Lunar volcanic pits are collapse features that open a window into the Moon's subsurface and, with that, into its geologic past. Accessible subsurface space might also provide protection to future permanent lunar infrastructure. However, the exploration of pits presents a significant engineering challenge, largely due to the stark topographic gradients around pits, including funnel slopes approaching the angle of repose of regolith, vertical pit walls, and terrain cluttered with boulders. These characteristics have a direct, negative effect on one key element of lunar exploration missions: continuous Line-of-Sight (LoS) between a mobile asset on the surface and a lander or orbiter, which is particularly important for small robotic missions with small antennas and power budgets. Here, we develop and demonstrate two algorithms that can characterize and quantify LoS around prospective landing sites and pits. First, we implement a viewshed algorithm on Digital Terrain Models to assess LoS as a function of asset and lander geometry for 8 selected lunar mare pits with suitable landing sites and available DTMs to aid regional-scale landing site assessment. We identify several pits with promising LoS characteristics and map out optimal lander locations that provide up to 90.3% LoS coverage, such as a potential landing site at i at = 14.085 degrees and ion = 303.222 degrees near the Marius Hills pit. Second, we use ray-casting and a geometric model of the Marius Hills pit to characterize how assets with different camera viewing geometries are able to map out the pit wall and an anticipated cave for a range of terrain navigationconstraints, with a focus on slope angle. Our analysis suggests that an asset would be able to view as deep as 15 m into the Marius Hills pit from most observation locations without moving onto funnel slopes steeper than similar to 5 degrees. A dedicated pit explorer such as the LunarLeaper mission could resolve the anticipated cave at a depth of similar to 30 m with a camera at similar to 0.7 m above the ground, moving on a funnel slope of about similar to 10 degrees. Our analysis and algorithms close a key capability gap and directly inform future landing-site selection and traverse planning efforts.

The NASA InSight mission observed over 2000 marsquakes in the course of its three year mission. These quakes varied in magnitude between 1.5 and 4.5, as well as in spectral content. We present a simple framework to describe the spectral characteristics of all observed marsquakes, based on source process; propagation through the mantle or crust; and local, receiver-side amplification. We assign to each quake an objective measure of its amplitude, as well as the spectral decay created by the duration of the rupture and the dampening of high frequencies due to visco-elastic attenuation. Together, this allows us to obtain characteristic patterns of the whole marsquake dataset, e.g. in terms of event magnitudes, source size, and - for quakes caused by meteoritic impacts - crater size. We show that a significant fraction of all marsquakes - the high-frequency quakes - form a swarm that is likely not caused by tectonic processes in rocks. Our analysis allows separation of the whole marsquake catalogue into three event classes, of tectonic quakes, meteoritic impacts, and swarm events. We finally conclude that the largest marsquake, S1222a, most likely belongs to the group of meteoritic impacts.

SUMMARY X. Huang et al. reported the detection of 67 teleseismic marsquakes identified by P- and S-wave arrivals. The authors used a deep learning phase picker trained on local earthquake data and applied it to narrow-bandpass filtered seismic data recorded by NASA’s InSight seismometer, making use of similarities between local earthquake and teleiseismic marsquake recordings when adjusting for sampling rate and S-P timescaling relations. We review all detections as similarly done for the Marsquake Service catalogue and other studies on this data set, using the complementary wind and pressure data recorded by InSight. As these auxiliary data were not recorded in the second half of the mission, we also infer wind contamination from bandwidths in the seismic data that contain wind-sensitive lander modes. Additionally, we analyse the signal polarization to compare it with the expected characteristics of P and S waves and the background noise. Our review indicates that all 67 detections reported by the authors correspond to atmospheric noise. In most cases, the detections relate to the seismic signature of small wind bursts followed by larger wind bursts, onsets of which are interpreted as P and S waves by the authors. Further, we show that if these events were interpreted as genuine marsquakes, their inferred epicentral distance distribution would not match typical marsquake distances, while their magnitudes would make them the largest events of the catalogue. For future studies that deal with seismic event detection and interpretation from InSight, we recommend a careful consideration of the established event and noise signal markers described in this comment and in the literature to avoid misinterpretation of noise as event signals.

