Search

International audience; 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 signatures 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 helicopter has been too far away for its emissions to be detectable given CO 2 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 CO 2 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.

Convective vortices (whirlwinds) and dust devils (dust-loaded vortices) are one of the most common phenomena on Mars, observable on a daily basis. They reflect the local thermodynamical structure of the atmosphere and are the driving force of the dust cycle. Additionally, they cause an elastic ground deformation, which is useful for retrieving the subsurface rigidity. Therefore, investigating Martian convective vortices with the right instrumentation can lead to a better understanding of the Martian atmospheric structures as well as the subsurface physical properties. In this study, we quantitatively characterized the convective vortices detected by NASA’s InSight mission (~13,000 events) using both meteorological (e.g., pressure, wind speed, temperature) and seismic data. The evaluated parameters, such as the signal-to-noise ratio, event duration, asymmetricity of pressure drop profiles, and cross-correlation coefficient between seismic and pressure signals, are compiled as a catalog. To demonstrate how our catalog can contribute to scientific investigations, we show two analysis results about (i) asymmetrical features seen in the vortex-related pressure drops and (ii) atmospheric-ground interaction to retrieve the subsurface physical properties.

After one year of surface operations at Jezero, the MEDA meteorological sensors have captured the signals produced by the close approach of hundreds of vortices and dust devils over different seasons and terrains. Here we update findings on the vortex and Dust Devils published in Hueso et al. (JGR: Planets, 2023). That work analyzed MEDA data from spring to early autumn identifying vortices as pressure drops and later characterizing them from the ensemble of MEDA measurements. In this updated analysis we show that, in winter, declining surface temperatures and smaller vertical gradients result in a wane of vortex activity. This decreased activity affects more the frequency of intense vortices (Δp >1.5 Pa) without showing a stiff decay in the total number of vortices (Δp>0.5 Pa). In this contribution we concentrate on the specific aspects of the thermodynamics of the vortices from temperature measurements obtained by MEDA that characterize the vertical thermal gradient at the time of the vortex passage. In addition, when vortices approach the rover closely in a favorable geometry (coming from the front of the vortex) we measure the increased temperatures inside the vortex. We also explore the increased nighttime vortex activity found on some sols, when pressure drops equivalent to those created by daytime vortices appear in the early morning before sunrise, with clusters of nighttime activity in winter and early spring.

The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defense, intended to validate kinetic impact as a means of asteroid deflection. Here we report the first determination of the momentum transferred to an asteroid by kinetic impact. Based on the change in the binary orbit period, we find an instantaneous reduction in Dimorphos's along-track orbital velocity component of 2.70 +/- 0.10 mm/s, indicating enhanced momentum transfer due to recoil from ejecta streams produced by the impact. For a Dimorphos bulk density range of 1,500 to 3,300 kg/m$^3$, we find that the expected value of the momentum enhancement factor, $\beta$, ranges between 2.2 and 4.9, depending on the mass of Dimorphos. If Dimorphos and Didymos are assumed to have equal densities of 2,400 kg/m$^3$, $\beta$= 3.61 +0.19/-0.25 (1 $\sigma$). These $\beta$ values indicate that significantly more momentum was transferred to Dimorphos from the escaping impact ejecta than was incident with DART. Therefore, the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos., Comment: accepted by Nature

While no known asteroid poses a threat to Earth for at least the next century, the catalog of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation. Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid. A test of kinetic impact technology was identified as the highest priority space mission related to asteroid mitigation. NASA's Double Asteroid Redirection Test (DART) mission is the first full-scale test of kinetic impact technology. The mission's target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by DART's impact. While past missions have utilized impactors to investigate the properties of small bodies those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft's autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in Dimorphos's orbit demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary., Comment: Accepted by Nature

NASA's InSight lander successfully touched down on Mars in November 2018, and, for the first time, a seismometer was deployed on the surface of the planet. The seismic recordings reveal diurnal and seasonal changes of the broadband noise level that are consistent with variations of the local atmospheric conditions. The seismic data include a variety of spectral peaks, which are interpreted as wind‐excited, mechanical resonances of the lander, resonances of the subsurface, or artifacts produced in the measurement system. Understanding the origin of these signals is critical for the detection and characterization of marsquakes as well as for studies investigating the ambient noise. We identify the major spectral peaks up to 9 Hz, corresponding to the frequency range the most relevant to observed marsquakes. We track the variations in frequency, amplitude, and polarization of these peaks over the duration of the mission so far. The majority of these peaks can readily be classified as measurement artifacts or lander resonances (lander modes), of which the latter have a temperature‐dependent peak frequency and a wind‐sensitive amplitude. Of particular interest is a prominent resonance at 2.4 Hz, which is used to discriminate between seismic events and local noise and is possibly produced by a subsurface structure. In contrast to the lander modes, the 2.4 Hz resonance has distinctly different features: (1) a broad and stable spectral shape, slightly shifted on each component; (2) predominantly vertical energy; (3) temperature‐independent peak frequency; (4) comparatively weak amplification by local winds, though there is a slow change in the diurnal and seasonal amplitude; and (5) excitation during all seismic events that excite this frequency band. Based on these observations, we suggest that the 2.4 Hz resonance is the only mode below 9 Hz that could be related to a local ground structure., Bulletin of the Seismological Society of America, 111 (6), ISSN:0037-1106, ISSN:1943-3573

