Wind measurements from landed missions on Mars are vital to characterize the near surface atmospheric behavior on Mars and improve atmospheric models. These winds are responsible for aeolian change and the mixing of dust in and out of the atmosphere, which has a significant effect on global circulation. The NASA InSight mission recorded wind data for around 750 sols. The seismometer, however, recorded data for around 1400 sols. The dominant source of energy in the seismic data is in fact due to winds. To this end, we propose a machine learning model, dubbed WindSightNet, to map the seismic data to wind speed and direction. The trained network achieves wind speed and direction measurements with errors of 0.932 m/s and 32.6 degrees. We use WindSightNet to retrieve winds from the entire time the seismometer was recording to compare year-to-year wind variations at InSight. The continuous nature of the data set enables the extraction of periodic behavior. We observe a pattern of waves due to baroclinic activity with periods of similar to ${\sim} $2-3, similar to ${\sim} $4, similar to ${\sim} $5-7 and similar to ${\sim} $9-20 sols occurring Ls= ${L}_{s}=$180-360 degrees. We also observe periodicity during the day due to convective cells. This is used to estimate the boundary layer height, yielding values between 2.3 and 7.7 km. A data-science based metric is proposed to provide a quantification of the year-to-year differences in the wind speeds. This highlights variations linked to dust activity as well as other transient differences. On the whole, the seismic-derived winds confirm the dominance of the global circulation leading to repeatable weather patterns.

The seismometer of the InSight NASA discovery mission recorded more than 1,300 seismic events on Mars, grouped into different families according to their frequency content. Here, we present a method to detect quake nests based on time domain correlation of long‐duration waveforms (520 s). Event doublet candidates are first detected on the 2.4 Hz local resonance, and then validated by simultaneous detections on different components and different frequency bands. We provide a detailed analysis of the impact of noise on these detections. Our method revealed a triplet of very high frequency events (S0334b/S0334c/S0343a). These observations demonstrate that quake nests do occur on Mars, validating an active seismic area at 26° epicentral distance, which is interpreted as Cerberus Fossae, and that both impacts and quakes generate the very high frequency‐type seismic events. These repeating waveforms could be used to test noise removal methods applied to InSight seismic data.

This work introduces a comprehensive model of sound propagation on Mars, in light of the recent operation of several microphones on the Martian surface. The main outcome of this work is an operational acoustic model capable of simulating the sound field created by any source, at any location on the Martian surface, at any time. Expanding on the result of previous work (Gillier et al., 2024, ), we use the parabolic equation method for sound propagation in order to obtain the overall sound field produced by a source, in a given atmospheric composition and state, and accounting for ground properties. The resulting model enables the study of acoustics on Mars, and has the potential also to be used to probe the properties of the Martian environment using acoustic measurements with known sources. We investigate the effects of the Martian ground and the vertical profile of temperature and wind, on sound propagation. We find that the ground has a minor effect on sound propagation, and the wind profile strongly influences sound propagation as on Earth. However, the midday near surface temperature profiles on Mars are shown to cause refraction, which generates non-negligible acoustic losses that are an order of magnitude stronger than typical refraction-related acoustic losses on Earth. We show that the effect of the Martian atmospheric turbulence is to slightly reduce the acoustic losses due to refraction. Finally, we apply our model to show that refraction and atmospheric turbulence have a negligible effect on the propagation of sound from Ingenuity to the Perseverance rover. Sound provides new ways for exploring the Martian environment. Whether to examine the characteristics of sound sources on Mars or to infer atmospheric properties from the behavior of sound waves in the Martian atmosphere, an accurate model of sound propagation on Mars is needed. This model must account for the path traveled by the sound waves in the atmosphere as well as their interactions with the planet's surface. We propose a model that allows us to compute the sound that would be received by a microphone depending on its relative position to a source given a set of atmospheric conditions. We investigate the effects of the ground, the vertical gradient of temperature and the wind speed, as well as the effects of atmospheric turbulence. We find that, because of the strong temperature gradient at noon on Mars, sound is bent upwards creating a quieter zone close to the ground. This effect also occurs on Earth, but is much stronger on Mars. The main outcome of this work is a model that can simulate the sound field created by any source for any location at the Martian surface at any time of year and any time of day. We have developed a model to compute the sound field created by a specific sound source at any time and place near the Martian surface Model predictions show that the main parameters affecting sound propagation are the temperature and wind speed profiles Refraction and atmospheric turbulence have a small effect on acoustic waves at the altitude of the Ingenuity rotorcraft

This work introduces a comprehensive model of sound attenuation and speed on Mars, in light of the recent operation of several microphones on the surface of Mars. The proposed acoustic model calculates the sound speed and attenuation throughout the near-surface Martian atmosphere based on first-principles. We evaluate the effects of the seasonal and diurnal cycle of air temperature, pressure and CO2, as well as the concentration of airborne dust on the sound attenuation. The attenuation and speed of sound are most sensitive to the air temperature and, therefore, they vary with the diurnal temperature cycle and to a lesser degree with the seasonal changes in temperature. The speed of sound also varies with the seasonal variations of the concentration of CO2. The main outcome of this work is an acoustic model capable of computing the sound speed and attenuation for any location at the Martian surface at any time of year and any time of day. Sound offers new means of investigating the Martian environment. To study the properties of sound sources on Mars, or to derive atmospheric properties from the way sound travels in the Martian atmosphere, a model of the sound attenuation and speed on Mars is needed. In this paper, we propose such a model that allows the sound attenuation and speed at the Martian surface to be computed at any point and time. We investigate how these two properties change with air temperature, pressure, the chemical composition of the Martian atmosphere, the concentration of airborne dust, and with time of day and season. This paints the picture of Mars as a very contrasting planet acoustically, with a very wide range of attenuation and speed of sound compared to Earth because of the daily variations of temperature and the yearly variations of pressure and chemical composition. Attenuation and speed of sound are modeled at every point of the Martian surface Sound attenuation and speed are most affected by the variation of pressure and temperature associated with the diurnal and seasonal cycles The variations of sound attenuation and speed during a given day are very strong compared to Earth

