The return home of the OSIRIS-REx spacecraft in September 2023 marked only the fifth time that an artificial object entered the Earth's atmosphere at interplanetary velocities. Although rare, such events serve as valuable analogs for natural meteoroid re-entries; enabling study of hypersonic dynamics, shock wave generation, and acoustic-to-seismic coupling. Here, we report on the signatures recorded by a dense (100 m scale) 11-station array located almost directly underneath the capsule's point of peak atmospheric heating in northern Nevada. Seismic data are presented, which allow inferences to be made about the shape of the shock wave's footprint on the surface, the capsule's trajectory, and its flight parameters.

The properties of the first kilometers of the Martian atmospheric Planetary Boundary Layer have until now been measured by only a few instruments and probes. InSight offers an opportunity to investigate this region through seismoacoustics. On six occasions, its seismometers recorded short low-frequency waveforms, with clear dispersion between 0.4 and 4Hz. These signals are the air-to-ground coupling of impact-generated infrasound, which propagated in an low-altitude atmospheric waveguide. Their group velocity depends on the structure of effective sound speed in the boundary layer. Here, we conduct a Bayesian inversion of effective sound speed up to 2000m altitude using the group velocity measured for events S0981c, S0986c and S1034a. The inverted effective sound speed profiles are in good agreement with estimates provided by the Mars Climate Database. Differences between inverted and modeled profiles can be attributed to a local wind variation in the impact → station direction, of amplitude smaller than 2m/s.

We quantify the total attenuation, kappa, and the attenuation component due to near-surface site effects, kappa(0), in a region in northern New Mexico using data recorded by the Los Alamos Seismic Network. The area is characterized by low seismicity, where most of the well-recorded earthquakes have magnitudes between 1 and 2. This magnitude range poses a challenge for commonly used kappa methods because the high-frequency attenuation cannot be confidently isolated from the bandwidth in which the corner frequency roll-off occurs. We determine through synthetic experiments that estimates of kappa within this range have quantifiable biases that depend on source (corner frequency), site (kappa magnitude), and data quality characteristics (fitting bandwidth), which can be used to correct estimated kappa from three commonly used kappa methods. Using 412 recorded earthquakes, we show that a bias correction results in kappa distributions and kappa(0) estimates that are more consistent between the three methods, suggesting that the bias correction results in kappa values with higher fidelity. Using the bias-corrected kappa, we find kappa(0) between 0.038 and 0.049 s within the Valles Caldera and between 0.026 and 0.066 s on Los Alamos National Laboratory property, values near those commonly used in the western United States. We find that a main limitation in the quality of kappa(0) is the small number of usable waveforms at some stations, which will to improve as more earthquakes are recorded. This contrasts with other aspects, such as fitting bandwidth and source and path variability, which are unlikely to change in the future and will ultimately be the limiting factor in kappa(0) resolution. Overall, our results suggest that the bias-correction scheme presented here could potentially be used in other regions where small-magnitude earthquakes are prevalent. However, future work should look to verify that bias-corrected kappa estimates show consistency with those retrieved from higher magnitude earthquakes.

Hypersonic re-entries of spacecraft are valuable analogues for the identification and tracking of natural meteoroids re-entering the Earth's atmosphere. We report on the detection of seismic and acoustic signals from the OSIRIS-REx landing sequence, acquired near the point of peak capsule heating and recorded using a fully off-grid Raspberry PiShake sensor. This simple setup is able to record all the salient features of both the seismic and acoustic wavefields; including the primary shockwave, later reverberations, and possible locally induced surface waves. Peak overpressures of 0.7~Pa and ground velocities of 2x10$^{-6}$~m/s yield lower bound on the air-to-ground coupling factor between 3 and 44~Hz of 1.4x10$^{-6}$m/s/Pa, comparable to results from other re-entries

