Key events in the early history of the Moon include its formation by a giant impact, the solidification of the lunar magma ocean, and late accretion. The ¹⁸²Hf-¹⁸²W system (t_1/2 ~9 Ma) constitutes a versatile tool to study each of these processes because they can all result in measurable ¹⁸²W variations. Here we review the ¹⁸²W record of lunar rocks and highlight key constraints on the early evolution of the Moon. Tungsten isotope studies on lunar samples demonstrate that there are no resolvable ¹⁸²W variations within the Moon, implying that lunar magma ocean differentiation later than ~70 Ma after Solar System formation. Nevertheless, the Moon is characterized by a uniform ~25 parts-per-million ¹⁸²W excess over the present-day bulk silicate Earth (BSE). One possibility is that this ¹⁸²W difference is radiogenic in origin, in which case the Hf-W system can potentially be used to date the formation of the Moon. However, this interpretation is problematic for two reasons. First, mixing processes during the giant impact very likely modified the ¹⁸²W composition of the Moon and led to distinct initial ¹⁸²W compositions of the Moon and Earth. Second, the pre-late accretion ¹⁸²W compositions of the Moon and BSE overlap within uncertainty, and hence there is no resolved radiogenic ¹⁸²W difference between the BSE and the Moon. Consequently, the Hf-W system does not provide reliable constraints on the age of the Moon. Instead, the Hf–W systematics are fully consistent with 'young' ages of the Moon, well after the effective lifetime of ¹⁸²Hf.

How to cite: Kruijer, T., Archer, G., and Kleine, T.: Tungsten isotopes and the early evolution of the Moon, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8116, https://doi.org/10.5194/egusphere-egu23-8116, 2023.

The 64 km wide Ohm crater is a complex impact crater located on the northern side of the lunar farside. In this study, we generated abundance maps for FeO and TiO₂ as well as Spectral Parameter maps to determine the composition. Orthopyroxene and Clinopyroxene, two mafic minerals, are present in the Ohm crater, according to spectral analyses of M³ data. A geostatistical technique is used to optimize the variation trend of diagnostic characteristics across different sites. We noticed that Opx dominates the rest of the crater, while Cpx dominates the western portion of Ohm. Opx denotes sources from above and/or below the crust-mantle boundary, whereas Cpx suggests impact melt crystallization of an anorthositic target crust. The NASA mission GRAIL, which is specifically designed to study gravity anomalies, has found negative anomalies near the Ohm crater that may indicate a thicker crust beneath the crater. Unequal Bouguer gravity anomalies and negative anomalies have been found in the vicinity of the Ohm crater, but they are not clearly connected to the internal morphology. Surface morphological features have no connection to these anomalies of uneven gravity. In addition, the Bouguer gravity signature may be affected by pre-existing subsurface density structure, and post-impact events (such as magmatism), which could account for some of the observed scatter. The regional gravity anomaly also indicates low values in the Ohm crater, suggesting that the thicker crust and the source of the geochemical anomalies are at deeper levels. Strong negative anomalies are seen in the predicted residual gravity data close to the Ohm crater, which suggests low-density bodies at the crustal level. We propose that the pyroxenes are the end product of impact melt crystallization based on regional and residual gravity anomalies, compositional and mineralogical features of the Ohm crater, and geophysical data. Ejecta from the SPA, Orientale, and Mascon Hertzsprung basins, which may or may not have differed from impact melt formed during the Ohm impact event, should also be looked at when analyzing the distribution of mafic minerals throughout the crater. The GRAIL crustal thickness model-1 for the Ohm crater indicates a thicker crust, demonstrating that the mantle upliftment is not the underlying cause of the geochemical anomalies in this area.

Acknowledgement: S. M. Patel and M. R. El-maarry acknowledge support for this work through an internal grant (8474000336-KU-SPSC).

How to cite: Patel, S., Satyakumar, A. V., Solanki, P., and El-maarry, M. R.: Mafic Mineral Anomaly in the Ohm Crater of the Moon, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5929, https://doi.org/10.5194/egusphere-egu23-5929, 2023.

Boulders are a major surface feature on solid planets and small bodies, including asteroids and comets. Interest in these clasts range from applications relevant for landing site selection to geomechanical parameter characterization of the soil on which they rest [1], to measurements of their size frequency distributions [2] which is relevant for an understanding of their formation and erosion processes. On the Moon boulders are generally found in association with craters, hilltops, rilles, and other steep relief forms. Two main mechanisms of boulder formation are bedrock fragmentation and excavation by impacts, and progressive exposure of pre-existing blocks and fractured bedrock by removal of regolith from steep reliefs by diffusive creep.