NASA's InSight mission has provided an unprecedented snapshot of Mars' seismicity, despite data analysis challenges arising from low signal-to-noise ratios (SNR) and single-station constraints. High frequency (HF) events-the most common type-were initially assumed to propagate through shallow crustal layers. However, several impacts that occurred late in the mission provided independent distance constraints, indicating that HF event energy must have propagated through the mantle. We analyzed the full HF data set using an extended catalog and denoised waveforms derived with deep learning (DL) techniques. Using a DL ensemble, we picked phase arrivals on denoised envelopes and estimated SNR-dependent pick timing uncertainties based on the removed noise. We computed distances consistent with mantle paths using the latest Mars interior models, while the back azimuth remained inconclusive due to local resonance dominating the HF bandwidth. We compared and grouped HF recordings by their similarity and investigated how attenuation properties shape their envelopes. Additionally, we re-calibrated and assigned magnitudes for the extended catalog. Overall, we (re-)located 1,430 HF events clustered between epicentral distances of around 1,600-3,600 km, but without constraints on the back azimuth, their source region remains speculative. Based on spatiotemporal similarities, we attributed a subset of 1,357 events to a common source region and labeled them as swarm events. The analysis of envelope shape confirms and extends previous results of stratified attenuation properties. Swarm events, with magnitudes between 1.5 and 2.5, are cumulatively equivalent to a single magnitude 4 event and show a high -value and clear seasonal trends in seismicity.

We present the LunarLeaper mission concept, which aims to robotically investigate volcanic pits on the lunar surface. Volcanic pits, or skylights, are collapse features that may provide access to subsurface lava tubes, which could serve as shelters for future human explorers and offer insight into the volcanic history of the Moon by exposing ancient lava flows. The existence and extent of large caves are still debated today and require in situ analysis. The Marius Hills site in particular offers a potential entry point to a cave system in a volcanic region on the lunar nearside. Our mission aims to deploy a payload-equipped 15kg-class legged robot that can approach a pit, such as the Marius Hills pit, while taking measurements during the traverse. During the mission, measurements from a ground-penetrating radar (GPR) and a gravimeter will allow us to survey the subsurface and map any underlying lava tube, if present. The mission will investigate key questions regarding lunar volcanism, such as the existence and geometry of subsurface caves and the magnitude and timing of lava flows, while assessing the site’s suitability for future human utilization and habitation. Furthermore, the mission will demonstrate key enabling technologies such as legged robots, serving as building blocks for the next generation of planetary missions.

We present LunarLeaper, a robotic explorer concept in response to the ESA 2023 Small Missions call. Pits, volcanic collapse features with near-vertical walls, have been identified across the lunar and Martian surface. These pits are high priority exploration destinations because some, referred to as skylights, might provide access to subsurface lava tube systems. Lava tubes are of particular interest for future human exploration as they offer protection from harmful radiation, micrometeorites and provide temperate and more stable thermal environments compared to the lunar surface. We propose to use a small legged robot (ETH SpaceHopper,

Understanding the elastic properties of Earth's inner core is crucial for unraveling its role in the planet’s evolution and dynamics. Seismic shear waves provide a direct means to constrain the shear modulus of the solid inner core at high frequencies. However, their detection has been challenging due to their extremely weak amplitude and interference from other seismic arrivals (Doornbos, 1974). This study aims to provide direct observations of inner-core shear waves through a systematic search using the AlpArray Seismic Network (AASN), a large European seismic array. The approach combines 3-C polarization filtering and slant-stacking techniques. The inspection focuses on events between 2015 and early 2022 within the epicentral distance range of ~110-150° from the AASN. This source-receiver geometry is close to that of previous PKJKP observation reported using the Gräfenberg array (Cao et al., 2005).Our systematic search and classification reveal multiple potential observations of PKJKP at frequencies > 0.1 Hz, consistent in both time and slowness with the 1-D Earth model ak135, as well as previous body-wave-based observations, particularly Wookey and Helffrich (2008). The new evidence of PKJKP demonstrates a path forward for formalizing a method for the repeatable detection of inner-core shear waves for different source-receiver geometries. Additional PKJKP observations and comprehensive modeling are essential for gaining insights into the intricate inner-core structure and phenomena, such as anisotropy and focusing effects, which could explain the limited number of observations to date.