SUMMARY Meteorite impacts have proved to be a significant source of seismic signal on the Moon, and have now been recorded on Mars by InSight seismometers. Understanding how impacts produce seismic signal is key to the interpretation of this unique data, and to improve their identification in continuous seismic records. Here, we use the seismic Representation Theorem, and particularly the stress glut theory, to model the seismic motion resulting from impact cratering. The source is described by equivalent forces, some resulting from the impactor momentum transfer, and others from the stress glut, which represents the mechanical effect of plasticity and non linear processes in the source region. We condense these equivalent forces into a point-source with a time-varying single force and nine-component moment tensor. This analytical representation bridges the gap between the complex dynamics of crater formation, and the linear point-source representation classically used in seismology. Using the multiphysics modelling software HOSS, we develop a method to compute the stress glut of an impact, and the associated point-source from hypervelocity impact simulations. For a vertical and an oblique impact at 1000 m s−1, we show that the moment tensor presents a significant deviatoric component. Hence, the source is not an ideal isotropic explosion contrary to previous assumptions, and draws closer to a double couple for the oblique impact. The contribution of the point force to the seismic signal appears negligible. We verify this model by comparing two signals: (1) HOSS is coupled to SPECFEM3D to propagate the near-source signal elastically to remote seismic stations; (2) the point-source model derived from the stress-glut theory is used to generate displacements at the same distance. The comparison shows that the point-source model is accurately simulating the low-frequency impact seismic waveform, and its seismic moment is in trend with Lunar and Martian impact data. High-frequencies discrepancies exist, which are partly related to finite-source effects, but might be further explained by the difference in mathematical framework between classical seismology and HOSS’ numerical modelling.

The properties of the first kilometers of the Martian atmospheric Planetary Boundary Layer have until now been measured by only a few instruments and probes. InSight offers an opportunity to investigate this region through seismoacoustics. On six occasions, its seismometers recorded short low-frequency waveforms, with clear dispersion between 0.4 and 4 Hz. These signals are the air-to-ground coupling of impact-generated infrasound, which propagated in an low-altitude atmospheric waveguide. Their group velocity depends on the structure of effective sound speed in the boundary layer. Here, we conduct a Bayesian inversion of effective sound speed up to 2,000 m altitude using the group velocity measured for events S0981c, S0986c and S1034a. The inverted effective sound speed profiles are in good agreement with estimates provided by the Mars Climate Database. Differences between inverted and modeled profiles can be attributed to a local wind variation in the impact -> station direction, of amplitude smaller than 2 m/s. The Martian Planetary Boundary Layer corresponds to the first few kilometers of the atmosphere. The InSight lander offers the opportunity to investigate its properties via the coupling of seismic and acoustic waves. Impact-generated infrasound waves were recorded for the first time on Mars by the seismometers of the InSight mission. These infrasound waves propagated in an atmospheric waveguide in the first kilometers above the Martian surface, and thus present a frequency-dependent group velocity. This frequency-dependence, also known as a dispersion relation, is influenced by the structure of the speed of sound in the waveguide. Here, we use group velocity measured for events S0981c, S0986c and S1034a to invert the variations of effective sound speed between 0 and 2,000 m altitude. For the three events, the inverted profiles are in good agreement with estimates provided by the Mars Climate Database using global climate modeling. The differences between inverted and modeled profiles can be attributed to a local variation in wind in the impact -> station direction, with magnitude smaller than 2 m/s. InSight recorded impact-generated infrasound on Mars. Their group velocity is sensitive to the structure of the atmospheric boundary layer We conduct a Bayesian inversion of effective sound speed profiles with altitude based on group velocities measured for three impact events The inverted profiles provide an indirect measurement of the Martian boundary layer, and validate models of the Mars Climate Database