An important issue are transport processes which can move the stones on the surface of their parent bodies. On the Moon, one group of boulders, frequently called “rolling stones”, have left tracks on the surface which can cover large distances. Mainly two mechanisms, meteoritic impact and moonquakes [3], have been cited in the literature as drivers of boulder displacements. Much less attention has been given to the hypothesis that other processes like thermal solar-induced rock breakdown [4] could deliver the initial momenta that could initiate the movement of meta stabile rocks.

From an AI -based mapping of the distribution of boulders with tracks on the lunar surface [5] we know that the majority of these boulders are found – not surprisingly - within craters. However, as the AI-based procedure strongly underestimated the number of boulders with tracks, we have conducted a new investigation to map these boulders. However, such a mapping it is only one prerequisite in understanding whether a thermally-induced breakdown could be responsible for an initial triggering of boulder movements. Boulders moving down the slopes disturb the mature regolith and move fresh lunar soil to the surface. This process should remotely be detectable through the stronger spectral features of the fresher optically immature regolith. The number of non-decayed boulders along crater walls should therefore be correlated with the strength of the absorption bands in spectra taken from those crater walls. Spectral characteristics of the refreshed crater walls are measurable through various quantities in the VIS-NIR (e.g. color ratios, etc.)

To start addressing the question to what extent a solar-induced breakdown can trigger rock movements, we have chosen lunar craters for which we have generated new boulder maps. For these craters we determine spectral characteristics and mineralogical composition based on a nonlinear spectral mixing model using M3 hyperspectral imager data from Chandrayaan-1. We are reporting the first results of spectral feature mapping for these craters and discuss the mineralogical interpretation, as well as the existence of a correlation between the number of observable boulders inside craters and identified spectral features of the regolith.

References:

[1] Filice, A., 1967, Science, 1967-06-16 156(3781): 1486-1487. [2] Ruesch, O. et al., 2022 Icarus, 387, 115200. [3] Kumar, S. et al., 2016, J. Geophys. Res. Planets, 121, 147– 179. [4] Molaro, J.L. et al., 2017, Icarus, 294, 247-261. [5] Bickel, V.T. et al., 2020, Nat Commun 11, 2862.

How to cite: Mall, U. and Surkov, Y.: Are day-night heating cycles a trigger for launching the “stones” on tour?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10887, https://doi.org/10.5194/egusphere-egu23-10887, 2023.

Over the last few decades, observations have revealed the presence of water ice at the lunar poles and upended the notion of a completely dry lunar surface. These ice deposits hold information about the history of water on the Moon and in the Earth-Moon system, and are potential resources for future human exploration of the Moon. However, they remain relatively uncharacterized in abundance, distribution, and composition. Foremost among the open questions about lunar ice are: What were the sources of ice on the Moon’s surface, and how much water could have been delivered? The three most likely sources of lunar water ice are: (1) impact delivery from asteroids and/or comets, (2) solar wind ion implantation, and (3) volcanic outgassing of volatiles from the lunar interior. Here, we assess the viability of a volcanic source for water ice accumulated at the lunar poles.

[1] first suggested the occurrence of a volcanically induced transient atmosphere on the ancient Moon that would have been dominated by CO, but with a significant amount of H­₂O. Further studies investigated the dynamics [2] and atmospheric escape processes [3] that would have affected such an atmosphere. [4] later suggested that a large number (30,000-100,000) of eruptions would have created less massive atmospheres during the Moon’s most volcanically active period (4-2 Ga).

We model the generation of transient atmospheres from 50,000 eruptions from 4 to 2 Ga, the subsequent escape of these atmospheres to space, and the concurrent accumulation of atmospheric water vapor as ice at the lunar poles [5]. The molecular composition of the modeled atmospheres is determined using estimates of outgassed volatile content for lunar volcanic eruptions derived from analyses of Apollo samples [4,6]. We model three atmospheric escape processes: (1) Jeans escape, (2) sputtering escape, and (3) photodissociative escape [3], and model photodissociative escape separately for both CO and H₂O. We use maximum annual surface temperatures [7] measured by the Diviner Lunar Radiometer Experiment on board the Lunar Reconnaissance Orbiter [8] to calculate ice accumulation rates for each Diviner pixel within 30° latitude of the poles [5].

We find that water vapor is removed from a typical transient atmosphere in about 50 years via ice accumulation and photodissociative escape. About 41% of the total water vapor mass outgassed from 4 to 2 Ga is accumulated as ice on the surface. This demonstrates that a significant amount of ice (~8×10¹⁵ kg) could have been sourced from volcanic outgassing, though atmospheric escape processes also strongly control the efficacy of this mechanism.