With the selection of multiple missions to Venus by NASA and ESA that are planned to launch in the coming decade, we will greatly improve our understanding of Venus. However, none of these missions have determining the seismicity of the planet as one of their primary objectives. Nevertheless, constraints on the seismicity remain crucial to understand the tectonic activity and geodynamic regime of the planet and its interior structure. Funded by the International Space Science Institute (ISSI) in Bern, Switzerland, we have gathered an interdisciplinary team of experts in seismology, geology, and geodynamics to assess the potential seismicity of Venus, specific regions that could be seismically active at present, and the methods to detect them.Here, we present the findings from our second ISSI team meeting (January 29 - February 2, 2024), aiming to review knowledge on Venus's seismicity and interior and identify the best approaches for future missions. We present the feasibility, advantages, and disadvantages of different seismic observation techniques on the surface (e.g., broadband seismometers, distributed acoustic sensing methods), from a balloon (acoustic sensors), and from orbit (airglow imagers). We make a recommendation for the instrumentation of a future seismology-focused mission to Venus. We also suggest target regions with a high likelihood of significant surface deformation and/or seismicity. These targets are useful for the upcoming VERITAS (Venus Emissivity, Radio Science, InSAR, Topography and Spectroscopy) and EnVision missions and would specifically benefit from the repeat pass interferometry of VERITAS, which detects surface deformation and can therefore in principle constrain the maximum displacement of surface faulting at locations that are visited twice during the mission.

Seismic events (icequakes) associated with floating ice sheets on lakes are a frequently observed phenomenon. We find at our study site on the frozen Lake St. Moritz in the Swiss Alps typically a clear diurnal pattern with hundreds to thousands of icequake signals per hour during night time, while the rate of observed events during daytime is about two orders of magnitude smaller. The seismicity rate shows a significant correlation with temperature changes. It is therefore assumed that the generation of the ice quakes is related to melting and freezing processes as well as the extension and contraction of the ice. Potentially the seismicity rate is also moderated by loading and unloading due to human activities on the ice and/or lake level changes. These ice quakes generate seismic waves that propagate through the thin ice sheet as plate waves modulated by the air and water half-spaces above and below the ice (quasi-guided waves). One member of this wave-type family, the quasi-Scholte waves, are characterised by distinct dispersion that can be observed with seismic sensors on the ice. Furthermore, the seismic waves traveling through the ice couple into the air leading to audible seismo-acoustic signals. One particularity of the ice-air coupling is a so-called coincidence phenomenon. The particular velocity-frequency combination where the seismic wavelength in the ice matches the apparent acoustic wavelength in the air leads to a resonance phenomenon. Observation of the related coincidence frequency allows us, for example, to infer on the ice thickness from the acoustic observations with a low cost microphone above the ice only. Recording the acoustic signals with small microphone arrays enables additionally, for example, locating the source of the seismo-acoustic signal. Combined observations of the seismic and acoustic signals provide new insights into the seismicity of lake ice which has rarely been studied in the past. The seismo-acoustic signals have the potential to provide information about the ice properties such as thickness and ice quality as well as waxing and waning processes of ice sheets. These observations are relevant for safe operations on the ice but also to complement other remote-sensing observations with autonomous in situ seismo-acoustic measurements for climate studies.