Statler et al., NASA’s Double Asteroid Redirection Test (DART) is the first full-scale test of an asteroid deflection technology. Results from the hypervelocity kinetic impact and Earth-based observations, coupled with LICIACube and the later Hera mission, will result in measurement of the momentum transfer efficiency accurate to ∼10% and characterization of the Didymos binary system. But DART is a single experiment; how could these results be used in a future planetary defense necessity involving a different asteroid? We examine what aspects of Dimorphos’s response to kinetic impact will be constrained by DART results; how these constraints will help refine knowledge of the physical properties of asteroidal materials and predictive power of impact simulations; what information about a potential Earth impactor could be acquired before a deflection effort; and how design of a deflection mission should be informed by this understanding. We generalize the momentum enhancement factor β, showing that a particular direction-specific β will be directly determined by the DART results, and that a related direction-specific β is a figure of merit for a kinetic impact mission. The DART β determination constrains the ejecta momentum vector, which, with hydrodynamic simulations, constrains the physical properties of Dimorphos’s near-surface. In a hypothetical planetary defense exigency, extrapolating these constraints to a newly discovered asteroid will require Earth-based observations and benefit from in situ reconnaissance. We show representative predictions for momentum transfer based on different levels of reconnaissance and discuss strategic targeting to optimize the deflection and reduce the risk of a counterproductive deflection in the wrong direction., This work was supported in part by the DART mission, NASA contract No. 80MSFC20D0004 to JHU/APL. Some of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). S.C. acknowledges funding through the Crosby Fellowship of the Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology. E.D., S.I., A.L., M.P., A.R., and P.T. are grateful to the Italian Space Agency (ASI) for financial support through agreement No. 2019-31-HH.0 in the context of ASI’s LICIACube mission, and agreement No. 2022-8-HH.0 for ESA’s Hera mission. R.L. appreciates the funding from the European Union’s Horizon 2020 research and innovation program, grant agreement No. 870377 (project NEO-MAPP). P.M. acknowledges funding support from the French space agency CNES, ESA and the European Union’s Horizon 2020 research and innovation program under grant agreement No. 870377 (project NEO-MAPP). R.M. acknowledges support from a NASA Space Technology Graduate Research Opportunities (NSTGRO) Award (80NSSC22K1173). R.N. acknowledges support from NASA/FINESST (NNH20ZDA001N). J.O. and I.H. were supported by the Spanish State Research Agency (AEI) project No. MDM-2017-0737 Unidad de Excelencia “María de Maeztu”—Centro de Astrobiología (CSIC-INTA). They are also grateful for all logistical support provided by Instituto Nacional de Técnica Aeroespacial (INTA). S.R.S. acknowledges support from the DART Participating Scientist Program, grant No. 80NSSC22K0318. J.M.T.R. was funded by FEDER/Ministerio de Ciencia e Innovación—Agencia Estatal de Investigación of Spain (grant No. PGC2018-097374-B-I00).

Past, present and future small body missions include onboard accelerometers that are used either by main spacecraft during surface interactions such as sampling or touching the surface [1-2], or by lander packages deployed to the surface [3-6]. All surface interactions provide a wealth of information about the behaviour and the properties of surface materials but accelerometer data is particularly valuable. However, particular care must be taken to correctly account for the low gravity environment when interpreting the measurements. As long as the proper (Froude number) scaling is applied, the collision duration and penetration depth derived from the acceleration data can be used to infer surface properties such as the internal friction angle or the bulk density of the material [7]. Previous work has demonstrated the link between collision velocity and peak acceleration in both terrestrial and low-gravity experimental trials [8-9]. Here we will present recent experimental results investigating the link between accelerometer data and the surface properties. The collision velocity is adjusted by modifying the drop height of the projectile and impacts are performed into several different surface materials (Fig. 1). Figure 1. The granular materials used in the experimental trials To obtain the in-situ acceleration profile during the collision, we use a projectile that contains an accelerometer. We apply the same data processing for the accelerometer measurements as used in previous work [8-9] to extract the drop height (zdrop), the collision velocity (vc), the collision duration (tstop) and the peak acceleration (apeak). In addition, we also extract the time between the instant the projectile makes contact with the ground and the moment when the projectile is at its peak acceleration (tpeak), the mean amplitude of acceleration fluctuations after the peak acceleration, and the frequency of these fluctuations (Fig. 2). As noted in previous work [10,11], the acceleration profiles have a clear dependence on particle size (Fig. 3). In this talk we will present new experimental results and discuss the information that can be extracted from accelerometers about the surface properties during . Figure 2: Typical profile measured by an in-situ accelerometer in a spherical projectile during an impact into granular material. See text for description of the variables indicated. Figure 3: Acceleration profile during the impacts with different granular materials, and different collision velocities: 0.5 m/s (blue), 0.8 m/s (red), 1.2 m/s (yellow). Acknowledgements The authors acknowledge funding support from the European Commission's Horizon 2020 research and innovation programme under grant agreement No 870377 (NEO-MAPP project). This project also received funding from the Centre National d'Etudes Spatiales (CNES) and CS acknowledges PhD research grant funding from ISAE-SUPAERO. References: [1] Lauretta, D.S. and the OSIRIS-REx Team, 2021, March. The OSIRIS-REx Touch-and-Go Sample Acquisition Event and Implications for the Nature of the Returned Sample. In Lunar and Planetary Science Conference (No. 2548, p. 2097). [2] DellaGiustina D., et al. 2022, OSIRIS-APEX: A PROPOSED OSIRIS-REX EXTENDED MISSION TO APOPHIS, Apophis T-7 Years 2022 (LPI Contrib. No. 2681) [3] Lorenz, R.D., et al. 2009. Titan surface mechanical properties from the SSP ACC–I record of the impact deceleration of the Huygens probe. [4] Biele, J., Ulamec, S., Maibaum, M., Roll, R., Witte, L., Jurado, E., Muñoz, P., Arnold, W., Auster, H.U., Casas, C., Faber, C., and others, 2015. The landing (s) of Philae and inferences about comet surface mechanical properties. Science, 349(6247), p.aaa9816. [5] Michel et al., 2022, The ESA Hera mission: Detailed characterisation of the DART impact outcome and of the binary asteroid (65803) Didymos, The Planetary Science Journal (accepted) [6] Michel, P., et al. 2022, The MMX rover: performing in situ surface investigations on Phobos. Earth Planets Space 74, 2 [7] Sunday, C., et al. 2022. The influence of gravity on granular impacts-II. A gravity-scaled collision model for slow interactions. Astronomy & Astrophysics, 658, p.A118. [8] Murdoch, N., et al. 2017. An experimental study of low-velocity impacts into granular material in reduced gravity. Monthly Notices of the Royal Astronomical Society, 468(2), pp.1259-1272. [9] Murdoch, N., et al. 2021. Low-velocity impacts into granular material: application to small-body landing. Monthly Notices of the Royal Astronomical Society, 503(3), pp.3460-3471. [10] Clark et al., 2013, Granular impact dynamics: Fluctuations at short time-scales, AIP Conference Proceedings 1542, 445-448 [11] Duchêne, A., et al. 2022, A Machine Learning Approach For Estimating Asteroid Surface Properties from Accelerometer Measurements, Lunar and Planetary Science Conference 2022, no. 1563