[1] Needham, D. H. and Kring, D. A. (2017) EPSL, 478, 175-178. [2] Aleinov, I., et al. (2019) GRL 46, 5107-5116. [3] Tucker, O. J., et al. (2021) Icarus, 359, 114304. [4] Head, J. W., et al. (2020) GRL, 47, e2020GL089509. [5] Wilcoski, A. X., et al. (2022) PSJ 3.5, 99. [6] Rutherford, M. J., et al. (2017) Amer. Mineralogist, 102, 2045-2053. [7] Landis, Margaret E., et al. (2022) PSJ 3.2, 39. [8] Paige, D. A., et al. (2010) Space Sci. Rev., 150, 125- 160.

How to cite: Wilcoski, A., Hayne, P., and Landis, M.: Polar Ice Accumulation from Volcanically Induced Transient Atmospheres on the Moon, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11166, https://doi.org/10.5194/egusphere-egu23-11166, 2023.

This work studies the remanent magnetization under a weak and a strong magnetic anomaly in Tranquillitatis and in Oceanus Procellarum respectively, which show similar surface ages of 3.6 Ga and 3.3 Ga. A 3D amplitude inversion is used to reconstruct the distributions of magnetization underground. Since there is no globally measured surface magneticeld for the Moon, a crustal magnetic anomaly model with grid resolution of 0.2° is used. The depth to the bottom of the magnetic source is fixed by the boundary identified by a relative criterion, which is 20% of the recovered maximum magnetization. The results show that the two anomalies have different depths to the bottom and different volumes of magnetic sources. The depth to the bottom of the magnetic carriers, which is possibly the Curie depth, is about 30 km and 50 km under Oceanus and Tranquillitatis. The volumes of the two magnetic sources are at the scale of 10⁴ and 10⁵ km³, respectively. The Bouguer gravity anomalies with spherical harmonics reaching 1200 degree in the two studied regions are also checked. The results supports that the magma intrusions containing different abundances of metallic iron are the most possible origins of the magnetic sources in the studied regions. Besides, the thermal states of lunar crust under the two studied maria were probably different during the acquisition process of remanent magnetization.

How to cite: Wang, H. and Yao, S.: Depths to the Bottom and Volumes of Magnetic Sources under a Weak and a Strong Lunar Magnetic Anomaly Revealed by 3D Inversion, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3164, https://doi.org/10.5194/egusphere-egu23-3164, 2023.

Within the pre-phase A of the Moonlight project proposed and funded by the European Space Agency (ESA), the ATLAS consortium has proposed an architecture to support a Lunar Radio Navigation System (LRNS) capable of providing PNT (Positioning, Navigation, and Timing) services to various lunar users. The Moonlight LRNS will be a powerful tool in support of the lunar exploration endeavors, both human and robotic.

The ESA LRNS will consist of a small constellation of 3-4 satellites put in Elliptical Lunar Frozen Orbits (ELFO) with the aposelene above the southern hemisphere to better cover this region, given its interest for future lunar missions. This LRNS will be supported by a ground station network of small dish antennas (~30 cm), which can establish Multiple Spacecraft Per Aperture (MSPA) tracking at K-band. Any Earth station will be capable of sending a single uplink signal to multiple spacecraft thanks to Code Division Multiplexing modulation, while in the downlink multiple carriers can share the same K-band bandwidth by implementing Code Division Multiple Access (CDMA) on the onboard transponders. This allows the implementation of the Same Beam Interferometry (SBI) technique [1], which adds to spread spectrum ranging and Doppler measurements. In the scope of disseminating accurate PNT services to end users, the constellation will also be capable of maintaining a synchronization to the Earth station clocks to the ns level.

The performances of the proposed architecture have been validated through numerical simulations performed with the ESA GODOT software, enhanced with additional user-defined features and capabilities. For each satellite of the LRNS constellation, the attainable orbital accuracy is at level of a few meters for most orbit mean anomalies and it has been computed considering a setup which includes a perturbed dynamical model (mainly coming from uncertainties in the accelerations induced by the solar radiation pressure and orbital maneuvers) and a realistic error model for Doppler, ranging and SBI measurements.

REFERENCE:

• Gregnanin, M. et al. (2012). Same beam interferometry as a tool for the investigation of the lunar interior. Planetary and Space Science 74, 194-201

How to cite: Sesta, A., Di Benedetto, M., Durante, D., Iess, L., Plumaris, M., Racioppa, P., Cappuccio, P., di Stefano, I., Pastina, D., Boscagli, G., Molli, S., De Marchi, F., Cascioli, G., Sosnica, K., Fienga, A., Linty, N., and Belfi, J.: Orbit Determination and Time Transfer for a Lunar Radio Navigation System, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15933, https://doi.org/10.5194/egusphere-egu23-15933, 2023.