We present LunarLeaper, a robotic explorer concept in response to the ESA 2023 Small Missions call. Pits, volcanic collapse features with near-vertical walls, have been identified across the lunar and Martian surface. These pits are high priority exploration destinations because some, referred to as skylights, might provide access to subsurface lava tube systems. Lava tubes are of particular interest for future human exploration as they offer protection from harmful radiation, micrometeorites and provide temperate and more stable thermal environments compared to the lunar surface. We propose to use a small legged robot (ETH SpaceHopper, <10 kg), to access and investigate the pit edge, using its ability to access complex and steep terrain more safely than a wheeled rover. LunarLeaper will land in Marius Hills within a few 100 m of the pit and traverse across the lateral extent of the hypothesized subsurface lava tube. On its traverse it will take measurements with a ground penetrating radar and a gravimeter, measurements that will allow us to survey the subsurface structure and detect and map lava tube geometry if present. The robot will approach the pit edges and acquire high resolution images of the pit walls containing uniquely exposed layers of the geophysically mapped lava flows and regolith layers. These images will allow not only scientific advances of lunar volcanism and regolith formation, but also enable assessment of the stability of the pit structure and its use as a possible lunar base. The mission is expected to last 1 lunar day. The robot could be delivered to the surface by a small lander, as they are currently developed and planned by various national and commercial agencies and hop off the landing platform without the need for a robotic arm. It is highly flexible in accommodation and can thus make full use of the new international lunar ecosystem.

The Laser Interferometer Space Antenna (LISA) is a planned space-based observatory to measure gravitational waves in the millihertz frequency band. This frequency band is expected to be dominated by signals from millions of Galactic binaries and tens of merging massive black hole binaries. The LISA Data Challenge 2a is focused on robust signal extraction from a blend of these two types of gravitational wave signals. Here, we introduce a novel high performance and cost-effective global fit pipeline extracting and characterizing galactic binary and massive black hole binary signals and estimate the noise of the residual. We perform the pipeline in a time-evolving weekly analysis starting with an observation time of 1 week until we reach a full year. As expected we detect more galactic binaries and massive black hole binaries bringing the noise estimate of the residual closer to the instrument noise with each week of additional observation time. Furthermore, we present a novel maximum likelihood estimate-based algorithm for extracting multiple massive black hole binaries. Additionally, we demonstrate a massive black hole binary signal extraction with a more accurate LISA response, considering higher harmonic modes, in a noisy data set.

The relatively unconstrained internal structure of Venus is a missing piece in our understanding of the Solar System formation and evolution. To determine the seismic structure of Venus’ interior, the detection of seismic waves generated by venusquakes is crucial, as recently shown by the new seismic and geodetic constraints on Mars’ interior obtained by the InSight mission. In the next decades multiple missions will fly to Venus to explore its tectonic and volcanic activity, but they will not be able to conclusively report on seismicity or detect actual seismic waves.Looking towards the next fleet of Venus missions in the future, various concepts to measure seismic waves have already been explored in the past decades. These detection methods include typical geophysical ground sensors already deployed on Earth, the Moon, and Mars; pressure sensors on balloons; and airglow imagers on orbiters to detect ground motion, the infrasound signals generated by seismic waves, and the corresponding airglow variations in the upper atmosphere.Here, we provide a first comparison between the detection capabilities of these different measurement techniques and recent estimates of Venus’ seismic activity.In addition, we discuss the performance requirements and measurement durations required to detect seismic waves with the various detection methods. As such, our study clearly presents the advantages and limitations of the different seismic wave detection techniques and can be used to drive the design of future mission concepts aiming to study the seismicity of Venus.

Seismic observations of impacts on Mars indicate a higher impact flux than previously measured. Using six confirmed seismic impact detections near the NASA InSight lander and two distant large impacts, we calculate appropriate scalings to compare these rates with lunar-based chronology models. We also update the impact rate from orbital observations using the most recent catalog of new craters on Mars. The snapshot of the current impact rate at Mars recorded seismically is higher than that found using orbital detections alone. The measured rates differ between a factor of 2 and 10, depending on the diameter, although the sample size of seismically detected impacts is small. The close timing of the two largest new impacts found on Mars in the past few decades indicates either a heightened impact rate or a low-probability temporal coincidence, perhaps representing recent fragmentation of a parent body. We conclude that seismic methods of detecting current impacts offer a more complete dataset than orbital imaging.