The Perseverance rover is carrying out an original acoustic experiment on Mars: the SuperCam microphone records the spherical acoustic waves generated by laser sparks at distances from 2 m to more than 8 m. These N-shaped acoustic waves scatter from the multiple local heterogeneities of the turbulent atmosphere. Therefore, large and random fluctuations of sound travel time and intensity develop as the waves cross the medium. The variances of the travel times and the scintillation index (normalized variance of the sound intensity) are studied within the mathematical formalism of the propagation of spherical acoustic waves through thermal turbulence to infer statistical properties of the Mars atmospheric temperature fluctuation field. The comparison with the theory is made by simplifying assumptions that do not include wind fluctuations and diffraction effects. Two Earth years (about one Martian year) of observations acquired during the maximum convective period (10:00-14:00 Mars local time) show a good agreement between the dataset and the formalism: the travel time variance diverges from the linear Chernov solution exactly where the density of occurrence of the first caustic reaches its maximum. Moreover, on average, waves travel faster than the mean speed of sound due to a fast path effect, which is also observed on Earth. To account for the distribution of turbulent eddies, several power spectra are tested and the best match to observation is obtained with a generalized von Karman spectrum with a shallower slope than the Kolmogorov cascade, phi(k) proportional to (1+k(2)L(2))(-4/3). It is associated with an outer scale of turbulence, L, of 11 cm at 2 m above the surface and a standard deviation of 6 K over 9 s for the temperature. These near-surface atmospheric properties are consistent with a weak to moderate wave scattering regime around noon with little saturation. Overall, this study presents an innovative and promising methodology to probe the near-surface atmospheric turbulence on Mars.

We investigate the vortex and dust devil activity on Jezero crater over more than one and half Martian years of meteorological data acquired by the MEDA sensors on the Mars 2020 Perseverance rover. During the initial phase of the M2020 mission (sols 15-415, Ls=152º-156º, Martian Year 36, MY36) Perseverance observed a strong vortex activity with a high frequency of dust devils (Newman et al. Science Advances, 2022; Hueso et al. JGR: Planets, 2023). However, later activity over Martian Autumn-Winter (MY36) showed a strong decrease in the frequency and intensity of vortices and dust devils that continued in Spring MY37 when Perseverance was close to the crater rim. Later data acquired over Summer MY37 shows a comparable level of activity than the previous Martian year. In this work, we explore how the combination of changes in the surface properties of the terrain, and the influence of the topography over more than 24 km of terrain traversed, are needed to explain the different levels of activity observed in similar seasons. The lack of accurate wind data after sol 315, when the wind sensors started to operate with some limitations (Viudez-Moreiras et al., 2022), does not allow us at present to model accurately vortex sizes and their distance from MEDA after that sol. We explore how the combined measurements from the pressure sensor (PS), the Atmospheric Temperature Sensors (ATS), and the Remote Dust Sensors (RDS) constraining the geometry of encounters with Dust Devils, give us information about the thermodynamics of the vortices. This analysis is done for a small selection of vortices where the combination of PS-ATS and RDS data shows a consistent geometry of the vortex encounter that validates the temperature enhancements observed during the vortex encounters.

