Showing papers by "Institut supérieur de l'aéronautique et de l'espace published in 2022"

Marsquake Locations and 1‐D Seismic Models for Mars From InSight Data

Abstract: We present inversions for the structure of Mars using the first Martian seismic record collected by the InSight lander. We identified and used arrival times of direct, multiples, and depth phases of body waves, for 17 marsquakes to constrain the quake locations and the one-dimensional average interior structure of Mars. We found the marsquake hypocenters to be shallower than 40 km depth, most of them being located in the Cerberus Fossae graben system, which could be a source of marsquakes. Our results show a significant velocity jump between the upper and the lower part of the crust, interpreted as the transition between intrusive and extrusive rocks. The lower crust makes up a significant fraction of the crust, with seismic velocities compatible with those of mafic to ultramafic rocks. Additional constraints on the crustal thickness from previous seismic analyses, combined with modeling relying on gravity and topography measurements, yield constraints on the present-day thermochemical state of Mars and on its long-term history. Our most constrained inversion results indicate a present-day surface heat flux of 22 ± 1 mW/m2, a relatively hot mantle (potential temperature: 1740 ± 90 K) and a thick lithosphere (540 ± 120 km), associated with a lithospheric thermal gradient of 1.9 ± 0.3 K/km. These results are compatible with recent seismic studies using a reduced data set and different inversion approaches, confirming that Mars' potential mantle temperature was initially relatively cold (1780 ± 50 K) compared to that of its present-day state, and that its crust contains 10-12 times more heat-producing elements than the primitive mantle.

Infrasound From Large Earthquakes Recorded on a Network of Balloons in the Stratosphere

Abstract: The ground movements induced by seismic waves create acoustic waves propagating upward in the atmosphere, thus providing a practical solution to perform remote sensing of planetary interiors. However, a terrestrial demonstration of a seismic network based on balloon-carried pressure sensors has not been provided. Here we present the first detection of seismic infrasound from a large magnitude quake on a balloon network. We demonstrate that quake's properties and planet's internal structure can be probed from balloon-borne pressure records alone because these are generated by the ground movements at the planet surface below the balloon. Various seismic waves are identified, thus allowing us to infer the quake magnitude and location, as well as planetary internal structure. The mechanical resonances of balloon system are also observed. This study demonstrates the interest of planetary geophysical mission concepts based on seismic remote sensing with balloon platforms, and their interest to complement terrestrial seismic networks.