The lunar heat-flow ultra-wideband spectrometer operates over an extended frequency band from 300 MHz to 6.0 GHz. It is a direct-acquisition single-chain digital spectrometer measuring 1024 spectral channels over 6 GHz bandwidth with each channel bandwidth about 6 MHz. The LHR instrument is intended to characterize the near surface regolith thermal and dielectric properties in order to determine the local geothermal heat flux. It would also reveal subsurface thermal and dielectric property changes due to buried ice, dielectric materials like ilmenite, and bedrock. The wide spectral bandwidth is expected to provide up to 1 m deep brightness temperature measurements from as close as 5 cm penetration depth at higher frequency end of the spectra. Using information obtained at multiple frequency bands, the subsurface temperatures and dielectric properties can be reconstructed.

The instrument is currently being developed at Jet Propulsion Laboratory in Pasadena, CA. The design includes a novel receiver architecture allowing a single chain design for the ultra-wideband channelized spectral operation for enabling the science objectives of the instrument. The lab-bench demonstration of the lunar spectro-radiometer has been performed including the calibration testing. The environmental testing will be further conducted before proceeding with the flight model. The final flight version of the spectro-radiometer instrument is expected to have light weight, low-power and small-size suitable for a deployment into a lunar rover or lander.

How to cite: Ogut, M., Brown, S., Tanner, A., Misra, S., Ruf, C., Chen, C.-C., and Siegler, M.: An Ultra-Wideband Spectrometer for Lunar Heat-Flow Measurements, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10737, https://doi.org/10.5194/egusphere-egu23-10737, 2023.

With NASA’s increased focus on exploration of our Moon within the Artemis program, new scientific goals have been formulated to expand our knowledge on the history of our Solar System, including the evolution of the Earth-Moon system. Additionally, establishing a permanent human presence on the Moon has been declared a goal of the Artemis program, the success of which will inevitably depend on in-situ resource utilization (ISRU) of lunar material. In turn, successful ISRU requires methods capable of analysing and selecting suitable materials in place. To support these tasks, sensitive instrumentation capable of determining the elemental and isotope composition of geological samples from the lunar surface is essential. Consequently, defining and determining the technical requirements of such instrumentation, constructing it accordingly, and verifying its performance are all crucial steps in maximising the scientific return of such a mission. Furthermore, NASA’s Artemis program also aims to facilitate future human exploration of Mars, which implies that instrumentation applied successfully on the Moon might find its application on the Martian surface in the future.

We present our progress in designing, constructing and testing a prototype miniature laser ablation ionisation mass spectrometer (LIMS) for in-situ measurements on the lunar surface. The finalised instrument will be deployed on the Commercial Lunar Payload Service (CLPS) mission CP-22 scheduled for launch in late 2026 and land in the lunar south pole region. Our miniature reflectron-type time-of-flight mass analyser (160 mm x Ø 60 mm) designed for in-situ space applications was coupled to a pulsed Nd:YAG microchip laser system (SB1 series, Bright Microlaser Srl, Italy) operating at 532 nm (max. laser pulse energy of 40 µJ, pulse repetition rate of 100 Hz). The laser source and the optics were mounted colinearly to the optical axis of the instrument assembly into a cage system. This construction is modelled after the envisioned flight design, and therefore used to determine the required optical and electronic performance characteristics of the future flight instrument. The current flight design will be presented as well. Furthermore, validation of the technical implementation and verification of the scientific requirements will be discussed through the results of laser ablation experiments conducted on lunar regolith simulant.

How to cite: Keresztes Schmidt, P., Blaukovitsch, M., Boeren, N. J., Tulej, M., Riedo, A., and Wurz, P.: Instrumentation for laser ablation ionisation mass spectrometry on the lunar surface, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13387, https://doi.org/10.5194/egusphere-egu23-13387, 2023.