IntroductionThe two microphones onboard the Perseverance rover have now been operating for more than three years on the surface of Mars. They have provided the first sound recordings at the Martian surface and the most extensive acoustic dataset recorded on another planet. The Martian microphones have recorded sound waves, and more generally signals, from a wide variety of sources. Given the novelty of this dataset, we felt the need for a catalogue of Martian sounds. This catalogue contains a description of every type of sound both from an individual and a statistical perspective. This allows us to highlight the particular characteristics of each of the sources that can be retrieved from recording their sounds, including possible variations over time for recurring recordings. Using this catalogue, we also discuss scientific applications for each of the sound sources, highlighting how useful microphone data are to survey the Martian environment. Finally, the catalogue serves as a starting point for newcomers by demonstrating how to use the acoustic data and explaining which features of the recordings are already well understood and identifying others that are still open to investigation.The Martian microphonesTwo microphones are operated onboard the Perseverance rover. The SuperCam Microphone [1], located on the mast unit, operates in two modes, the MIC only mode where up to 167 s of sound at 25 kHz can be recorded, and the MIC+LIBS mode that record the shots of the LIBS instrument. More than 24 hours of recording have been acquired in the first mode and more than 6000 LIBS sequences have been recorded in the second one. The EDLCam microphone [2], located on the side of the rover body, can record for longer period of times at 48 kHz. More than 12 hours of recordings, mainly rover sound, have been acquired.Both microphones are subject to operational constraints that shape the resulting dataset.Environment sound sourcesWhile not being strictly speaking a sound, the signal coming from the interaction between the wind and the microphone is always present on the recording at different levels. This allows the microphone to act as a high frequency wind sensor [3]. The spectra of the wind recording contain information about atmospheric turbulence near the Martian surface [4], which can be studied at different times of year and day thanks to the regular coverage offered by the microphone’s dataset.The microphone-derived wind signal has been used to resolve the properties of a dust devil that was recorded during a rare direct encounter with the rover. During this event [5] the sound of the dust grains carried by the vortex impacting on the rover were also recorded, allowing an estimation of their number density.Artificial sound sourcesSound recording around every LIBS shot contains information about the sound wave travel times and energy that can be used to study the temperature fluctuation [6] and the atmospheric turbulence [7]. This is made possible through the speed of sound and the scintillation measurements at different times of year thanks to the almost daily coverage in LIBS sound recording. Other artificial sounds such as the Ingenuity helicopter [8] or the operation of different parts of the rover (driving, drilling, abrading, MOXIE compressor [9], pumping of the heat rejection system fluid) were also recorded. These data were used to study the acoustic properties of the Martian atmosphere [10] and to monitor the health of the rover systems.ConclusionAfter three years at the Martian surface, Perseverance has sent back to Earth a rich dataset of acoustic recordings that has already yielded numerous scientific results. As it continues its journey at the surface of Mars, we expect that the microphones will bring greater detail to the established results as well as leading to new discoveries. Moreover, lessons learned on this mission will be useful for future acoustic experiments on other planetary bodies [11, 12]. [1] Mimoun et al. (2023) Space Science Reviews, 219 [2] Maki et al. (2020) Space Science Reviews [3] Stott et al. (2023) JGR : Planets [4] Stott et al. (2024) 10th International Mars Conference [5] Murdoch et al. (2022) Nat. Commun. [6] Chide et al. (2022) GRL [7] Chide et al. (2024) J. Acoust. Soc. Am. 155, 420–435. [8] Lorenz et al. (2023) Planetary and Space Sciences 230. [9] Hecht et al. (2021) Space Science Review [10] Chide et al. (2023) Earth and Planetary Science Letters 615 [11] Barnes et al. (2021) The Planetary Science Journal,2,4 [12] Gillier et al. (2024) IPPW

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.

AbstractOn 19 February 2021 the SuperCam microphone onboard Perseverance recorded the first ever sounds on the surface of Mars. These recordings of the Martian dynamic pressure fluctuations actually contain a wealth of information about the Martian atmosphere.IntroductionThe Mars 2020 Perseverance rover [1] landed in Jezeero crater on 18 February 2021. The SuperCam Microphone is located at a height of 2.1 m above the ground on the front of the SuperCam instrument (Fig 1; [2,3]). Although the primary science objective of the SuperCam Microphone is to support the SuperCam Laser-Induced Breakdown Spectroscopy (LIBS) investigations by providing additional information about the physical properties of the LIBS targets [4,5], the microphone also has the capacity to provide data for new and important atmospheric investigations. With a bandwidth from 100 Hz to 10 kHz, the overarching atmospheric science goal of the microphone is to characterise the Martian atmospheric dynamics at high frequency, including the diurnal and seasonal evolution. Figure 1: The SuperCam instrument, including the microphone, on the surface of Mars Studying the turbulent Martian atmosphere with the SuperCam microphonePressure fluctuations in the atmosphere tell us about boundary layer convection, convective cells and vortices, and the inertial and dissipative regimes. Compared with Earth, Martian daytime turbulence is characterised by a stronger radiative control, a lack of latent heat forcing and a reduced inertial range [6].Wind gustiness, convective vortex activity and the spectral slope of pressure, wind and temperature measurements can be used as indicators of turbulent motion in the atmosphere. These variables exhibit strong diurnal and seasonal variations (e.g., [7-10]). Recent analyses have also shown that wind gustiness on Mars is positively correlated to surface temperature rather than ambient wind speed and sensible heat flux [10].Previous Martian space missions have provided valuable pressure, wind and temperature data allowing the Martian turbulence to be studied (e.g., [7,11]). The highest frequency atmospheric measurements that we currently have come from the pressure sensor on the InSight mission [12,13]. The InSight pressure measurements show unexpected behaviour. For example, they seem to contradict the theoretical predictions (Kolmogorov theory) for the cascade of the inertial range [14].With its high sampling frequency, we can use the SuperCam microphone to study Martian turbulence on new, previously inaccessible, scales. From recordings at different local times and over different seasons, the SuperCam microphone can complement the lower frequency MEDA [15] wind speed measurements and provide a window into previously unexplored regimes of Martian atmospheric science.The SuperCam microphone as a high frequency wind sensorPre-mission, in wind tunnel tests, it has been shown that the microphone can be used to estimate the wind speed – a quadratic relationship exists between wind speed and the microphone RMS signal [16]. However, the relationship between the microphone signal and wind speed may be more complex than this simple relationship, and other atmospheric effects (such as atmospheric stability) should also be included in the future.The dynamic pressure signal measured by the microphone is a combination of the atmospheric dynamic pressure fluctuations and the aeroacoustic fluctuations due to vortex shedding (Fig. 2; [16,17]). Simultaneous MEDA and SuperCam measurements (over 360°) are necessary in order to perform a cross-calibration activity with MEDA in order to produce absolute wind speed estimates. The microphone can also be used with single (not directional) observations to provide relative wind speed estimates, and to study the gustiness in the Martian atmosphere [18]. Figure 2: CFD simulations of vortex shedding around the SuperCam instrument under Martian atmospheric conditions with a wind speed of 5 m/s from the right of this image. The microphone is indicated by the small red sphere on the front of the instrument [16,17]. The blue and dark green areas correspond to the vortices generated around, and in the wake of, the SuperCam instrument Air temperature measurements with the SuperCam microphoneCombined LIBS and SuperCam microphone operations [4, 19 - 20] can be used to probe the high frequency temperature fluctuations in the Martian atmosphere. Specifically, measuring the propagation time of the acoustic signal produced by the laser gives the sound speed from the ground to the microphone. The sound speed can then be used to derive the ‘acoustic temperature’ - the average of the air temperature over the 2 meters between the microphone and the laser target - for every laser shot (3 Hz). This is potentially important because large thermal gradients just above the Mars surface have been hinted at in previous data [21].ConclusionsThe SuperCam microphone observations allow us to quantify the dynamic pressure spectra, the wind gustiness and the air temperature at high frequency thus providing an opportunity to characterise the Martian atmospheric dynamics in previously unexplored regimes. The SuperCam microphone may also be used for more opportunistic science such as searching for the acoustic signals of convective vortices [22].References[1] Farley et al. SSR 2020. [2] Maurice et al. SSR 2021. [3] Wiens et al., SSR 2021. [4] Murdoch et al. PSS 2019. [5] Chide et al. SAB 2019. [6] Spiga et al., SSR 2019. [7] Davy et al., JGR, 2010. [8] Murdoch et al., SSR 2017. [9] Ullan et al. Icarus 2017. [10] Spiga et al. JGR-Planets 2020. [11] Larsen et al. BLM 2002. [12] Banfield et al. SSR 2019. [13] Banerdt et al. Nature Geoscience 2020. [14] Banfield, Spiga et al. Nature Geoscience 2020. [15] Rodriguez-Manfredi et al. SSR 2021. [16] Chide et al. Icarus 2021. [17] Bury et al. EPSC 2019. [18] Stott et al. EPSC 2021. [19] Chide et al. SAB 2020. [20] Chide et al. EPSC 2021. [21] Schofield et al. Science 1997. [22] Murdoch et al. LPSC 202