We study rover-regolith interactions in low-gravity environments by conducting soft-sphere discrete element method (SSDEM) simulations with a simplified rover wheel and a bed of spherical particles. The simulations reveal that rover performance scales according to the Froude number, or a dimensionless parameter which accounts for the size of the wheel, the rotational velocity of the wheel, and gravity. This relationship provides valuable insight into how to operate rovers and analyze wheel-regolith interactions during future rover missions.IntroductionWheeled-rovers are useful tools for identifying the surface material properties of planetary surfaces [1-3]. The sinkage and traction of a rover can be used to assess the bearing strength of a material, and the tracks left behind by a rover’s wheels can provide information regarding the density, the friction angle, and the cohesion of the regolith [3]. To maximize the scientific return from a rover mission, however, the vehicle must first be able to drive on a granular terrain in a reduced-gravity environment. Parabolic flight experiments and numerical simulations have shown that, as gravity decreases, wheel slip increases and rover traction decreases [4-6]. At the same time, wheel sinkage remains comparable for different gravity levels, at least for certain types of materials [4]. While a few models have been proposed to help explain these findings [7,8], an explicit scaling relationship between rover performance and gravity has yet to be established.In this work, we analyze rover-regolith interactions on Earth versus a small moon, Phobos. Based on the findings of [8] and [9], we hypothesize that rolling behavior scales with gravity according to the dimensionless Froude number, Fr = Lω^2/g, where L is a characteristic length (e.g., the radius of a rover wheel), ω is the rotational velocity of the wheel, and g is gravity.SimulationsWe conducted SSDEM simulations using a simplified rover wheel and the MULTICORE module of the open-source code CHRONO [10, 11]. The rover wheel is 214 mm in diameter and 53 mm in width and has 9 thin grousers that are equally spaced around a cylindrical hub. The wheel rotates at a constant speed through a bed of spherical grains and can translate freely in the horizontal and vertical directions. The grains are 6 +/- 0.5 mm in diameter and are contained within a 800x250x150 mm box. Simulations were performed using different material cases (e.g., glass beads, rough glass beads, and rough glass beads with cohesion), two gravity levels (g = 9.81 and 0.006 m/s2), and several wheel speeds (ω = 0.065-2.65 rad/s). Fig. 1 provides a snapshot of a typical simulation. We evaluate driving performance by comparing the travel distance of the wheel Δx as a function of its angular displacement Δθ. We also compare the static and dynamic sinkage of the wheel for the different simulation cases. Fig. 1: Snapshots from a simulation where gravity is 9.81 m/s2 and the rotational velocity is 0.65 rad/s. The container is filled with 6 +/- 0.5 mm spherical particles which are colored by their vertical positions at the start of the simulation [12].ResultsWe find that static wheel sinkage is independent of gravity for simulations with cohesionless materials. Like previous works, we also find that driving performance decreases as gravity decreases for configurations with similar driving speeds (Fig. 2a). We also observe, however, that rover performance is comparable for configurations with similar Froude numbers (Fig. 2b). This means that driving on a cohesionless granular material on Earth at 0.2 m/s is like driving on the same material at 0.005 m/s on Phobos. Fig. 2: Travel distance Δx by angular displacement Δθ for a wheel rotating through rough glass beads on Earth and Phobos. Plot (a) shows results for similar wheel speeds and plot (b) shows results for similar Froude numbers [12].To understand these findings, we consider wheel-regolith interactions in terms of granular regimes. When a wheel initially sinks into a granular material, the system is in a quasi-static state. Sinkage is independent of gravity, because the reduced strength of the material is offset by the reduced weight of the wheel [4,7]. Then, as the wheel turns, the grains become fluidized, and above a certain velocity, the system enters the inertial regime. For similar wheel velocities, the system might be in a quasi-static state on Earth but in an inertial regime on Phobos. This explains why traction decreases as gravity decreases. For similar Froude numbers, however, the system will be in the same regime regardless of gravity level. Fig. 3 illustrates this point further by comparing the velocity fields of the particles in the different simulations. Overall, we demonstrate how the Froude relationship can be a powerful tool for planning rover operations and for interpreting surface interactions during future rover missions. Fig.3: Velocity field of the particles beneath a rover wheel for simulations in rough glass beads on Earth and Phobos. Plots (a) and (b) show results for similar wheel speeds and plots (c) and (d) show results for similar Froude numbers.AcknowledgementsThis work was funded by ISAE-SUPAERO and CNES through a PhD research grant. The simulations were conducted using HPC resources from CALMIP under grant 2019-P19030. NM acknowledges funding support from CNES.References[1] Sullivan, R., et al. Journal of Geophysical Research: Planets, 116(E2), 2011. [2] Gao, Y., et al. Advances in Space Research, 58(9):1893–1899, 2016. [3] Ding, L., et al. Preprint, 2021. [4] Kobayashi, T., et al. Journal of Terramechanics, 47(4):261–274, 2010. [5] Kovács, L., et al. Journal of Field Robotics, 37(5):754–767, 2020. [6] Nakashima, H. and Kobayashi, T. Journal of Terramechanics, 53:37–45, 2014. [7] Wong, J. Y. and Kobayashi, T. Journal of Terramechanics, 49(6):349–362, 2012. [8] Slonaker, J., et al. Physical Review E, 95(5):052901, 2017. [9] Sunday, Cecily, et al. Astronomy & Astrophysics, 658 A118, 2022. [10] Tasora, A., et al. High Performance Computing in Science and Engineering. Springer International Publishing, 2016. [11] Sunday, C., et al. Monthly Notices of the Royal Astronomical Society, 498(1):1062–1079, 2020. [12] Sunday, C. PhD Thesis, ISAE-SUPAERO, 2022.

