LHB) Event period (3.8-4.1 Ga). The intermediate region samples (Apollo 14, 15,16) exhibit both of these common, prominent impact intervals. These three impact flux curve patterns may be related to the geographic distribution of the sampling sites. To validate this potential relationship, we utilized a global catalog of lunar impact craters containing over 1.3 million craters to analyze the distribution of craters of similar diameter in contemporary regions. Preliminary results indicate that there are differences in the distribution of impact craters across different regions within the same geological period. These differences may be related to the Moon's rotation and orbital characteristics. 

How to cite: zhao, S. and fan, J.: Geospatial analysis of lunar impacts craters: a meta-analysis of impact glasses from all Apollo and Chang'e 5 missions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7589, https://doi.org/10.5194/egusphere-egu25-7589, 2025.

The nature of the sources and processes involved in the formation of Lunar High-Al and High-Ti basalts are not completely understood. Through petrological experiments designed to study the effects of inefficient plagioclase flotation during late-stage Lunar Magma Ocean (LMO) crystallization, we were able to find a possible mechanism for the Al and Ti enrichment for both types of basalts. Retained plagioclase in late-stage ilmenite-bearing cumulates (IBCs) within the lunar mantle results in low-fraction (1-10%) partial melts that are highly enriched in Al and have a high affinity with the composition of Apollo 14 and Luna 16 high-Al basalts. Additionally, melting of Ti-rich phases ilmenite and ülvospinel, is prominent at higher partial melting fractions (20-60%) resulting in melts that can be enriched in over 20% TiO₂, with high affinity to high-Ti basalts and picritic glasses.

These results imply that both types of magmas may share the same mantle source but formed at different stages of fractional melting processes. The ages of both basalt types may be related to this fractional melting process, with high-Al basalts known to be the oldest Lunar volcanism and youngest known samples, overlapping with the oldest ages for high-Ti basalts at ~3.8 Ga. Our findings can explain multiple aspects of the major element composition of these basalts, but there are other aspects that need to be accounted for. The higher-than-expected Mg contents in both types of basalts, and the presence of olivine and orthopyroxene in the multiple saturation points of high-Ti basalts despite the absence of these minerals in IBCs, indicate that additional processes are involved in the formation of these basalts or even in the formation of mantle cumulates.

The inefficient flotation of plagioclase during LMO crystallization has been proposed as a possible explanation for the lower thickness of the lunar crust compared to experimental determinations [1]. Our findings provide further evidence that flotation inefficiency is a possibility, and its consequences may go beyond crustal thicknesses, but may also affect posterior mantle dynamics and the composition of lunar volcanism.

[1] Charlier, B. et al. (2018), Geochim. Cosmochim. Acta. 234, 50-69.

How to cite: Astudillo Manosalva, D. and Elardo, S. M.: Inefficient plagioclase segregation during Lunar Magma Ocean Crystallization can link the mantle sources for High-Alumina and High-Titanium basalts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19115, https://doi.org/10.5194/egusphere-egu25-19115, 2025.

Selene’s Explorer for Roughness, Regolith, Resources, Neutrons and Elements (SER3NE) is a small satellite mission performing gamma-ray and neutron spectroscopy (University of Oslo), near-infrared spectroscopy (Royal Observatory of Belgium and Royal Belgian Institute for Space Aeronomy) , and laser altimetry, roughness, and albedo observations (Institute for Planetary Reserch - DLR) at unprecedented spectral and ground resolution. The aim is to characterize the lunar surface to unravel its volatile origin and delivery processes, to uncover the geological processes that shaped the Moon, to prospect lunar resources for ISRU at future landing sites, to determine the exact neutron lifetime and the orbital evolution of the Earth-Moon system.
The instruments will be carried by the modular, single-failure tolerant TUBiX20 satellite platform (Technical University of Berlin). To ensure the desired global coverage and resolution for all instruments the satellite will orbit the Moon on a eccentric polar orbit with a slowly, naturally drifting argument of perilune over the mission lifetime of one year. This mission concept is a pre-Phase A Study led by University of Oslo under an ESA contract.

How to cite: Werner, S. C. and the The SER3NE Team: SER3NE - A small orbiter mission to the Moon, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8239, https://doi.org/10.5194/egusphere-egu25-8239, 2025.