Atmospheric turbulence, irregular fluctuations of the fluid state, is studied on Mars. Universality of the turbulence spectrum underpins atmospheric models where computational requirements preclude full fidelity simulations of the smallest scales. However, there are discrepancies among reports on the existence and spectral location of universal scaling in Martian atmospheric data. Here, results indicate the smallest resolvable structures from Martian wind speed data are still associated with the energetic regime, which may ultimately explain why multiple reports have not found a consistent Kolmogorov-like spectral regime on Mars. Universal spectral scaling of wind data from Perseverance’s Mars Environmental Dynamics Analyzer is used to estimate the thresholds that separate three turbulence regimes: energetic, inertial, and molecular dissipation. Wind measurements at 2-Hz, the fastest sampling rate for direct wind sensor measurements on Mars, resolves turbulence in the energetic regime and approaches the inertial regime, which is consistent with reported Martian dust devil sizes. Editor’s Summary: Observations of turbulence scaling in the Martian atmosphere are limited by the sampling frequency of current apparatus, which could explain discrepancies in previous results, suggests an analysis of data from the Mars Environmental Dynamics Analyzer.

AbstractThe SuperCam instrument on the NASA Perseverance rover [1,2] is equipped with a microphone which, for the first time, has recorded sounds from Mars. These sounds include shockwaves from the laser-induce breakdown spectroscopy technique, the Ingenuity rotorcraft and the ambient Martian atmosphere [3,4]. Each of these offers a unique dataset to study Martian atmospheric dynamics at high frequencies. In this abstract we present preliminary results on studying the relationship between the wind and the sounds recorded from the microphone.1. The SuperCam microphoneThe microphone is a Knowles Electret condenser microphone model EK-23132 [1,2,5]. It can record at sampling rates of 25kHz or 100kHz for up to 167s. The nominal bandwidth is 100Hz-10kHz but lower frequencies can be retrieved. It is located on the SuperCam mast unit 2.1m above the ground and is aligned with the camera. This means that the microphone can be made to point in different azimuths and elevations.2. Wind speed estimation from the microphoneThe microphone records the atmospheric pressure at high frequencies. This dynamic pressure is linked to the winds on Mars [5,6]. In a pre-landing analogue study in a wind tunnel, Chide et al. 2021 [5] found that the root mean square (RMS) of the pressure signal is correlated to the wind speed. It was shown that the RMS value from the microphone in the bandwidth of 100-500Hz is proportional to the square of the wind speed. This frequency band was seen to not be extremely sensitive to the wind incidence azimuth but there is some uncertainty, especially for higher wind speeds.We can calculate the RMS envelope over the recording. The square root of this envelope is then proportional to wind speed and can be used as a relative estimate. Figure 1 shows initial results from an afternoon recording on Sol 38 of the mission.Figure 1: Microphone data from Sol 38. Top panel: microphone signal, Middle panel: spectrogram of microphone data, Bottom panel: square root of RMS envelope for 100-500Hz bandwidth.A cross-calibration will be performed with the Mars environmental dynamic analyser (MEDA) wind sensor [7]. This will enable us to obtain an absolute wind speed determination with the microphone. The mast will also be rotated during the cross-calibration to help capture recordings for a variety of wind speed incidence azimuths and thus also determine the sensitivity to wind direction including the identification of vortex shedding [5]. Moreover, a variation of the mast elevation may lead to the determination of vertical wind speeds.The relationship could also be sensitive to other effects, such as the atmospheric stability. To this end, we aim to track diurnal and seasonal variation, along with temperature and static pressure conditions.3. Wind speed variation - gustinessThe microphone recordings yield an estimate of the Martian wind speed. The so far obtained relative wind speed estimates can be used for an analysis of the wind gustiness, that is, the wind speed variation with respect to its mean. This has been explored for Phoenix, Viking and InSight data [6,8] with a gustiness metric defined as the wind speed standard deviation, σw, over the mean wind speed, μw, asnormalised gustiness = σw/μw.The gustiness metric was applied to several microphone recordings around Noon and 16:00 local true solar time (LTST). These results indicate that the later afternoons are more turbulent than midday, where some acquisitions contain very little wind. However, the noon recordings can contain infrequent very large gusts, including the largest so far observed by the microphone. This information was utilised early on in the mission to aid the understanding of potential flight conditions for the rotorcraft Ingenuity.4. ConclusionsWe have introduced how the microphone data are related to the Martian wind. It enables an estimation of the Martian wind speed and the ability to examine the high frequency content of wind gusts. This is important for the understanding of the dynamic pressure spectrum on Mars [3]. The microphone will record the high frequency portion of this dynamic pressure spectrum shedding light on the dissipative regime in Martian turbulence. The variability of the relationship to wind speed and the distribution of gustiness provides a study of high frequency Martian atmospheric dynamics, valuable for studying the Martian planetary boundary layer (PBL). References[1] Wiens et al., SSR, 2021;[2] Maurice et al., SSR, 2021;[3] Murdoch et al., EPSC, 2021[4] Chide et al., EPSC, 2021;[5] Chide et al., ICARUS, 2021;[6] Murdoch et al., SSR, 2017;[7] Rodriguez-Manfredi et al., SSR, 2021;[8] Spiga et al., JGR, 202