The aim of this investigation is to carry out a study of the variability of nocturnal atmospheric turbulence at Jezero crater supported by modeling effort and monitored by MEDA. The rapid turbulent kinetic energy (hereafter TKE), wind and pressure fluctuations observed during nighttime both with modeling and MEDA is a clear indicator of nocturnal turbulence. The origin of this nocturnal turbulence is explored with MRAMS and, as opposed to Gale crater, low evidence of significant gravity waves activity during the whole period studied was found. On the contrary, the nighttime turbulence at Jezero crater could be shear driven and may be explained due to an enhanced mechanical turbulence produced by increasingly strong shear (onset of a strong low-level jet) at the nocturnal inversion interface. As the nocturnal inversion develops, the winds above become decoupled from the surface and the decrease in friction produces a net acceleration [refs 4, 5, 6, 7]. Once the critical Richardson Number is reached (Ri ∼< 0.25, Figure 3), shear instabilities can mix warmer air aloft down to the surface [refs 8, 9, 10]. 1. Introduction The Mars 2020 Perseverance rover landed in Mars in February 2021 at 18.44°N 77.45°E within and near the northwest rim of Jezero crater. The MEDA weather station is aboard Perseverance rover [ref 1]. 2. MRAMS mesoscale simulations MRAMS was applied to Mars 2020 landing site region using nested grids with a spacing of 330 meters on the innermost grid that is centered over the landing site [ref 2]. 3. Nighttime turbulence modeled with MRAMS The effect of subgrid-scale eddies is captured within MRAMS via a prognostic TKE (Figure 1) equation [ref 3]. MRAMS shows a peak in TKE during the afternoon, which is consistent with the modeled high-frequency variations in air temperatures [Figure 3 of ref 2]. The sudden increase in air temperature during the evenings [Figure 3 of ref 2] at the onset of radiative cooling is produced by mechanically driven turbulence since the atmosphere is stable and non-convective in the evening. The model does often show small increases of TKE during the night (Figure 1), especially during Ls=180º (corresponding to Mars 2020 sol 362) and some during Ls 105 and Ls 160 (corresponding to Mars 2020 sols 216 and 326), that could be associated with the turbulent aspects of the nighttime dynamical flows when compared with nearby locations with more flat topography. During the late evening and night, MRAMS is resolving thermal variations [2, Figure 3] and does often show small increases of TKE at that time (Figure 1). The rapid air temperature fluctuations modeled at night in all seasons is indicative of nocturnal turbulence. There is low evidence of significant wave activity during the whole period studied and only some gravity waves were found. The nighttime turbulence could be attributed to shear driven turbulence and may be explained due to an enhanced mechanical turbulence driven by increasingly strong shear, with the onset of the nocturnal low-level jet, at the nocturnal inversion interface (an example on Figure 2). Based on GCM model efforts, looks like the low-level jet is a large scale circulation feature. The westward wind at 2 km altitude shown on Figure 2 is also show up nicely in the MCD. The jet could be forced by the diurnal cycle. The dustier atmosphere, when arrival of northern autumn equinox, also contributes to decrease the nighttime Richardson number by two means: strengthening of the nighttime low-level jet deeping the near-surface wind shear and weakening near-surface atmospheric stability by increasing the nighttime surface temperature and decreasing of atmospheric temperature. A third possible strengthening of the nighttime turbulence at Jezero could be the convergence, after 01:00 LTST, of downslope winds blowing from NW rim fighting against SE winds blowing both from east crater rims and from Jezero mons (located SE outside the crater), producing a big whirlpool inside the crater (Figure 4) that could be the responsible of the high variability of wind directions observed by MEDA. 4. Nightime turbulence observed with MEDA The rapid fluctuations of pressure (moreover during high dust periods), TKE (derived only with horizontal wind speeds, that will be updated with vertical winds in the future) and wind speeds observed during nighttime with MEDA (Figures 5 and 6) is a clear indication of nocturnal turbulence. 5. Figures Figure 1: TKE diurnal cycle predicted with MRAMS for Jezero crater at Ls0, 60, 90, 105, 160, 180 and 270. Figure 2: MRAMS vertical cross-section (Jezero’s west rim to east rim) at 21:35 LTST of Ls=180º -corresponding to Mars 2020 sol #362- of total wind (zonal + meridional) in colored shadowed, zonal + vertical (exaggerated x5) wind in white arrows and TKE in black contours. The west crater rim is the hill on the left. Perseverance rover is located at x ≈ 17 km. Figure 3: MRAMS vertical profiles of wind magnitude, wind shear, Richardson number (Ri) and TKE for Ls180 at Mars 2020 location corresponding to Mars 2020 sol #362 (Ls=180º). Once the critical Richardson Number is reached (Ri ∼< 0.25, red line). Figure 4: Near-surface winds (vectors) and potential temperature (shaded) as predicted on numerical grid 5. Vectors are plotted at every other grid point. Topography contours are shown in black. Wind vector scale is shown in the bottom right area of the panels. hh:mm LTST on the top right. A big whirlpool inside the crater could be responsible for the large variability of wind directions observed by MEDA after 01:00 LTST. Figure 5: MEDA TKE (derived only with horizontal wind speeds, that will be updated with vertical winds in the future), wind direction and horizontal wind speed instantaneous measurements for the period 00:14 to 00:23 LTST at sol #73. Figure 6: Diurnal cycle of MEDA TKE averaged over 5 min for sols #73-87. 6. References [1] Rodriguez-Manfredi et al. 2020; [2] Pla-Garcia et al. 2021; [3] Mellor and Yamada 1974; [4] Davis 2000; [5] Blackadar 1957; [6] Thorpe and Guymer 1977; [7] Mahrt 1981; [8] Miles 1961; [9] Banfield et al. 2020; [10] Chatain et al. 2021

In this abstract we discuss a proposal for a microgravity flight campaign within which we will investigate penetrometry in a microgravity environment. Understanding the mechanical properties of solar system minor bodies is essential for understanding their origin and evolution. Past missions such as Hayabusa-2 and OSIRIS-REX have landed on asteroids and taken samples to discover what these bodies are made of. However, there has been conflicting evidence and reports into the physical properties of the granular surface material of these bodies. With future missions such as JAXA’s MMX mission travelling to Phobos to take a sample of the body the results from this campaign will be very important to that and future missions. Penetrometry, i.e. the determination of the reaction force an object experiences as it penetrates into a surface, can help to understand the essential properties regarding regolith such as grain size, grain shape, cohesion and bulk density. The usage of penetrometry however has mostly been limited ground-based studies such as soil sciences or even cheese maturation. Very little is known about the underlying physics of penetrometry. Results of penetrometry experiments are largely analysed based on empirical models, which presents us with a challenge if we want to apply the same parameters to understand granular materials on asteroid surfaces. Obviously, gravity cannot be eliminated in the laboratory. Hence, it is essential to verify penetrometry as a method and validate penetrometry instrument designs in microgravity.For this purpose, we propose a parabolic flight campaign. Our experiment will test the use of penetrometry in asteroid-analogue environments by investigating samples with varying properties such as grain size and shape. The microgravity aspect of the experiment is one of the most important factors because it enables us to correlate laboratory experiments at 1g with identical setups in a gravity regime relevant to asteroids. The proposed experimental setup will include a variety of samples with varying grain sizes, grain shapes, porosities and grain size distributions. The penetrometer used will also have varying properties such as the diameter, shape, and velocity of penetration. A robotic arm will push a penetrometer into the samples to measure the reaction force which can then be used to determine the mechanical properties of the samples. By varying the samples and penetrometer properties it will be possible to better understand the relevant parameters affecting reaction force. The suitability of the setup will also be reviewed to understand its usage and applicability in microgravity environments such as the robotic arm that will be used. All of the experiments carried out during the parabolic campaign will also be done at 1g to compare the tests in varying gravity levels. With a better understanding of the science behind penetrometry and the effects of microgravity, future missions will be better prepared and be able to use penetrometry more effectively to understand small-body surfaces.