    Planetary seismic data are essential for studying planetary interiors and dynamics, yet acquiring high-quality recordings in harsh extraterrestrial environments turns out to be far more challenging than on Earth. In both the Apollo Passive Seismic Experiment on the Moon and the Seismic Experiment for Interior Structure (SEIS) on Mars, considerable transient disturbances—often referred to as “glitches”—span a wide range of frequencies, complicating the search for potential low-frequency signals of planetary free oscillations and gravitational wave responses. To address this issue, we propose an automated workflow for detecting and removing strong transient disturbances in Apollo seismic data with deep learning, thereby enhancing the recovery of weak long-period signals. We also examined two approaches for removing disturbance: (1) directly muting transient segments and applying Fourier transforms, and (2) treating these segments as data gaps and applying the Lomb–Scargle periodogram to uncover weak low-frequency signals. Synthetic tests show that even with ~80% of the data contaminated, most low-frequency peaks can still be recovered. Moreover, our workflow recovers the recently discovered temperature-related long-period signals in Apollo data without relying on stacking or clustering techniques, highlighting its vast potential in revisiting low-frequency components of Apollo seismic data.

    Complementing this disturbance-mitigation framework, we also evaluate the phasor walkout method, which determines whether a spectral peak originates from a true signal or merely from noise. The core assumption of this method is that harmonic signals will generate linear walkout patterns at their true frequency peaks, while random noise will produce irregular, random walkout paths. However, our findings indicate that random noise can contain a considerable amount of frequency peaks with deceptively linear phasor walkout patterns. Although noise in planetary seismic data are not random Gaussian noise, and artifacts observed in simple random noise may or may not arise in actual lunar or Martian data, this finding nonetheless highlights the need for extra caution when interpreting phasor walkout results in planetary seismic data.

    In summary, our study offers both an effective strategy for strong-disturbance removal—enabling the search for weak low-frequency signals—and an assessment of the phasor walkout method, raising awareness of risks in potential misinterpretations. These insights not only open new avenues for re-examining legacy Apollo data but also provide gentle reference in detecting planetary free oscillations and other low-frequency seismic signals.

How to cite: Xiao, Z. and Li, J.: Apollo Lunar Seismic Data Disturbance Mitigation and Phasor Walkout Method Assessment for Searching Planetary Free Oscillations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8502, https://doi.org/10.5194/egusphere-egu25-8502, 2025.

Mass wasting events on the Moon have been documented since the Apollo era and are distributed across its surface. On Earth, the morphology and runout distance of landslides, particularly flowlike landslides such as debris and mud flows, are strongly influenced by the mobilized soil and bedrock properties, notably the water content.

Despite the absence of widespread, liquid surface water on the Moon, previous surveys identified numerous lunar flow events across the Moon’s equatorial regions (± 60° latitude), termed “granular flows” or “flows”, in short, excluding the polar regions due to unfavorable illumination conditions. The recent release of ShadowCam images now enables the extension of past mapping efforts to the shadowed portions of the lunar polar regions (> 80° latitude).

Here, we perform a thorough, manual search for flows in polar region craters using images from the Korean Pathfinder Lunar Obiter (KPLO) ShadowCam and the Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC). We analyzed three regions for comparison: the Equatorial Region (Eq) (±60°), the South Pole Region (Sp) (80°–90° S), and the North Polar Region (Np) (80°–90° N). We focused our mapping efforts on flows in craters where more than 1% of the internal area has slope angles exceeding 30°. We utilized 131 ShadowCam images and 84 processed NAC images to map flows. Additionally, 100 random highland events from the Eq region were manually mapped for comparison with polar events.

We identified 23 Sp and 99 Np flows, distributed across 3 and 16 craters, respectively. A significant disparity emerged between the Eq and polar regions. While 38.7% of craters with slopes exceeding 30° in the Eq region contained flows, the percentages dropped to 33.3% in Np and 16.6% in Sp. Consequently, the likelihood of developing flows in Np and Sp with the same distribution as the Eq region is only 8.02% and 0.59%, respectively. Notably, Sp flows occur in areas with relatively lower LPNS-derived Water Equivalent Hydrogen (WEH) and outside permanently shadowed regions (PSRs) compared to Np flows. We observe no significant differences in geomorphic flow characteristics between the three regions. Flow efficiency (flow height/length, or H/L) averaged ~0.6, and the median source angle was ~32° across all regions.