Abstract:The Mars 2020 Perseverance rover, which landed in February 2021, is carrying the SuperCam remote sensing suite [1,2]. It is a multifunctional spectroscopy instrument to analyze Martian rocks and soils with Laser-Induced Breakdown Spectroscopy (LIBS), time resolved Raman and luminescence, Visible and Infrared Reflectance Spectroscopy, and color context imaging. It also includes a microphone (see Fig. 1) that records acoustic pressure fluctuations in the 100 Hz to 10 kHz frequency bandwidth. In particular, it supports LIBS investigation by listening to laser-induced sparks caused by the supersonic expansion of the plasma plume [3, 4]. The microphone also contributes to atmospheric science by recording the ambient noise [wind, turbulence, 5, 6] and it already listened to unique sounds from the Ingenuity Mars Helicopter flights. This abstract focuses on the first analysis of the LIBS acoustic signal recorded on Martian targets near the Octavia E. Butler landing site of Perseverance.Figure 1 - WATSON image of the upper part of the Perseverance Remote Sensing Mast. The microphone is seen in the red rectangle. Credits: NASA/JPL-Caltech/MSSS/ASUListening to laser-induced sparks on Mars:The LIBS experiment of Supercam uses a pulsed laser in the infrared (1064nm) to ablate rock or soil targets at the Mars surface at distance up to 7 meters. A standard LIBS burst consists of 30 laser shots repeated at the same location on a target. It creates an ablation pit up to hundreds of µm deep, depending on the target hardness (see LIBS pits in Fig. 2) [4, 7]. Longer bursts of 150 shots, called depth profiles, can also be performed to look for any chemical stratification with depth.Figure 2 - Hedgehog target (sol 37) sampled by LIBS (10 points of 30 shots each). (a) Mastcam-Z documentation image. (b) RMI context mosaic highlighting the LIBS pits.Credits: NASA/JPL-Caltech/ASU/MSSS and NASA/JPL-Caltech/LANL/CNES/IRAPIt has been shown in lab studies [3, 4] that recording of the LIBS acoustic signal helps to determine the target physical properties (hardness) and also the laser pit volume by looking at the decrease of the signal amplitude with the number of laser shots performed at the same location. In addition, laser sparks may also be used to study rock coatings. In particular, it will help to determine the depth of the transition between a coating and its underlying host rock [8].Moreover, as the start of the microphone recording is triggered on the laser pulse, the propagation time of the sound wave from the ground up to the microphone height is precisely measured. Therefore, it gives the sound speed along the sound propagation path. This parameter is used to estimate the ‘acoustic temperature’, an average of the air temperature over the two first meters from the ground [9]. First results on Martian targets:Up to sol 78 of the mission, the Supercam microphone has recorded the LIBS acoustic signal from 12 targets, including 3 soil targets and 2 depth profiles.The LIBS acoustic signal recorded on the float rock Hedgehog (sol 37) is represented in Fig. 3. The time series (Fig. 3a) shows a shot-to-shot decrease of the acoustic amplitude over the 30 shots fired in this target. The comparison with the hardness calibration curve presented in [4] suggests a soft target with a Vickers hardness lower than 10 and an ablated volume of about 200 µm. The frequency spectrum (Fig. 3b) is showing an acoustic bandwidth between 2 kHz and 10 kHz (see Fig. 3a), consistent with pre-flight calibrations [10]. Some gaps in the spectrum (5700 Hz, 10900 Hz, 14800 Hz) are indicative of destructive interferences induced by the reflection of the sound wave over the structure of the mast. Some wind-induced signal are also noticed in the time series (see red circles in Fig. 3a). They can be easily filtered, as their frequency content is lower than 500 Hz [6]. However, the influence of the turbulent atmosphere on the LIBS acoustic signal, needs to be assessed, as it was not tested in the laboratory.Figure 3 - Time series (a) and power spectral density (b) of the LIBS acoustic signal recorded on point #5 of the Hedgehog target (sol 37)As for the soil targets, the LIBS acoustic data show a clear decrease with increasing shot number due to shielding within the self-induced hole and also helps to determine whether the laser hit a coarse grain (louder sound) or fine-grained soil.Perspectives:The Supercam microphone has the unique capability to record the acoustic signal induced by the laser-induced plasma. The microphone will help to document the target hardness along the rover traverse and complement the chemical information provided by LIBS by adding an estimation of the ablated depth. This presentation will review results from all the microphone targets observed at the time of the conference.References[1] Wiens R. C et al., SSR 2021 https://doi.org/10.1007/s11214-020-00777-5 [2] Maurice S. et al., SSR 2021, https://doi.org/10.1007/s11214-021-00807-w [3] Chide B. et al, SAB 2019, https://doi.org/10.1016/j.sab.2019.01.008, [4] Chide B et al., SAB 2020 https://doi.org/10.1016/j.sab.2020.106000, 20, [5] Murdoch N. et al, this issue, [6] Stott et al., this issue, [7] Maurice S et al., JAAS 2016, doi:10.1039/c5ja00417a [8] Lanza N.L., LPSC 2020, 2807 [9] Chide B. et al., LPSC 2020 1366, [10] Murdoch N. 2019 PSS doi:10.1016/j.pss.2018.09.009.