Funding Information: To achieve these objectives, Milani is carrying two scientific payloads, the ASPECT visual and near-infrared (Vis-NIR) imaging spectrometer and the VISTA thermogravimeter aimed at collecting and characterizing volatiles and dust particles below 10 μm. Additionally, navigation payloads include a visible navigation camera and lidar. The Milani consortium is composed of entities and institutions from Italy, the Czech Republic, and Finland. The consortium Prime is Tyvak International, responsible for the whole program management and platform design, development, integration, testing, and final delivery to the customer. Politecnico di Torino is tasked with defining requirements and performing thermal, radiation, and debris analysis. Politecnico di Milano is responsible for mission analysis and GNC. Altec will support the Ground Segment architecture and interface definition. Centro Italiano per la Ricerca Aerospaziale (CIRA) is responsible for the execution of the vehicle environmental campaign. HULD contributes to developing the mission-specific software. VTT is the main payload (ASPECT hyperspectral imager) provider and is supported by the following entities dealing with ASPECT-related development: University of Helsinki (ASPECT calibration); Reaktor Space Lab (ASPECT Data Processing Unit development), Institute of Geology of the Czech Academy of Sciences (ASPECT scientific algorithms requirements and testing); and Brno University of Technology (ASPECT scientific algorithms development). INAF-IAPS is the secondary Payload (VISTA, dust detector) provider. Funding Information: The Mission PI is appointed by ESA and is the primary interface to ESA. The Hera SMB consists of the ESA Hera Project Scientist (ESA PS), the Mission PI, and the Hera Advisory Board, consisting of four mission advisors. The Mission PI chairs the HIT and is supported by the Hera Advisory Board. The tasks of the Hera SMB are 1. advising the Hera mission project team on all aspects related to the Hera mission objectives; 2. ensuring that the WGs’ activities cover the needs of the Hera mission; 3. providing recommendations to ESA concerning the membership in the HIT; and 4. implementing the Publication Policy. Funding Information: Hera is the ESA contribution to the AIDA collaboration. Hera, Juventas, Milani, and their instruments are developed under ESA contract supported by national agencies. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 870377 (project NEO-MAPP), the CNRS through the MITI interdisciplinary programs, ASI, CNES, JAXA, the Academy of Finland project no. 335595, and was conducted with institutional support RVO 67985831 of the Institute of Geology of the Czech Academy of Sciences. M.L., E.P., P.T .and E.D. are grateful to the Italian Space Agency (ASI) for financial support through Agreement No. 2022-8-HH.0 in the context of ESA’s Hera mission. We are grateful to the whole Hera team, including Working Group core members and other contributors for their continuous efforts and support. Their names can be found on the following website: https:// www.heramission.space/team. Publisher Copyright: © 2022. The Author(s). Published by the American Astronomical Society. Hera is a planetary defense mission under development in the Space Safety and Security Program of the European Space Agency for launch in 2024 October. It will rendezvous in late 2026 December with the binary asteroid (65803) Didymos and in particular its moon, Dimorphos, which will be impacted by NASA’s DART spacecraft on 2022 September 26 as the first asteroid deflection test. The main goals of Hera are the detailed characterization of the physical properties of Didymos and Dimorphos and of the crater made by the DART mission, as well as measurement of the momentum transfer efficiency resulting from DART’s impact. The data from the Hera spacecraft and its two CubeSats will also provide significant insights into asteroid science and the evolutionary history of our solar system. Hera will perform the first rendezvous with a binary asteroid and provide new measurements, such as radar sounding of an asteroid interior, which will allow models in planetary science to be tested. Hera will thus provide a crucial element in the global effort to avert future asteroid impacts at the same time as providing world-leading science.

Perseverance's Mars Environmental Dynamics Analyzer (MEDA) is collecting data at Jezero Crater, characterizing the physical processes in the lowest layer of the atmosphere as no previous instrument did before. Here we show that temperature measurements at four heights capture the response of the atmospheric surface layer to multiple phenomena. We observe the transition from a stable nighttime thermal inversion to a diurnal, highly turbulent convective regime, with large vertical thermal gradients, and where local surface properties (such as Thermal Inertia) play an essential role. Recording multiple daily optical depths yielded higher aerosol concentrations in the morning than in the afternoon. Measured wind patterns are mainly driven by local topography, with a small contribution from regional winds. Daily and seasonal variability of relative humidity shows a complex hydrologic cycle. These observations raise new puzzles in which changes in surface albedo and thermal inertia may play an influential role. On a larger scale, surface pressure shows typical signatures of gravity waves and baroclinic eddies in a part of the seasonal cycle characterized before as low wave activity. These observations, combined and simultaneous, show the rich Jezero’s meteorology, and unveil the diversity of processes driving change on today’s Martian surface.

The Mars Moon eXploration (MMX) mission by the Japan Aerospace Exploration Agency, JAXA, which is going to explore the Martian Moons Phobos and Deimos and also return samples from Phobos back to Earth will also deliver a small (about 25 kg) Rover to the surface of Phobos.The payload of this rover consists of a Raman spectrometer (RAX) to measure the mineralogical composition of the surface material, a stereo pair of cameras looking affront (NavCam, also used for navigation) to provide the properties of the investigated area, a radiometer (miniRAD) to measure the surface brightness temperature and determine thermal properties of both regolith and rocks, and two cameras looking at the wheel-surface interface (WheelCam) to investigate the properties and dynamics of the regolith. The cameras will, thus, serve for both, technological and scientific needs.After the Rover has been delivered by the main spacecraft, it shall upright itself and operate for about 100 days on the surface of Phobos to investigate terrain and mineralogy along its path.The measurements are going to provide ground truth by studying in-situ properties such as the physical properties and heterogeneity of the surface material.MMX is planned to be launched in September 2024, the Rover delivery is currently planned for 2027.The Rover is a contribution by the Centre National d’Etudes Spatiales (CNES) and the German Aerospace Center (DLR) with additional contributions from INTA (Spain) and JAXA.