The surface of Venus presents a large variety of tectonic structures, from rift zones that extend thousands of kilometers [1], to globally spread wrinkle ridges [2] and coronae that could be associated with regional subduction [3]. In addition, there is a growing number of observations that point towards a geologically active Venus at present-day [4,5]. Therefore, it is highly likely that Venus is currently a seismically active planet. Yet, very little is known about the seismicity of Venus, mostly due to the lack of seismic data. Meanwhile, taking other geophysical constraints, we can start investigating some seismic properties of Venus. These analyses are essential for the planning of potential future seismic-focused missions to Venus.A fundamental property to characterize possible seismicity levels of a planet is the thickness of the seismogenic zone, which corresponds to the upper, more brittle part of the planet where rocks can break and release seismic energy. The seismogenic thickness is closely related to the thermal structure of the lithosphere and it is usually defined by an isotherm. This study compiles estimates of lithospheric thermal gradients from geodynamic models and geophysical observations with the goal of obtaining a holistic view of the lithospheric thermal structure and seismogenic zone thickness of Venus. Here we adopt the 600°C isotherm as the seismogenic thickness, based on what has been measured for the Earth [6].We use three independent approaches to investigate the thickness of the seismogenic zone on Venus. In the first approach, we compile a range of local elastic thickness constraints based on flexural analysis using topography and gravity data from different studies [7,8,9,10]. These elastic thickness estimates are then used to compute lithospheric thermal gradients which, in turn, allow us to determine locally the depth of the 600°C isotherm. Considering a strain rate of 1e-16 s-1 and a dry diabase rheology [11] we found that seismogenic thickness values range from 4 to 30 km, as shown in Figure 1a.In a second approach we use 3D geodynamic thermal evolution models to assess the thermal structure of present-day lithosphere considering two distinct end-member magmatic scenarios [12]. In one case, we consider fully extrusive magmatism, i.e., all melt produced in the mantle is extracted to the surface. On the second case, 80% of the melt remains trapped within the lithosphere at 50 km depth. These scenarios lead to completely distinct lithospheric structure (see Figure 1b). Extrusive magmatism builds an extremly thick and cold lithosphere aassociated with seismogenic thicknesses of 60-150 km, while a high level of intrusions results in a thin and warm lithosphere, with seismogenic thickness values of 5-40 km.Finally, we obtain seismogenic thickness estimates associated with constraints on mantle density anomalies from geophysical inversions using gravity and topography data [13]. In this case, the density anomalies are assumed to be caused by mantle temperature anomalies via the relation , where is the thermal expansivity, is the reference mantle density and correspond to latitude and longitude. These mantle temperature anomalies cause temperature variations at the base of the thermal lithosphere which, in turn, affect the lithospheric thermal gradient and the seismogenic thickness. Since these constraints are only sensitive to lateral variations of temperature and not the absolute temperature, to constrain the seismogenic thickness we use the intrusive geodynamic model as a reference temperature profile. Figure 1c shows the seismogenic thickness map, using K-1 and kg/m3. In this approach, the estimates range from about 15-45 km.Figure 2 summarizes the results from the three different approaches, where the top plot presents the thermal gradient estimates, and the bottom plot shows the seismogenic thickness estimates. The left panels correspond to estimates from local flexural analysis for two different rheologies, the center panels show the geodynamic model estimates for the fully extrusive and 80% intrusive case, and the right panels are associated with the estimates from mantle density anomalies. For the latter, the two cases shown correspond to end-members parameters associated with maximum variability (density anomalies are modeled as a thin mass-sheet and K-1) and minimum variability (density anomalies assumed to be radially constant throughout the mantle and thermal expansivity of K-1) of seismogenic thickness estimates.From the observational constraints and the highly intrusive model scenario we find that the seismogenic thickness of Venus ranges from about 4 to 40 km. The constraints from flexural analysis are related to the largest thermal gradient estimated (and thinnest seismogenic zones). This is likely because many of the investigated features are associated with locally anomalous temperatures, probably associated with magmatic processes [10]. It is also important to note that the thermal gradient estimates correspond to the time of formation of the features and it is possible that the thermal gradients are not as high at present day. Interestingly, the high intrusive geodynamic model also reaches high thermal gradient values (above 20 K/km) locally where there has been recent emplacement of intrusive melts (see Herrera et al., this meeting, for more details). Nevertheless, our results indicate that the background thermal gradient of Venus ranges from 5-10 K/km which is associated with seismogenic thicknesses of roughly 10-30 km.References:[1] Foster and Nimmo 1996, EPSL [2] Billoti and Suppe 1999, Icarus[3] Davaille et al. 2017, Nature Geoscience [4] Smrekar et al. 2010, Science [5] Herrick and Hensley 2023, Science [7] O’Rourke and Smrekar 2018, JGR: Planets [8] Borrelli et al. 2021, JGR: Planets [9] Maia and Wieczorek 2022, JGR: Planets [10] Smrekar et al. 2023, Nature Geoscience [11] Mackwell et al 1998, JGR [12] Plesa et al. 2023, EGU [13] Maia et al. 2023 GRL