Mimoun et al. (Space Sci Rev 211(1–4):383–428, 2017) developed a pre-landing noise model of the Martian seismometer package SEIS onboard InSight that analysed all the external and internal noise sources. We updated the environmental and instrumental parameters of the model as well as the ground properties with InSight mission data. We compared the output of the in situ noise model to the actual noise measured during the full mission for each individual noise source as well as for the full noise model. We evaluate in detail the efficiency of the model to fit the measured data and discuss the transient noise and other sources that were not included in the model. The main noise sources in the seismic bandwidth are the pressure noise and the lander noise, which is increased from the pre-landing model and overestimated when compared to the data; the magnetic field noise was overestimated in the pre-landing model and is now found to be negligible. The conclusions and models from this study could benefit future space missions.

Introduction:The winds are an important dynamic for Mars, changing the surface of the planet to this day. These wind flows are often turbulent, either convective during the day or more shear flows from topographically induced instabilities. This turbulent variation represents one of the fastest changing dynamics taking place on Mars. As a result, its full characterisation is of interest. Here, we will show the use of the microphone data collected by the Perseverance mission to inform on the highest frequencies of turbulence [1,2]. First, we will present the characteristics of wind speed time series inferred from the SuperCam microphone through a machine learning model developed in [3]. This highlights a range of gust timescales from 1-10s as well as both isolated gusts (perhaps due to intermittent turbulence) and also consistently gusty periods. Next, we demonstrate that the microphone spectra can be used to analyse the dissipative regime of turbulence on Mars. This is at the highest frequencies where the energy is removed through viscous forces. This provides an estimate of the Kolmogorov lengthscale and dissipation rate on Mars, as well as friction velocity, useful for model comparisons.The microphone signal:A dedicated campaign was performed on Mars to record background, ambient, winds with the microphone across different times of sol without the influence of acoustic sources from the rover. These recordings are each 167 s long and recorded at 25k samples per second [1]. This high sampling rate means that the microphone spectra cover the highest frequencies of turbulent fluctuations, at the dissipation regime where the energy is dissipated by viscous forces [2]. On Mars, dissipation is expected to occur at lower frequencies than on Earth. We use the microphone data to quantify the behaviour at the transition between the inertial and dissipative regime.In an outdoor environment, the dominant mechanism for generating wind noise on microphone data is through the stagnation pressure [4,5]. This is the pressure fluctuations induced by the microphone blocking a wind flow. This is in agreement with the observations by the SuperCam microphone on Mars [3]. The resulting sensitivity of the microphone data to the wind was used to extract estimates of wind speed at high frequencies [3]. Moreover, as demonstrated in microphone wind noise models [4,5], the pressure fluctuations recorded by the microphone are a transduction of turbulent wind variations, modified by a transfer function. As a result, the spectra of the microphone data from Mars can be interpreted in terms of the turbulence spectra of the wind in the surface layer of Mars.Winds and intermittent turbulence:In [3] we proposed a machine learning (Gaussian process regression) model to extract a wind speed estimate from the microphone data. These wind speeds were shown to be suitable to examine turbulent intensity, and shown gusting characteristics ranging from 1-10s. This highlights that the wind gust characteristics change. The behaviour of the gusting can be due to the intermittency of the turbulence, whether the wind flow has entered a regime of consistent turbulence or whether it is more sporadic [6]. Subsequently, the Perseverance rover has moved over a wider range of topography driving up to the rim of Jezero crater. The statistical assessment of the microphone data over this time can be used to aid the meteorological data studies from the dedicated MEDA (Mars environmental dynamics analyser) pressure and temperature sensors onboard Perseverance.Figure 1: (Left) Transfer function corrrected spectrum for a microphone recording on Mars. (Right top) Sound pressure level from microphone recording. (Right bottom) wind speed estimate from microphone recording using method in [3].Turbulent spectra: Spectra of wind flows are commonly used to describe turbulent behaviour. Energy is injected at large scales in the source region before cascading to smaller scale eddies in the inertial regime. Classically this inertial regime is characterized by the Kolmogorov power law of -5/3. However, this requires the measurement in an isotropic flow and and so is difficult to identify in measurements, which are a superposition of several effects [7]. Figure 1 shows an example of a spectrum for a microphone recording during a period of consistent gusting, along with the wind speed estimate from [3]. The spectrum in Figure 1 shows a curve between two regions, which we interpret to be the transition between the inertial and dissipative regime on Mars. Calculating the corner frequency of this curve yields an estimate of the Kolmogorov lengthscale, η, which is 0.014 m for this recording. This lengthscale is calculated for recordings over the mission with good SNR, leading to values η= 0.005-0.05 m, which are close to those expected [8]. This estimate can be used to calculate values of the dissipation rate and friction velocity, without applying assumptions based on extrapolations from Earth. As such, this can be a useful tool for model parameterization.ConclusionWe present an analysis of Martian wind flows from microphone recordings by the SuperCam instrument on the Perseverance rover. As the microphone records at a high frequency (for atmospheric instruments so far operating on Mars) we use it to characterise the turbulent properties of the wind flow. This leads to information on the distribution of gusts and their intermittency, as well as the observation of turbulent energy dissipation on Mars. The microphone can also examine turbulence through the propagation of sound, as in [9,10]. Combining these results along with those from the dedicated weather station of MEDA at larger scales can help provide a detailed picture of turbulent behaviour on Mars and its relationship with dust and topography over seasons. References [1] Mimoun et al. (2023), SSR[2] Maurice et al. (2022), Nature[3] Stott et al. (2023), JGR:Planets[4] Raspet et al. (2006), JASA[5] Van den Berg et al. (2006), JASA[6] Allouche et al. (2021), Journal of the atmospheric sciences[7] Murdoch et al. (2023), PSJ[8] Petrosyan et al. (2011), Review of Geophysics[9] Chide et al, (2024) JASA[10] Gillier et al. (2024) JGR: Planets