One of the particular interest of the SuperCam microphone onboard the NASA’s Perseverance rover is that it is coupled with its own reproducible sound source, the blast waves generated by the SuperCam laser-induced plasma expansion. This unique emission-reception pair on Mars is used to investigate the propagation of spark-induced N-waves through the turbulent CO2-dominated Mars atmosphere. The analysis of waveforms shows large distortions over a burst of 30 subsequent shots, which is consistent with previous laboratory recordings of N-waves through thermal turbulence. Especially, this distortion leads to a scattering of the peak pressure amplitude, whose distribution can be fitted with a generalized gamma function. For bursts recorded farther than 4 m, the distribution gets asymmetric with a shift of the maximum toward the left of the median due to peaks amplified more than twice the median amplitude, likely due to caustics that randomly focus the acoustic wave. On the other hand, over a Martian year, the absolute peak pressure varies by ∼50% due to changes in the acoustic impedance and Rankine-Hugoniot conditions, due to the seasonal cycles of pressure and temperature at the surface of Mars.

To study Mars chemistry, SuperCam onboard the NASA Perseverance rover fires bursts of 30 laser shots at rocks. Its microphone records the shock wave generated between 2 and 15 kHz by each laser-induced plasma for distances between 2 m and 8 m, at varying local times, from strong thermal turbulence during daytime, to weaker one at dusk or dawn. In each case, the scintillation index (the normalized variance of the intensity), and travel time are calculated. Based on extensive literature on the propagation of a spherical wave through a turbulent medium, there are enough statistics to constrain the field that causes the dispersion of acoustic data. Initial results show that data are well modeled by a Gaussian field. A negative time shift, ∼0.5% at 6 m, is observed: the resulting velocity is higher than the mean speed of sound (fast path effect). The variance of arrival times leads to a 15 cm characteristic scale during daytime. Fluctuations of the scintillation index allow the strength of the turbulence field to constrained. Other turbulence models are tested, including the Kolmogorov energy-cascade which typically prevails on Earth for the inertial regime, but has been challenged several times on Mars.

It is important to understand how the atmospheric conditions affect the propagation of sound waves on Mars, both for the study of the acoustic sources and of the atmosphere itself. As 3 microphones are already on Mars (2 on NASA/Perseverance and 1 on CNSA/Zhurong) and potentially more to come, a model of the propagation of sound in the Martian surface layer was needed. A first-principle acoustic attenuation model is used to quantify the excess attenuation of the Martian atmosphere. Thanks to inputs extracted from a global circulation model of Mars (the LMD Martian Climate Database), we are able to compare the magnitude of attenuation at different places and times, from 10 Hz to 20 kHz. Propagation effects are also considered by adapting a parabolic equation code to the Martian conditions. This accounts for strong temperature gradients near the surface, as well as gradients of wind speed. The acoustic reflection on the ground assumes a semi-porous medium. The turbulent fluctuations of temperature and wind speed are implemented using the frozen medium approach. The model shows that characteristics of sound waves propagation depend drastically on the local time. It provides a useful framework to interpret acoustic signal recorded on Mars. The model shows that characteristics of sound waves propagation depend drastically on the local time. It provides a useful framework to interpret acoustic signal recorded on Mars.

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.

International audience; The NASA InSight lander has recorded many pressure drops attributed to convective vortices during its first full year of data collection. However, although dust-carrying vortices (dust devils) are a common phenomenon on Mars, they have not been observed in InSight images. On Earth, magnetic signals associated with some dust devils have been reported. Data from the InSight Fluxgate Magnetometer (IFG) provide the first opportunity for similar investigations on Mars. Here, we evaluate whether magnetic signals are associated with daytime vortices. We incorporate observations of environmental conditions, measurements of ground tilt from seismic data, and data from the lander's solar panels, and consider the potential for dust-laden vortices to generate observable magnetic field signals. We find that 7.7% of pressure drop events greater than 1 Pa show a resolvable magnetic field signal at the time of the pressure drops. The resolvable magnetic signals, typically seen on the horizontal field components, are less than 1 nT in amplitude, and have no clear correlation with local time, duration, or pressure drop magnitude. During nine pressure drop events we found smoothly varying magnetic signals of at least 0.3 nT on any one component. To investigate the origin of these magnetic signals we evaluated three possible sources: solar array currents (SAC), ground and lander tilt, and triboelectric effects of lofted dust. We find that SAC and tilt could contribute a change in the magnetic field but cannot solely explain the observed signals. The observed changes in field strength could theoretically be produced via triboelectric effects, but only in the case of exceptionally large dust devils that pass close to the lander. The lack of imaged dust devils and the small number of observed magnetic signatures despite numerous measured pressure drops is consistent with at most a small proportion of dust laden convective vortices at InSight and associated predicted triboelectric effects.

This article has a correction. Please see: Erratum for the Research Article: “The dynamic atmospheric and aeolian environment of Jezero crater, Mars” - 10 February 2023 Despite the importance of sand and dust to Mars geomorphology, weather, and exploration, the processes that move sand and that raise dust to maintain Mars’ ubiquitous dust haze and to produce dust storms have not been well quantified in situ, with missions lacking either the necessary sensors or a sufficiently active aeolian environment. Perseverance rover’s novel environmental sensors and Jezero crater’s dusty environment remedy this. In Perseverance’s first 216 sols, four convective vortices raised dust locally, while, on average, four passed the rover daily, over 25% of which were significantly dusty (“dust devils”). More rarely, dust lifting by nonvortex wind gusts was produced by daytime convection cells advected over the crater by strong regional daytime upslope winds, which also control aeolian surface features. One such event covered 10 times more area than the largest dust devil, suggesting that dust devils and wind gusts could raise equal amounts of dust under nonstorm conditions. We gratefully acknowledge the huge effort by the entire Mars 2020 team to meet our launch date despite the COVID-19 pandemic, to land and deploy instruments successfully in Jezero crater, and to conduct operations on the surface of Mars since February 2021. This paper arose from discussions within the Mars 2020 Atmospheres Working Group but would not have been possible without the tremendous contributions of everyone involved in Mars 2020 operations. We wish to especially pay tribute to the many team members based in Europe who regularly work through the night as MEDA or SuperCam Payload Uplink and Downlink Leads (PULs/PDLs) or in other roles and to all those who had shifts as Atmospheres Working Group representatives during this period. Last, we gratefully acknowledge the very helpful and constructive comments from both anonymous reviewers. Funding: R.H., A.S.-L., A.M., and T.d.R.-G. are supported by Spanish Ministry of Science and Innovation project PID2019-109467GB-I00 funded by MCIN/AEI/10.13039/501100011033/ and Grupos Gobierno Vasco IT1366-19. I.A., D.T., and V.A. are supported by the Spanish National Research, Development, and Innovation Program through the grants RTI2018-099825-B-C31, ESP2016-80320-C2-1-R, and ESP2014-54256-C4-3-R. L.M., S.N., and J.G.-E. are supported by the Spanish Ministry of Economy and Competitiveness, projects ESP2014-54256-C4-1-R and AYA2015-65041-P; the Spanish Ministry of Science, Innovation, and Universities, projects ESP2016-79612-C3-1-R, ESP2016-80320-C2-1-R, RTI2018-098728-B-C31, and RTI2018-099825-B-C31; and the Spanish Ministry of Science and Innovation’s Centre for the Development of Industrial Technology, projects RTI2018-098728-B-C31 and RTI2018-099825-B-C31. Á.V.-R. and M.-P.Z. are supported by Spanish State Research Agency (AEI) project no. MDM-2017-0737 Unidad de Excelencia “María de Maeztu”–Centro de Astrobiología (INTA-CSIC). M.-P.Z. is supported by the Spanish Ministry of Science and Innovation, PID2019-104205GB-C21. M.M.B. and M.-P.Z. are supported by NASA’s Mars 2020 Participating Scientist Program. All other authors were supported by funding from the Mars 2020 mission, part of the NASA Mars Exploration Program. Work by C.E.N. was additionally funded by the InSight Participating Scientist Program.A portion of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA and funding by SMD, GCD, and STMD. Peerreview