Our results suggest that flows are 1) scarce in the polar regions, yet 2) do not exhibit anomalous geomorphologic properties in comparison to equatorial (dry) flows. This suggests the presence of an inhibitory factor - or the absence of the pre-conditions required for flow formation. Ongoing work is investigating whether our observations could be explained by a cementing effect caused by (near-)surface volatiles. The accumulation of volatiles might strengthen the regolith, reducing the probability of flow initiation due to meteorite-induced seismicity or moonquakes. Our observations might also indicate that potentially large quantities of subsurface volatiles are not shallow enough to cause and/or become mobilized in flow events. It is also possible that the observed flows formed before volatiles accumulated.

How to cite: Pedrelli, R., Bickel, V., Aaron, J., and Deutsch, A.: Volatile Ice Presence Analysis through Mass Wasting Events Mapping in Lunar Permanently Shadowed Regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6664, https://doi.org/10.5194/egusphere-egu25-6664, 2025.

Although metallic iron (Fe⁰) is a ubiquitous product of space weathering, its formation mechanisms are still poorly understood. On the lunar surface, Fe⁰ particles ranges in size from a few nm to several mm and are widely believed to have formed by a variety of mechanisms. These include the in-situ reduction of FeO during cosmic ray bombardment, localized heating by micrometeorites and the subsequent reduction of FeO, as well as the addition of Fe⁰ from iron-nickel meteorites during micrometeorite bombardment (Hapke, 2001; Kuhlman et al., 2015; Gopon et al., 2017; Day, 2020). The exact formation mechanism has wide ranging implications for remote spectral analysis of airless planetary bodies, the cosmic ray and micrometeorite flux to the Moon, correction of bulk-geochemical data on the moon, and the potential of the lunar surface to be a source of critical metals.

We present the results of a combined Electron Probe Micro-Analyses (EPMA) and Atom Probe Tomographic (APT) study to characterize the composition of Fe⁰ from Apollo 16 Regolith (sample #61500). Combining these techniques allowed us to explore the wide range of textural occurrences and size fractions of Fe⁰ and constrain the origin and emplacement mechanisms of these metallic regolith components. We focused on the germanium, iron, and nickel concentrations of the Fe⁰, as these three elements are key tracers that enable differentiation of in-situ vs extra-lunar processes. Our work shows that all Fe⁰ analysed in sample 61500 exhibit a meteoritic geochemical signature, which is most closely linked to the IIAB group of iron meteorites  (Gopon et al., 2024). This rare meteorite group is notable for its low nickel but high germanium concentrations. The lunar regolith’s significant inventory of meteoritic metals implies that it is a potentially valuable resource for a range of critical metals (EU Report, 2023), not least the Pt group metals and germanium. Furthermore, the host phase – npFe –contained within powdered regolith implies extraction and refining of these elements might be significantly more energy and cost effective than terrestrial deposits.

References:

Day, J.M.D., 2020, Metal grains in lunar rocks as indicators of igneous and impact processes: Meteoritics and Planetary Science, v. 15, doi:10.1111/maps.13544.

EU Report, 2023, Study on the Critical Raw Materials for the EU 2023 – Final Report:

Gopon, P., Douglas, J.O., Gardner, H., Moody, M.P., Wood, B., Halliday, A.N., and Wade, J., 2024, Metal impact and vaporization on the Moon’s surface: Nano-geochemical insights into the source of lunar metals: Meteoritics & Planetary Science, v. 59, p. 1775–1789, doi:10.1111/maps.14184.

Gopon, P., Spicuzza, M.J., Kelly, T.F., Reinhard, D., Prosa, T.J., and Fournelle, J., 2017, Ultra-reduced phases in Apollo 16 regolith: Combined field emission electron probe microanalysis and atom probe tomography of submicron Fe-Si grains in Apollo 16 sample 61500: Meteoritics & Planetary Science, v. 22, p. 1–22, doi:10.1111/maps.12899.

Hapke, B., 2001, Space Weathering from Mercury to the asteroid belt: Journal of Geophysical Research, v. 106, p. 39–73.

Kuhlman, K.R., Sridharan, K., and Kvit, A., 2015, Simulation of solar wind space weathering in orthopyroxene: Planetary and Space Science, p. 1–5, doi:10.1016/j.pss.2015.04.003.

How to cite: Gopon, P., Douglas, J., Moody, M., Halliday, A., Wood, B., and Wade, J.: Nano-geochemical insights into the source of lunar metals, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4338, https://doi.org/10.5194/egusphere-egu25-4338, 2025.