Inspection of geological material is one of the main goals of the Perseverance rover during its journey across the landscape of the Jezero crater in Mars. NASA's rover integrates SuperCam, an instrument capable of performing standoff characterization of samples using a variety of techniques. Among those tools, SuperCam can perform laser-induced breakdown spectroscopy (LIBS) studies to elucidate the chemical composition of the targets of interest. Data from optical spectroscopy can be supplemented by simultaneously-produced laser-produced plasma acoustics in order to expand the information acquired from the probed rocks thanks to the SuperCam's microphone (MIC) as it can be synchronized with the LIBS laser. Herein, we report cover results from LIBS and MIC during Perseverance's first 380 sols on the Martian surface. We study the correlation between both recorded signals, considering the main intrasample and environmental sources of variation for each technique, to understand their behavior and how they can be interpreted together towards complimenting LIBS with acoustics. We find that louder and more stable acoustic signals are recorded from rock with compact surfaces, i.e., low presence loose particulate material, and harder mineral phases in their composition. Reported results constitute the first description of the evolution of the intensity in the time domain of shockwaves from laser-produced plasmas on geological targets recorded in Mars. These signals are expected contain physicochemical signatures pertaining to the inspected sampling positions. As the dependence of the acoustic signal recorded on the sample composition, provided by LIBS, is unveiled, the sound from sparks become a powerful tool for the identification of mineral phases with similar optical emission spectra.

ABSTRACT Seismoacoustic signals at local distance (<∼10 km) are widely used as important constraints on source parameters for near-surface events, yet the seismoacoustic wave generation and energy partitioning are not fully understood. Spatially dense sensors could provide observations in high resolution to capture the full wavefield for better understanding wave propagation and improving source estimation. Recently, spatially dense observations of the local seismoacoustic wavefield produced by a pair of 1-ton surface explosions have been recorded using a large-N seismic array. This large-N array consists of 446 geophones and covers an area of approximately 2×2.5 km2. The two surface explosions occur at the same location but at different times with different atmospheric conditions. Both seismic and air–ground coupled acoustic waves from the two surface explosions are well observed. Analyses of signals recorded by the large-N seismic array show different acoustic wave speed and amplitude for the two explosions. A strong spatial variability in acoustic wave speed and amplitude for each explosion is also observed. The observations suggest the important role of local atmosphere state on wave propagation and source estimation and demonstrate how the use of a large-N capability can improve characterization of the propagation medium and source.

Two >130-meter-diameter impact craters formed on Mars during the later half of 2021. These are the two largest fresh impact craters discovered by the Mars Reconnaissance Orbiter since operations started 16 years ago. The impacts created two of the largest seismic events (magnitudes greater than 4) recorded by InSight during its 3-year mission. The combination of orbital imagery and seismic ground motion enables the investigation of subsurface and atmospheric energy partitioning of the impact process on a planet with a thin atmosphere and the first direct test of martian deep-interior seismic models with known event distances. The impact at 35°N excavated blocks of water ice, which is the lowest latitude at which ice has been directly observed on Mars.

Introduction: Sound propagation properties strongly depend on the physical conditions (temperature, density, pressure) as well as the composition of the medium within which acoustic waves travel. The two microphones of the Perseverance rover [1-3] are the first ones to be deployed in the Mars atmosphere with the landing of the mission on Mars on Feb 18, 2021. The SuperCam microphone which was primarily designed to study the acoustic signal generated by the laser-induced breakdown spectroscopy technique (LIBS) [3] has recorded numerous other sounds on Mars, some created by atmospheric phenomena such as winds and turbulences due to the day/night cycle [4] or rover-induced mechanical noise. In addition, microphones can be used to probe and characterize the atmosphere [5-6]. In fact, in situ measurements are still needed to test existing sound propagation models of the Mars atmosphere. The main source of uncertainty for such models is the attenuation related to the relaxation time of CO2 at Mars pressure and temperature. Two models were developed in anticipation of the 1998 Mars Polar Lander, one using a quasi-empirical approach [7], and one using theoretical considerations [8]. A more recent model was developed using first-principles calculations [6]. These models predict different attenuation level in the frequency band generated by LIBS [9] (Chide, pers. comm.). Measurement of the amplitude of acoustic signal with controlled sources and for different frequency bands are needed to determine attenuation properties of atmospheres of different planets/moons and establish attenuation models. Another benefit of laboratory experiments are that they offer the possibility to interpret SuperCam microphone data. In the laboratory, LIBS experiments can be carried-out in very controlled atmospheric conditions allowing to explore effects of LIBS target surface properties such as hardness (Lanza et al, 2020), optical absorption, porosity... [10-11] Methods: LIBS acoustic data. In 2020, we performed a series of acoustic experiments in a large (~2m long and 1 m diameter cylinder) thermal-vacuum (TVAC) chamber at the Los Alamos National Laboratory (LANL) that is designed for testing space hardware under a variety of relevant environmental conditions (Fig. 1). A standoff LIBS experiment was set up in the TVAC chamber. Samples were placed at one end of the chamber opposite the chamber window and two microphones were placed at 28cm and 67cm from the sample plate. The two microphones are Brüel Kjær (B&K) microphones for the frequency range 20Hz to 20kHz, one 1⁄4’’ diameter and the other one 1/8’’ diameter. A BigSky/Quantel class 4 laser operating at 20 Hz and a range of energies (11-59 mJ/pulse) was used to produce a LIBS spark on targets within the TVAC chamber. Samples were shot for about 45s (~900 shots). The recording system was set-up to be triggered by the laser which allows to measure the travel time of the acoustic signal from the sample to the two microphones. Atmosphere conditions data. Acoustic data were collected with TVAC filled with 100% CO2 and at Mars-relevant pressure and temperatures which were varied around the values of 7 Torr and -200 C.