Lunar lava tubes are of significant interest for potential human exploration of the Moon, therefore it is important to study their subsurface extent and physical properties in detail. The underground existence of the lava tubes in the mare regions due to past volcanic activity has been predicted in the past (e.g. [1,2]) and orbiting missions for gravity surveys (GRAIL) and radar investigations (Lunar Radar Sounder onboard SELENE) have identified candidate locations of these subsurface structures (e.g. [3-5]). But only global constraints could be inferred, because the spatial resolution achievable from orbit is not sufficient compared to the estimated extents of the lava caves. To better understand the real extent and depth of the lava tubes, measurements on the lunar surface have to be performed. In this study we propose surface microgravity survey techniques to measure gravitational anomalies. A gravimeter experiment on a lunar rover would map out the spatial variation of the surface gravity and constrain subsurface voids shown as mass deficits accurately when traversing a lava tube. Microgravity survey yield very high spatially resolved gravity mapping. Microgravity surveys is a geophysical mapping technique commonly used on Erath to aid the location of buried features such as faults, sinkholes, tunnels and voids associated with mines, quarries as well as lava tubes [6]. The Traverse Gravimeter Experiment (TGE) on the Apollo 17 Lunar mission, allowed to determine presence and properties of a higher density lava flow [7,8]. Microgravimeter measurements can be made across linear profiles and/or equally spaced grids at survey stations in varying increments dependent on the depth of investigation.Here, we will present the lunar microgravimetric survey concept to explore subsurface extent and physical properties of lunar lava caves. For different scenarios consisting of different depth size etc. of subsurface lava tubes, the gravitational anomalies will be calculated and the traverse gravity survey will be simulated [9]. The measurements concepts and instrument requirements will be presented. A possible application of this study is the robotic explorer concept LunarLeaper [10], recently selected from the ESA 2023 Small Missions for Exploration call for a Pre-Phase A study.These measurements are ideally supported by ground penetrating radar (GPR) measurements, a technique commonly used on Earth to map shallow subsurface structures using electromagnetic reflection waves. GPR has been successfully applied to various problems in the geological, archaeological, and engineering fields as well as on mapping of lava tubes [11-14]. This combined, non-intrusive method, can help to characterize the physical properties of the lava tubes, as for example their stability and the composition of the surrounding material. These are important considerations for future human exploration of the Moon. References: [1] Murase and McBirney, 1970, Science 167, 1491. [2] Greeley, 1971, The moon, 3, doi:10.1007/BF00561842. [3] Chappaz et al., 2017, Geophysical Research Letters, 44, doi :10.1002/2016GL071588. [4] Kaku et al., 2017, Geophysical Research Letters, 44, doi.org/10.1002/2017GL074998. [5] Zhu et al., 2024, Icarus, doi :10.1016/j.icarus.2023.115814. [6] Deroussi et al., 2009, Journal of Volcanology and Geothermal Research, 184, doi:10.1016/j.jvolgeores.2008.10.002. [7] Talwani and Kahle, 1976, NASA STIRecon Tech. Rep. A, vol. 77. [8] Urbancic et al., 2017, Journal of Geophysical Research: Planets, 122, doi:10.1002/2017JE005296. [9] Noeker and Karatekin, 2022, EPSC2022-361, Europlanet Science Congress. [10] Mittelholz et al., 2024, EGU General Assembly, doi:10.5194/egusphere-egu24-21578 [11] Esmaeili et al., 2020, Journal of Geophysical Research: Planets, 125, doi:10.1029/2019JE006138. [12] Miyamoto et al., 2005, Geophysical Research Letters, 32, doi:10.1029/2005GL024159. [13] Rowell et al., 2010 CREWES Research Report, 22. [14] Gómez-Ortiz, 2014, Journal of Applied Geophysics, 109, doi:10.1016/j.jappgeo.2014.07.009.