In this study, we perform a detailed spectral analysis of the turbulent energy cascade using the in-situ observations by NASA's InSight lander on Mars. A recent study on the daytime Martian boundary layer using the InSight observations showed that the conventional Kolmogorov energy cascade of inertial sub-range fails to predict the spectral density of pressure. Here we extend this by investigating diurnal and seasonal variations in the spectral density of pressure, as the indicator of the Martian atmospheric turbulence. We show distinct spectral behaviours for the daytime and nighttime conditions. Moreover, we report the important effects of regional dust storms, gravity waves, bore and solitary waves on the turbulent energy cascade. Our results show that the presence of a dust storm and gravity wave activity can enhance the turbulence of the nighttime boundary layer of Mars despite the extreme stably stratified conditions compared to the terrestrial case.

The authors have requested that this preprint be removed from Research Square.

The InSight mission, featuring continuous high-frequency high-sensitivity pressure measurements, is in ideal position to study the active atmospheric turbulence of Mars. Data acquired during 1.25 Martian year allows us to study the seasonal evolution of turbulence and its diurnal cycle. We investigate vortices (abrupt pressure drops), local turbulence (frequency range 0.01-2 Hz) and non-local turbulence often caused by convection cells and plumes (frequency range 0.002-0.01 Hz). Contrary to non-local turbulence, local turbulence is strongly sensitive at all local times and seasons to the ambient wind. We report many remarkable events with the arrival of northern autumn at the InSight landing site: a spectacular burst of daytime vortices, the appearance of nighttime vortices, and the development of nighttime local turbulence as intense as its daytime counterpart. Nighttime turbulence at this dusty season appears as a result of the combination of a stronger low-level jet, producing shear-driven turbulence, and a weaker stability., 15 pages, 5 figures, accepted version of the manuscript published in GRL

The National Aeronautics and Space Administration InSight mission has deployed the seismic experiment, SEIS, on the surface of Mars, and has recorded a variety of signals including marsquakes and dust devils. This work presents results on the tilt and local noise sources, which provide context to aid interpretation of the observed signals and allow an examination of the near-surface properties. Our analysis uses data recorded by the short-period sensors on the deck, throughout deployment and in the final configuration. We use thermal decorrelation to provide an estimate of the sol-to-sol tilt. This tilt is examined across deployment and over a Martian year. After each modification to the site, the tilt is seen to stabilize over 3–20 sols depending on the action, and the total change in tilt is

On 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. Introduction The 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 microphone Pressure 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 sensor Pre-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 microphone Combined 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]. Conclusions The 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 2021

International audience; We report the aeolian changes observed in situ by NASA's InSight lander during the first 400 sols of operations: Granule creep, saltation, dust removal, and the formation of dark surface tracks. Aeolian changes are infrequent and sporadic. However, on sols, when they do occur, they consistently appear between noon to 3 p.m., and are associated with the passage of convective vortices during periods of high vortex activity. Aeolian changes are more frequent at elevated locations, such as the top surfaces of rocks and lander footpads. InSight observed these changes using, for the first time, simultaneous insitu and orbital imaging and high-frequency meteorological, seismological, and magnetic measurements. Seismometer measurements of ground acceleration constrain the timing and trajectory of convective vortex encounters, linking surface changes to source vortices. Magnetometer measurements show perturbations in magnetic field strength during the passage of convective vortices consistent with chargedparticle motion. Detachment of sand-scale particles occurs when high background winds and vortexinduced turbulence provide a peak surface friction wind speed above the classic saltation fluid threshold. However, detachment of dust-and granule-scale particles also occurred when the surface friction wind speed remained below this threshold. This may be explained by local enhancement of the surface roughness and other effects described here and further studied in Part 2 (Baker et al., 2021). The lack of saltation and bright dust-coated surfaces at the InSight landing site implies surface stability and the onset of particle motion may be suppressed by dust "cushioning." This differentiates the InSight landing site from other areas on Mars that exhibit more aeolian activity. Plain Language Summary Aeolian activity, the movement of dust and sand by the wind, is common on Earth and has been observed on other planets, including Mars. A new Mars lander, InSight, has for the first time monitored aeolian changes by combining imaging with weather, seismic and CHARALAMBOUS ET AL.

With the flourishing number of small body missions that involve surface interactions, understanding the mechanics of spacecraft – surface interactions is crucial for improving our knowledge about the landing phases of space missions, for preparing spacecraft operations, and for interpreting the results of measurements made during the surface interactions. Given their regolith-covered surfaces, the process of landing on a small body can be considered as an impact at low-velocity on to a granular material in reduced-gravity. In order to study the influence of the surface material, projectile shape, and gravity on the collision dynamics, we used two experimental configurations (one for terrestrial gravity experiments and one for reduced-gravity experiments) to perform low-velocity collisions into different types of granular materials: quartz sand, and two different sizes of glass beads (1.5 and 5 mm diameter). Both a spherical and a cubic projectile (with varying impact orientation) were used. The experimental data support a drag model for the impact dynamics composed of both a hydrodynamic drag force and quasi-static resistance force. The hydrodynamic and quasi-static contributions are related to the material frictional properties, the projectile geometry, and the gravity. The transition from a quasi-static to a hydrodynamical regime is shown to occur at lower impact velocities in reduced-gravity trials than in terrestrial gravity trials, indicating that regolith has a more fluid-like behaviour in low-gravity. The reduced quasi-static regime of a granular material under low-gravity conditions leads to a reduction in the strength, resulting in a decreased resistance to penetration and larger penetration depths.