Abstract Acoustics is new on Mars: it allows the characterization of turbulence at smaller scales than previously possible within the lowest part of the Planetary Boundary Layer. Sound speed measurements, by the SuperCam instrument and its microphone onboard the NASA Perseverance rover, allow the retrieval of atmospheric temperatures at 0.77 m above the ground, at 3 Hz, with a ∼10 ms response time that is 20–100 times shorter than for typical thermocouple sensors used on Mars. Here we report on the first measurements of the sound speed‐derived temperature and its fluctuations near the surface. Data highlight large and rapid fluctuations up to ±7 K/s, whose amplitude over such a timescale has never been reported, nor predicted by atmospheric models. These fluctuations follow the daytime pattern of the turbulence and highlight occasional high amplitude events that are likely due to the conjunction of low thermal inertia and strong winds.

NASA’s InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission has operated a sophisticated suite of seismology and geophysics instruments on the surface of Mars since its arrival in 2018. On 18 February 2021, we attempted to detect the seismic and acoustic waves produced by the entry, descent and landing of the Perseverance rover using the sensors onboard the InSight lander. Similar observations have been made on Earth using data from both crewed 1,2 and uncrewed 3,4 spacecraft, and on the Moon during the Apollo era 5 , but never before on Mars or another planet. This was the only seismic event to occur on Mars since InSight began operations that had an a priori known and independently constrained timing and location. It therefore had the potential to be used as a calibration for other marsquakes recorded by InSight. Here we report that no signal from Perseverance’s entry, descent and landing is identifiable in the InSight data. Nonetheless, measurements made during the landing window enable us to place constraints on the distance–amplitude relationships used to predict the amplitude of seismic waves produced by planetary impacts and place in situ constraints on Martian impact seismic efficiency (the fraction of the impactor kinetic energy converted into seismic energy).

We requested HPC support to continue research on the seismic waves generated by impacts. We used the following codes: (1) the Hybrid Optimization Software Suite (HOSS), developed at LANL. HOSS is based on a combined Finite and Discrete Element Method (FDEM). New material models are developed for the sedimentary rocks. HOSS has been recently benchmarked to iSale and FLAG codes. SPECFEM3D is an open-source code developed since the last 90s. It won the Gordon Bell award for best performance in 2003, was finalist again in 2008 for a run at 0.16 petaflops on 149,784 cores on the ‘Jaguar’ Cray system at Oak Ridge National Laboratory. It also won the BULL Joseph Fourier supercomputing award in 2010.; SW4 is a 4th-order finite difference code developed at LLNL which is currently actively developed to handle complex 3D models and to be ported on future exascale platforms. We assessed our need to a total of 3.9M CPU-hrs for year 1 and and 3.1 M for year 2.