The InSight mission is a geophysical mission aimed at better understanding the structure of Mars and of the other rocky planets of the solar system. To do so, a lander accommodating two cameras, a very sensitive seismometer, and a dynamic self-penetrating heat probe nicknamed the mole were placed on the Mars surface by the Instrument Deployment Arm (IDA). Besides geophysical data (which definitely enriched the existing knowledge on the structure of Mars), the InSight instruments significantly increased the knowledge of the geological and geotechnical characteristics of the surface material at the InSight site. Small strain (elastic) parameters were derived from wave velocity measurements during the hammering sessions between the self-penetrating probe and the seismometer. A detailed observation of the soil profile along a depth of 37 cm was made possible thanks to the photos taken by the cameras, and to a detailed analysis of the mole penetration process. Further information was provided by an intense campaign of scraping and piling conducted by the IDA on the surface sand/dust layer. It was shown that the soil profile was composed of a surface 1 cm thick sand/dust layer, overlaying an around 20 cm thick loose duricrust made up of a cohesive matrix containing some pebbles, located above a 12 cm layer of sand overlaying a gravel/sand deposit. It is believed that the geology and soil mechanics data provided by the InSight mission will help for further robotic exploration of Mars.

SUMMARY The analysis of seismic events recorded by NASA’s InSight seismometer remains challenging, given their commonly low magnitudes and large epicentral distances, and concurrently, strongly varying background noise. These factors collectively result in low signal-to-noise ratios (SNR) across most event recordings. We use a deep learning denoising approach to mitigate the noise contamination, aiming to enhance the data analysis and the seismic event catalogue. Our systematic tests demonstrate that denoising performs comparable to fine-tuned bandpass filtering at high SNRs, but clearly outperforms it at low SNRs with respect to accurate waveform and amplitude retrieval, as well as onset picking. We review the denoised waveform data of all 98 low-frequency events in the Marsquake Service catalogue version 14, and improve their location when possible through the identification of phase picks and backazimuths, while ensuring consistency with the raw data. We demonstrate that several event waveforms can be explained by marsquake doublets—two similarly strong quakes in spatio-temporal proximity that result in overlapping waveforms at InSight—and we locate them in Cerberus Fossae (CF). Additionally, we identify and investigate aftershocks and an event sequence consisting of numerous relatively high magnitude marsquakes occurring within hours at epicentral distances beyond CF. As a result of this review and interpretation, we extend the catalogue in event numbers ($+$8 per cent), in events with epicentral distances and magnitudes ($+$50 per cent), and events with backazimuths and a resulting full locations ($+$46 per cent), leading to a more comprehensive description of Martian seismicity.