AbstractPlanetary defense efforts rely on estimates of the mechanical properties of asteroids, which are difficult to constrain accurately from Earth. The mechanical properties of asteroid material are also important in the interpretation of the Double Asteroid Redirection Test (DART) impact. Here we perform a detailed morphological analysis of the surface boulders on Dimorphos using images, the primary data set available from the DART mission. We estimate the bulk angle of internal friction of the boulders to be 32.7 ± 2. 5° from our measurements of the roundness of the 34 best-resolved boulders ranging in size from 1.67–6.64 m. The elongated nature of the boulders around the DART impact site implies that they were likely formed through impact processing. Finally, we find striking similarities in the morphology of the boulders on Dimorphos with those on other rubble pile asteroids (Itokawa, Ryugu and Bennu). This leads to very similar internal friction angles across the four bodies and suggests that a common formation mechanism has shaped the boulders. Our results provide key inputs for understanding the DART impact and for improving our knowledge about the physical properties, the formation and the evolution of both near-Earth rubble-pile and binary asteroids.

Introduction: The tidal encounter of asteroid Apophis with the Earth in 2029 offers the ideal scenario for the first in-situ seismic investigation of an asteroid. A seismometer can be used to monitor the seismicity of Apophis due to tidal forces [1], and other natural sources such as micro-meteoroid impacts or thermal cracks; [2-4]. In addition, a seismometer can image Apophis’ sub-surface and internal structure [2] providing information about the asteroid’s physical properties that is critical for planetary defense, and for understanding the evolutionary history of asteroids. As a consequence, there is strong international support for the first seismic experiment on an asteroid.We have developed a Compact Seismometer that is designed specifically to fit inside a small asteroid surface package and function in the challenging environment of the asteroid surface. The instrument team has extensive experience in developing, testing, and operating seismic [5,6] and acoustic [7] planetary instrumentation.Scientific Objectives: The main science and technological goal of the Compact Seismometer is to perform the first ever in-situ seismic study on the surface of an asteroid. The specific compact seismometer science objectives are as follows:Threshold science objectives:(O1) Constrain the mechanical properties of the surface during landing(O2) Measure the seismic background noise on the surface of ApophisBaseline science objectives:(O3) Quantify the seismicity of Apophis in response to tidal forces(O4) Probe the subsurface and internal structure of ApophisBonus objective:(O5) Perform the first active seismic experiment on an asteroid using the OSIRIS-APEX spacecraft – surface interactionsCompact Seismometer: The instrument consists of three commercial geophones that will each measure the ground motion along one axis, and dedicated electronics (Figs 1-2). The geophones are passive, contain no active electronics and are designed to withstand extreme environments (e.g., terrestrial boreholes). The analog electronics have been carefully designed and developed to have a high sensitivity and low intrinsic noise. The instrument is currently at TRL level 4/5 (4 for the electronics, 5 for the commercial sensors), and the development schedule is compatible with RAMSES schedule. The current best estimates of the instrument mass, volume and power budgets are ~1 kg, 0.8 L and ~ 2W, respectively.Figure 1. (left) Schematic diagram of the Compact Seismometer. (right) The Compact Seismometer containing three geophones.Operational scenario: The Compact Seismometer should be deployed to the surface of Apophis prior to the asteroid’s closest encounter with the Earth. In the lead up to the perigee, periodic measurements will be made for instrument commissioning and background noise measurements. Then, from 3 hours before to 6 hours after the perigee - when tidal-induced seismic activity is expected to occur [1] - continuous monitoring should be performed. Following the close encounter further periodic measurements should be made to monitor the evolution and diurnal variations of the background noise and seismicity. If the surface package can survive long enough, the OSIRIS-APEX excavation experiment using thrusters [8] would provide a unique opportunity to perform an active seismic experiment using the Compact Seismometer.Figure 2. Possible concept of operations for the Compact Seismometer.Surface coupling and levelling: The Compact Seismometer must land on the asteroid and be in contact with the asteroid’s surface. However, the Compact Seismometer can operate in any orientation and does not require levelling. The proposed solution is to not attempt to couple to the surface; any coupling attempt will only couple the instrument to the upper layer of regolith, which itself may not be coupled to the sub-surface. If any lofting occurs, these events can be used to characterize the surface properties during the subsequent touchdown. Performance and environment testing: The expected noise level of the Compact Seismometer is