Imaging Infra-Red Spectrometer (IIRS), sent on-board Chandrayaan-2, has been mapping the lunar surface since 2019 with high spatial (80 m/pixel) as well as spectral resolutions (0.7 to 5 µm) [1-3]. This study uses two IIRS images, portions of which encompass the floor of Schrödinger Basin. Surface temperatures were derived from the two overlapping IIRS strips, which were then used to study the thermal properties of a part of the basin’s floor. Additionally, surface temperatures were also acquired by processing corresponding Diviner data, by matching IIRS pixels according to their Ground Control Points (GCPs) along with their local times of acquisition. It has been deduced that, for a particular period of time, the temperatures derived from IIRS are comparable with the corresponding Diviner data. Furthermore, factors contributing towards the mean temperature differences between the IIRS and Diviner datasets have been identified.

In order to use the temperatures obtained from IIRS, a case study on the ~320-km-wide-Schrödinger Basin was performed. In this regard, a volcanic vent (Schrödinger G), situated at 75° S and 139° E was studied, which is known to have deposited pyroclastic material on the basin floor [4-5]. Our analysis on the pyroclastic material-covered surface around the vent reveals several interesting findings: (1) Using the temperature data from IIRS, we were able to identify two distinct morphological units within the same pyroclastic deposit. The two units surrounding the vent exhibit different surface temperatures (an average relative difference of ~25-30K). (2) We have also used Clementine UVVIS colour-ratio data to identify differences related to soil mineralogy across the two deposits. The two units display contrasting tonal signatures on the UVVIS FCC image, thereby confirming the presence of two mineralogically distinct surface units. (3) In addition, using images from LRO-NAC, we have also performed a crater size frequency distribution (CSFD) measurement on the two units to estimate their relative ages. Our analysis reveals that the vent has experienced multiple eruptions, with the oldest ~3.7 Ga ago, while the latest being ~1.8 Ga ago, interspersed with different eruptions in between. Furthermore, CSFD measurements reveal that one of the units is significantly younger than the other. Based on the above results, we attribute the deposition of materials with different textures on either side of the vent to the several episodes of eruptions.

In conclusion, due to IIRS’s relatively higher spatial resolution, it was possible to identify and establish significant differences within a single pyroclastic deposit on the basis of derived temperature data, which have been validated from spectroscopic data as well. This study thus highlights the importance of using high-resolution IIRS data for such studies in future.

References: [1] Chowdhury et al. 2020, Current Science, 118, 368–375. [2] Bose et al. 2024, Advances in Space Research, 73, 2720-2752. [3] Verma et al. 2022, Icarus, 383, 115075. [4] Kramer et al. 2013, Icarus, 223, 131-148. [5] Kring et al. 2021, Advances in Space Research, 2021, 4691-4701.

How to cite: Bose, S., Karunakaran, D., Kapadia, T., Panwar, N., and Srivastava, N.: High-resolution surface temperatures of the Moon derived from Imaging Infra-Red Spectrometer (IIRS) on-board Chandrayaan-2: A case study on the Schrödinger Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-691, https://doi.org/10.5194/egusphere-egu25-691, 2025.

In planetary exploration, once a landing site has been selected and a mission has successfully landed, one of the next decisions will be sampling location. Stationary missions that do not have the benefit of mobility, such as pathfinding landers to ocean worlds like Europa, and those limited by surface lifetime, will require some degree of autonomy in the selection of sampling locations within a reachable workspace (Hand et al., 2022). Therefore, the process of sample location selection is worth constraining.

In this work, we investigate Apollo 16 and 17 sampling sites, treating the Moon as our best Europa analogue. We use archival reports, imagery, and other data of four Apollo 16 and three Apollo 17 sites and their corresponding drive tube core samples to constrain how the surface appearance of sampling sites couples with subsurface geology. The surface and subsurface geology are summarized using bin classifications for grain size and shape as first-order representations of regolith formation processes, and then compared with each other and contextualized by descriptions of the astronauts’ sampling decision-making to understand the impact factors in sampling the surfaces of worlds like the Moon. The work is relevant to other data-constrained, short-lived surface sampling missions that will rely on autonomy, as well as future human sampling activities during crewed exploration (e.g., the Artemis program).

References

How to cite: Persaud, D. M., Phillips, C. B., and Hand, K. P.: Legacies and Lessons: Learning from Apollo 16 and 17 sampling for future autonomous planetary exploration, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20197, https://doi.org/10.5194/egusphere-egu25-20197, 2025.