Last year, the first active lava flow on Venus was discovered by Herrick & Hensley (2023), adding to the growing body of evidence that Venus is currently volcanically active with frequently erupting volcanoes (Byrne & Krishnamoorthy, 2022; Van Zelst, 2022). This discovery immediately begged the question as to whether Venus is seismically active at present as well. Indeed, more and more theoretical studies show that Venus could be seismically active today (Van Zelst et al., 2024). In the next decade, we will unravel some of Venus' secrets through a multitude of Venus-bound missions, but determining the seismic activity of the planet is not one of their main goals. Missions to Mars and the Moon have shown the wealth of information that can be gleaned from seismic studies of a planet. We argue here that the seismological exploration of Venus — ‘the quest for quakes on Venus' — should be the next priority of space agencies. We first estimate upper and lower bounds on the expected annual seismicity of Venus by scaling the seismicity of the Earth. We consider different scaling factors for different tectonic settings and account for the lower seismogenic zone thickness of Venus. We find that 95 — 296 venusquakes equal to or larger than moment magnitude (Mw) 4 per year are expected for an inactive Venus, where the global seismicity rate is assumed to be similar to that of continental intraplate seismicity on Earth. For the active Venus scenarios, we assume that the coronae, fold belts, and rifts of Venus are currently seismically active. This results in 1,161 — 3,609 venusquakes equal to or larger than Mw 4 annually as a realistic lower bound and 5,715 — 17,773 venusquakes equal to or larger than Mw 4 per year as a maximum upper bound for an active Venus. To assess whether any quakes could occur at all at Venus’ high temperatures, we estimate the seismogenic thickness of the planet in three independent ways: through estimates from flexure, through geodynamic models, and through estimates from mantle density anomalies. For all these estimates, we look at the depths of the 600°C and 800°C isotherms as the maximum limit of brittle failure and hence the maximum depth of the seismogenic zone. The seismogenic thickness estimates we find show a large range depending on the assumptions we make for each different method, but in general show that the seismogenic thickness on Venus is on average approximately 10 to 35 km globally. To learn more about venusquakes and deduce the interior structure of Venus from them, the detection of seismic waves is crucial. Various concepts to measure seismic waves on Venus have already been explored in the past decades. These detection methods include typical geophysical ground sensors already deployed on Earth, the Moon, and Mars; pressure sensors on balloons; and airglow imagers on orbiters to detect ground motion, the infrasound signals generated by seismic waves, and the corresponding airglow variations in the upper atmosphere. Here, we provide a first comparison between the detection capabilities of these different measurement techniques and our estimates of Venus' seismic activity. In addition, we discuss the performance requirements and measurement durations required to detect seismic waves with the various detection methods. We also briefly suggest target regions with a high likelihood of significant surface deformation and/or seismicity for current and future missions. These targets are particularly useful for the upcoming VERITAS (Venus Emissivity, Radio Science, InSAR, Topography and Spectroscopy) and EnVision missions. They would specifically benefit from the repeat pass interferometry of VERITAS, which detects surface deformation and can therefore in principle constrain the maximum displacement of surface faulting at locations that are visited twice during the mission.Our extensive study into the potential seismicity of Venus could be used to drive the design of future mission concepts aiming to study the seismicity of Venus.References Byrne, P. K., & Krishnamoorthy, S. (2022). Estimates on the frequency of volcanic eruptions on Venus. Journal of Geophysical Research: Planets, 127(1), e2021JE007040. Herrick, R. R., & Hensley, S. (2023). Surface changes observed on a Venusian volcano during the Magellan mission. Science, 379(6638), 1205-1208. Van Zelst, I. (2022). Comment on “Estimates on the Frequency of Volcanic Eruptions on Venus” by Byrne and Krishnamoorthy (2022). Journal of Geophysical Research: Planets, 127(12), e2022JE007448. Van Zelst, I., Maia, J., Plesa, A.-C., Ghail, R. C., Spühler, M. (2024). Estimates on the possible annual seismicity of Venus. EarthArxiv, 10.31223/X5DQ0C