The sounds of the Ingenuity Helicopter flying in the Martian atmosphere are among the most notable recordings of the microphone on the SuperCam instrument on the Mars 2020 Perseverance Rover. Distinct acoustic signa-tures of the helicopter were recorded on the 4th, 5th, 6th, and 8th flights: prior to this, simultaneous microphone and helicopter operations had not been verified in the testbed, and generally since these early flights the heli-copter has been too far away for its emissions to be detectable given CO2 absorption in the Mars atmosphere.The detected signatures are around 84 Hz and (occasionally) at 168 Hz, at the blade crossing frequency and its first harmonic. Several higher harmonics were prominent in hover tests in short-range recordings in a test chamber on Earth; these are attenuated by CO2 absorption at the 50m-plus ranges on Mars. Doppler shift of the 84 Hz signal can be measured and is consistent with the trajectory measured with Ingenuity's navigation camera and inertial navigation unit, and documented by Perseverance's cameras.A striking feature of the sound recordings is an unanticipated deep modulation of the signals with nulls spaced by around 15-20s, superposed on the simple and expected decline in amplitude with distance. We have evaluated and rejected models of multipath sound interference as requiring implausibly strong near-surface temperature gradients. We find instead that the modulation appears to be the signature of a slight asynchrony between the rotation rates of the two coaxial rotors, such that the blade-crossing azimuth rotates slowly during flight, resulting in a 'lighthouse' sweeping of the radiated sound pattern. Analysis of blade orientations seen in the shadow of the helicopter observed in down-looking navigation images supports this model.

On top of listening to laser shots, rover sounds and the Ingenuity rotorcraft, SuperCam’s Mars microphone has recorded over 7 hours of ambient background noise on Mars. These background recordings contain signal due to the Martian wind. Through a comparison to the meteorological data recorded by the MEDA (Mars Environmental Dynamics Analyzer), we can determine the relationships between the microphone data, the wind and the atmospheric stability. Based on these relationships, we have determined a way to estimate the wind speed using the microphone through Gaussian process regression, a machine learning technique. Owing to the sampling rate of 25 000 samples per second, the microphone data can be used to examine Mars’ atmospheric dynamics at high frequencies, as yet unexplored on Mars. We will demonstrate how the wind speed estimates from the microphone provide an assessment of turbulence at fine scales, shedding light on the dissipative regime on Mars. One particularly interesting signal recorded by the microphone was a dust devil, which had fast varying winds within the walls of its vortex and signal from dust particles hitting the rover. Combining the microphone data with information from the MEDA sensors and navigation camera (Navcam) images enabled a full parameterization of this event.

Acoustics has become extraterrestrial and Mars provides a new natural laboratory for testing sound propagation models compared to those ones on Earth. Owing to the unique combination of a microphone and two sound sources, the Ingenuity helicopter and the SuperCam laser-induced sparks, the Mars 2020 Perseverance rover payload enables the in situ characterization of unique sound propagation properties of the low-pressure CO2-dominated Mars atmosphere. In this study, we show that atmospheric turbulence is responsible for a large variability in the sound amplitudes from laser-induced sparks. This variability follows the diurnal pattern of turbulence. In addition, acoustic measurements acquired over one Martian year reveal a variation of the sound intensity by a factor of 1.8 from a constant source due to the seasonal cycle of pressure and temperature that significantly modifies the acoustic impedance and shock-wave formation. Finally, we show that the evolution of the Ingenuity tones and laser spark amplitudes with distance is consistent with one of the existing sound absorption models, which is a key parameter for numerical simulations applied to geophysical experiments on CO2-rich atmospheres. Overall, these results demonstrate the potential of sound propagation to interrogate the Mars environment and will therefore help in the design of future acoustic-based experiments for Mars or other planetary atmospheres such as Venus and Titan.

We characterize vortex and dust devils (DDs) at Jezero from pressure and winds obtained with the Mars Environmental Dynamics Analyzer (MEDA) instrument on Mars 2020 over 415 Martian days (sols) ( Ls = 6°–213°). Vortices are abundant (4.9 per sol with pressure drops >0.5 Pa correcting from gaps in coverage) and they peak at noon. At least one in every five vortices carries dust, and 75% of all vortices with Δ p > 2.0 Pa are dusty. Seasonal variability was small but DDs were abundant during a dust storm ( Ls = 152°–156°). Vortices are more frequent and intense over terrains with lower thermal inertia favoring high daytime surface‐to‐air temperature gradients. We fit measurements of winds and pressure during DD encounters to models of vortices. We obtain vortex diameters that range from 5 to 135 m with a mean of 20 m, and from the frequency of close encounters we estimate a DD activity of 2.0–3.0 DDs km −2 sol −1 . A comparison of MEDA observations with a Large Eddy Simulation of Jezero at Ls = 45° produces a similar result. Three 100‐m size DDs passed within 30 m of the rover from what we estimate that the activity of DDs with diameters >100 m is 0.1 DDs km −2 sol −1 , implying that dust lifting is dominated by the largest vortices in Jezero. At least one vortex had a central pressure drop of 9.0 Pa and internal winds of 25 ms −1 . The MEDA wind sensors were partially damaged during two DD encounters whose characteristics we elaborate in detail.