A sizeable fraction of solar wind protons precipitating onto the lunar surface is backscattered from the lunar surface. Additionally the lunar surface is sputtered by the precipitating particle populations. Previous observations by spacecraft from orbit (Chandrayaan-1, Kaguya, IBEX) and from the lunar surface (Chang'e-4) show that up to 20% of the impinging solar wind protons are backscattered as energetic neutral atoms and about 0.1% to 1%  are backscattered as protons. However, particles emitted from the surface can have any charge state. The recent discovery of negative ions by the Negative Ions at the Lunar Surface (NILS) instrument on Chang'e-6 allows for the first time to investigate the full charge state distribution of solar wind induced backscattered and sputtered particle populations from the lunar surface. We present and interpret new data obtained from the lunar surface and discuss the impact of the emitted particle populations on the lunar exo-ionosphere.
 

How to cite: Wieser, M., Canu-Blot, R., Barabash, S., Zhang, A., Stenberg-Wieser, G., and Wang, W.: Emission of negative ions, positive ions and energetic neutral atoms from the lunar surface caused by solar wind precipitation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11607, https://doi.org/10.5194/egusphere-egu25-11607, 2025.

The current renaissance in lunar exploration, driven by space agencies as well as the private sector, requires suitable test and training facilities on Earth to proceed in a safe and sustainable manner. To address this need, DLR and ESA have opened the Moon analogue facility LUNA in Cologne, Germany, in September 2024. We will provide an overview of LUNA and report on first campaigns, which already included usage by universities, national space agencies, and the private sector.

At the heart of LUNA is a 700 m² regolith hall, filled with Mare simulant EAC-1A to 60 cm depth. With black walls, a preliminary sun simulator allowing to simulate illumination at the lunar south polar region, geologically relevant rocks, an Argonaut lunar lander mock-up, two 3U-rovers that might carry individual instruments, and a future gravity offloading, LUNA simulates the lunar surface and allows to test the operations of instruments and experiments on the Moon as well as train operations for robotic and crewed lunar missions. A dedicated ground segment permits commanding and telemetry and data exchange under mission-like conditions. Further outfitting by elements both within (e.g. a ramp to simulate slopes of at least up to 40 deg) and outside of LUNA (e.g. Flexhab habitat, EDEN-LUNA greenhouse) is ongoing.

The deep floor area (DFA), with a regolith depth of up to 3 m over an area of approximately 135m² and two sloping walls with angles of 25° and 40°, allows for testing geophysical exploration methods as well as drilling and sampling techniques. The initial outfitting of the DFA includes two buried metal reference targets for ground-penetrating radar (GPR), as well as a small simulated lava tunnel at the bottom, constructed from concrete and expanded foam sheets. Additionally, PMMA (aka Plexiglas™) is used to simulate the elastic and dielectric contrasts between regolith and ice, which is of special interest in exploration of the lunar South Pole, and emplaced to mimic both a thin ice horizon as well as distributed veins of ice (reticular chaotic cryostructure, formed by 1000 PMMA discs). A fiber-optic cable, including fibers for distributed temperature sensing (DTS), distributed acoustic sensing (DAS), and an engineered fiber, has been buried throughout the hall to be used for background data, and a broad-band seismometer has been installed permanently in LUNA. Several seismic reference measurements as well as a GPR test have been conducted to characterize the LUNA hall and environment.

The EAC-1A simulant has been characterized in terms of elastic, electric and thermal properties, e.g. seismic wave velocities and attenuation from resonant column tests, dielectric permittivity and loss tangent, and thermal conductivity. We show in how far these parameters match the values for actual lunar regolith. We will also report on first test campaigns, e.g. regarding geophones and the engineered DAS fibre, GPR, and rover navigation.

How to cite: Knapmeyer, M., Knapmeyer-Endrun, B., Maibaum, M., Fantinati, C., Hallinger, M., Küchemann, O., Vrettos, C., Plettemeier, D., Benedix, W.-S., Casademont, T. M., Seeling, J., Knollenberg, J., Hart, J., Pinzon Rincon, L. A., Jousset, P., Krawczyk, C., Garcia, R. F., Calosci, L., and Spichal, C.: First campaigns and future developments in the LUNA Moon analog facility, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19008, https://doi.org/10.5194/egusphere-egu25-19008, 2025.