On the NASA 2020 rover mission to Jezero crater, the remote determination of the texture, mineralogy and chemistry of rocks is essential to quickly and thoroughly characterize an area and to optimize the selection of samples for return to Earth. As part of the Perseverance payload, SuperCam is a suite of five techniques that provide critical and complementary observations via Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), visible and near-infrared spectroscopy (VISIR), high-resolution color imaging (RMI), and acoustic recording (MIC). SuperCam operates at remote distances, primarily 2-7 m, while providing data at sub-mm to mm scales. We report on SuperCam's science objectives in the context of the Mars 2020 mission goals and ways the different techniques can address these questions. The instrument is made up of three separate subsystems: the Mast Unit is designed and built in France; the Body Unit is provided by the United States; the calibration target holder is contributed by Spain, and the targets themselves by the entire science team. This publication focuses on the design, development, and tests of the Mast Unit; companion papers describe the other units. The goal of this work is to provide an understanding of the technical choices made, the constraints that were imposed, and ultimately the validated performance of the flight model as it leaves Earth, and it will serve as the foundation for Mars operations and future processing of the data. In France was provided by the Centre National d'Etudes Spatiales (CNES). Human resources were provided in part by the Centre National de la Recherche Scientifique (CNRS) and universities. Funding was provided in the US by NASA's Mars Exploration Program. Some funding of data analyses at Los Alamos National Laboratory (LANL) was provided by laboratory-directed research and development funds.

International audience; In preparation for the SuperCam/Mars Microphone scientific investigation, the acoustic signal associated with the plasma formation during Laser-Induced Breakdown Spectroscopy (LIBS) experiment is studied with regard to the shot-to-shot evolution of the laser induced crater morphology and plasma emission lines. A set of geological targets are depth profiled using a specifically designed LIBS setup coupled with acoustic test bench under ambient terrestrial atmosphere. Experiments confirm that the decrease of the acoustic energy as a function of the number of shots is well correlated with the target hardness/density and also demonstrate that the acoustic energy can be used as a remote tracer of the ablated volume of the target. Listening to LIBS sparks provides a new information relative to the ablation process that is independent from the LIBS spectrum.

On February 18, 2021, NASA’s Perseverance rover landed in Jezero Crater carrying the two first microphones operating on the surface of Mars: the SuperCam microphone, positioned on top of the rotating rover’s mast and the EDL microphone fixed on the body of the rover. Working flawlessly since then, they provide the first characterization of Mars’ acoustic environment in the audible range and beyond, from 20 Hz to 50 kHz. Recorded sounds originate from three main sources: the atmosphere (turbulence, wind), the shock-waves generated by the Supercam pulsed laser ablating rocks, and hardware-induced artificial sounds such as the signal generated by the high-speed rotating blades of the Ingenuity helicopter. After one year, the Perseverance playlist features more than 5 hours of martian sounds. In addition to providing an unprecedented short timescale characterization of the wind, temperature fluctuations, and the turbulence dissipative regime, this dataset highlights the unique sound propagation properties of the low-pressure CO2-dominated Mars atmosphere: acoustic impedance varying with the season, large intrinsic attenuation of the high frequencies, and the dispersion of the sound speed in the audible range. This presentation will review these results to date.

The NASA InSight lander is a geophysical and meteorological observatory operating on Mars for over a Martian year/two Earth years. Continuous records of seismic, pressure, wind and temperature data over this period have led to significant breakthroughs in determining the planet's structure and climate. With such a wealth of data now received, machine learning offers a nascent tool to extract further information. The seismic data is extremely correlated to the atmospheric conditions. Discerning the coupling between the atmosphere and ground motion is of significant interest and this work aims to predict the ground motion generated by wind and pressure forcing using machine learning techniques. From this prediction we can untangle the various contributions to ground motion, determine atmospheric/ground properties, analyse/discriminate marsquakes and potentially decorrelate waveforms to remove the atmospheric contribution. While a physical model for this atmospheric forcing is desirable, machine learning approaches the problem from an alternative view point where mathematical and algorithmic tools add the necessary complexity for fitting the data. In this way, we may be able to capture detailed variation and inform further modelling efforts.We will detail the initial application of machine learning for predicting the ground motion from the atmospheric data inputs of wind speed, wind direction, pressure and temperature. First though, we will describe the issues that need to be tackled to obtain a good prediction using the InSight data. To illustrate some of some of these problems, consider that glitches are known to occur in the seismic data. They offer a way to detect overfitting as they should not in general be predicted from atmospheric forcing. However, a subset of the glitches are correlated to temperature on top of the fact they are only visible during quiet enough periods, as are marsquakes. Therefore, they are not a normally distributed source of noise or uncorrelated from the input atmospheric data, breaking typical assumptions used for regression. A similar issue is presented by the changing weather conditions throughout a Martian sol, where the time series distribution varies. As a result, prior information on the instrumentation and data qualities is essential for applying the machine learning methods and interpretation of the results.We demonstrate the specifics of the InSight data with respect to 1) how a curve fitting problem can be constructed, 2) the necessary degrees of freedom of the problem, 3) consideration of non-stationary/heteroscedastic errors and 4) the optimisation and machine learning method applied. Current results will be presented from the implementation of random forests and gaussian processes. These results demonstrate a good performance so far for capturing the global variation and we will offer perspectives on how these results can be used and improved.

On the first hundreds of sols in which the InSight lander operated on the surface of Mars, its instrumentation has proven to be particularly suitable to unveil and understand atmospheric variability at all temporal scales, from the synoptic scale (baroclinic waves) to the sub-hour scale (gravity waves, bores) down to the turbulent scale (vortices, gusts, infrasounds). Recently, the InSight lander achieved a complete Martian year of observations of the atmosphere of Mars -- allowing for the seasonal variability of the Martian atmosphere and its phenomena at all scales to be monitored almost continuously, including during several large dust storms episodes. In this presentation, based on this Martian year of InSight observations, we will review the annual CO2 sublimation / condensation cycle, the variability of large-scale meteorology, the statistics of a year of wind observations -- and insightful comparisons with global climate models, the strong seasonal variability of gravity wave and turbulent activity, including a burst of activity of convective vortices in Mars' southern summer. We will also discuss how the atmosphere influences seismic and magnetic signals captured by InSight -- and the search for Martian infrasound.