Lunar Vertex is a mission at the intersection of multiple science communities, from planetary geology to space plasma physics. As the first Payloads and Research Investigations on the Surface of the Moon (PRISM1) investigation, scheduled for delivery to the Reiner Gamma (RG) magnetic anomaly in 2024 aboard a commercial lunar lander, Lunar Vertex will unravel the nature of the RG anomaly, the connection to and origin of the associated lunar swirl surface feature, and the structure and impact of the “mini-magnetosphere” in this region. Lunar Vertex includes a suite of magnetometers (Vector Magnetometer – Lander; VML), a fixed-mounted set of cameras (Vertex Camera Array; VCA), and a low-energy ion and electron plasma analyzer (Magnetic Anomaly Plasma Spectrometer; MAPS) on the lander. In addition, a second suite of commercial fluxgate magnetometers (Vector Magnetometer – Rover; VMR) and a multispectral imager (Rover Multispectral Microscope; RMM) are mounted on a dedicated rover that will traverse a distance of at least 500 m from the lander, providing additional multi-point measurements. The combination of magnetic field measurements taken during cruise and descent by VML and during surface operations by both VML and VMR will characterize the surface magnetic field within a strong lunar magnetic anomaly. The combined magnetic field and plasma measurements from VML and MAPS will provide direct observations of plasma populations reaching the lunar surface and the associated local magnetic field configuration. Furthermore, the lunar regolith within the RG magnetic anomaly and over different regions of the associated lunar swirl will be characterized by RMM and VCA to reveal the surface texture, composition, and particle distribution around both the lander and rover locations and the correspondence to potential surface weathering processes.

How to cite: Vines, S., Ho, G., Blewett, D., Halekas, J., Greenhagen, B., Anderson, B., Waller, D., Jahn, J.-M., Kollmann, P., Denevi, B., Meyer, H., Klima, R., Cahill, J., Hood, L., Tikoo, S., Zou, X.-D., Weiczorek, M., Lemelin, M., Fatemi, S., and Cloutis, E.: Lunar Vertex: A PRISM Science Investigation of the Reiner Gamma Lunar Magnetic Anomaly and Swirl, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10526, https://doi.org/10.5194/egusphere-egu23-10526, 2023.

Recently, NASA’s InSight mission has shown the value of geophysical landers by greatly increasing our knowledge of the interior of Mars. Correspondingly, geophysical experiments are also of great relevance to lunar exploration: a number of geophysical experiments were proposed in response to the ESA's 2020 call for ideas for a scientific utilization of the large logistics lander (Argonaut). Geophysical payloads are already planned for the Moon, e.g. the Farside Seismic Suite will land a broad-band seismometer in 2025. We here present how the LUNA Habitat training facility under construction in Cologne, Germany, can contribute to the development and testing of lunar geophysical instrumentation.

The about 700 square meters of the LUNA Habitat will be covered by 60 cm of EAC-1 regolith simulant on most of the area. On an area of 140 square meters, regolith depth increases to 3 m along a sloping bottom (25° and 40°). This part of LUNA provides an invisible, but explorable underground structure suitable for seismic profiling, ground penetrating radar, geoelectrics, geomagnetics and other techniques, as well as sufficient depth for drilling, subsurface sampling, and deployment of heat flow probes. Sculpting craters and even caves in the regolith, as well as cooling small portions of it, is envisioned. Support by the facility will include personnel with experience in geophysical measurements and data analysis, an end-to-end operational environment including a remote control center with standard communication technology, and, last but not least, training of astronauts in co-operation with robotic units to operate the equipment in lunar surface suits and under gravity offloading.

A four-element, Y-shaped array of short period seismometers, based on the layout of the Apollo 17 seismic experiment, will be deployed on the LUNA construction site before erecting the building to record seismic noise sources (car traffic on the DLR campus, the ENVIHAB short arm centrifuge, wind tunnel discharges, air traffic on the nearby CGN international airport etc.). It will also allow for ambient noise analysis aimed at the underground structure, which is expected to consist of Rhine sediments. An active refraction seismic experiment and the deployment of 12 nodal sensors will further aid in site characterization. LUNA will have a concrete floor of up to 60 cm thickness, but with a structured underside for static reasons. The array will be re-deployed on the concrete once the hall is erected to characterize in how far the new high-velocity layer hides the underlying sediments from seismic observation. After completion of LUNA, the effect of the regolith cover on seismic recordings will be characterized by a third array deployment. Documentation of construction details, especially steel enforcing in the concrete, is foreseen.  A broad-band seismometer will be installed in the LUNA Habitat permanently, once construction is finished, to support the identification of artificial noise sources and local seismicity in the recordings of customer instruments, and monitor possible changes in the background e.g. due to new buildings or other large-scale research facilities on the DLR campus.

How to cite: Knapmeyer, M., Knapmeyer-Endrun, B., Maibaum, M., Biele, J., Fantinati, C., Küchemann, O., Ulamec, S., and de Vera, J.-P.: The ESA/DLR LUNA Habitat as geophysical experimentation facility, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5040, https://doi.org/10.5194/egusphere-egu23-5040, 2023.