Martian free oscillations: Search in SEIS data and implications

Abstract: <p><strong>Introduction:</strong> For a single seismometer, the most effective techniques for studying deep structure use norma mode frequencies, which do not require knowledge of the source location. Past modeling (Lognonné et al., 1996, Lognonné, 2005) suggest that Normal mode spectral peaks from 5–20 mHz (sensitive to mantle structure) are expected to have amplitude larger than the SEIS requirement (10<sup>-9</sup> m/s<sup>2</sup>/Hz<sup>1/2</sup>) for moment larger than 2 10<sup>17</sup> Nm (equivalent magnitude ∼5.5).</p><p>Even for the event 1222 from May, 4, 2022, with an estimated magnitude of 5, the amplitude of normal modes is therefore low and their identification will be challenging in the data recorded by the SEIS VBB (Lognonné et al., 2019).</p><p><strong>Signal preprocessing:</strong> A very careful cleaning of the SEIS data is therefore requested, especially in order to remove most of the thermal glitches.  If not made, the spectra are dominated by these glitches. This pre-cleaning allow to converge to a corrected signal, which is robust with respect to deglitching parameters (Figure 1).</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.8676697b548267331482561/sdaolpUECMynit/2202CSPE&app=m&a=0&c=63a30253ab3fd8f5c39c5bb89af76ac1&ct=x&pn=gnp.elif&d=1" alt="" width="869" height="295"></p><p>Figure 1: (left) raw VBBZ data and (right) deglitched VBB data. Spectra from the night following the 1222 event.</p><p>The further detection of modes relies on the identification of spectral peaks in the Fourier amplitude or power spectra. However, close to the background noise level these spectral peaks can be either due to small harmonic signals contaminated by noise or due to the fortuitous constructive interference of noise. Besides, harmonic signals may be perceptive only during a limited portion of the analyzed time series which together with other larger amplitude signals further complicate the detection. For these reasons, we employ phase autocorrelation spectra (Schimmel et al., 2018) and conduct also a Phasor-Walkout analysis (e.g., Zürn and Rydelek, 1994, Schimmel et al., 2002) to search for and evidence normal modes.  In the following, we briefly summarize these strategies.</p><p><strong>Phase autocorrelation spectra.</strong> The identification of modes and determination of their frequency are usually based on the computation of the power or energy spectral density (PSD or ESD) which can be obtained through the Fourier Transform of differently defined autocorrelations. ESD can be computed for transient waveforms and equals the squared amplitude spectrum of the seismic recording while PSD is employed when the time series cannot be directly Fourier transformed due to infinite signal energy. Although the underlying autocorrelations are differently defined, they measure the self-similarity of the time series to reveal the spectral contents. In Schimmel et al. (2018), the conventional autocorrelations have been replaced by the phase cross-correlation (PCC; Schimmel ,1999) to show that phase autocorrelations provide an approach which can further aid the detection of modes. PCC is amplitude unbiased as it is based on envelope normalized analytic signals. Inherent to this, PCC is much less affected by outlying signals and supplies robust and independent spectra.</p><p><strong>Phasor-Walkout.</strong> The Phasor-Walkout approach (see  Zürn and Rydelek, 1994 for a review and further references) is a graphical representation of the Fourier Transform at a given test-frequency. It pictures the construction of the amplitude spectrum as a vector summation in the complex number space. In this summation, each vector corresponds to a time sample where the sample amplitude and time provide the length of the vector and its angle or phase. The sum of all vectors equals the Fourier amplitude of the spectrum at that frequency. The “walk” of the vectors in the complex number space is called Phasor-Walkout and permits to assess how the spectral amplitude has been build up. If the vectors point into similar directions then the summation becomes constructive while random directions produce a destructive summation which depends on the individual vector amplitudes.  For harmonic signals where the test-frequency matches the frequency of the oscillation the walk is straight while for pure random noise the Phasor-Walkout produces a random walk around its start point. Thus the qualitative inspection of Phasor-Walkout patterns may reveal the origin of spectral peaks.</p><p>Fig. 2 shows an example of phasor-walkouts at four different test frequencies.  Amplitude scale<br>is arbitrary and each color marks a two hours segment of the data. The walk starts at (0,0) which corresponds to the MQS event origin time. The top right panel shows a random walk while the other three panels contain linear walkouts of more than 6 hours.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.3fe856eb548266441482561/sdaolpUECMynit/2202CSPE&app=m&a=0&c=073aeaac956f5bc54b4e157db38126d9&ct=x&pn=gepj.elif&d=1" alt="" width="668" height="709"></p><p>Figure 2: walkout for 4 test frequencies.</p><p>Further work is required to present clean walkouts validating normal modes in the signal of the largest marsquake recorded by SEIS. When achieved, these frequencies might be inverted and will provide new constraints on the interior structure of the planet (Panning et al., 2017)</p><p><strong>References:</strong></p><p>Lognonné, P., J. Gagnepain-Beyneix, W.B. Banerdt, S.Cacho, J.F. Karczewski, M. Morand, An Ultra-Broad Band Seismometer on InterMarsnet, <em>Planetary Space Sciences</em>, <strong>44</strong>, 1237-1249, doi:10.1016/S0032-0633(96)00083-9, 1996.</p><p>Lognonné, P., Planetary seismology, <em>Annual Review in Earth Planet. Sci.,</em> 33 :19.1-19.34, doi :10.1146/annurev.earth.33.092203.122605, 2005.</p><p>Lognonné, P., Banerdt, W.B., Giardini, D. et al., SEIS: Insight’s Seismic Experiment for Internal Structure of Mars, Space Sci Rev, 215, 12, doi : 1007/s11214-018-0574-6 , 2019.</p><p>Nishikawa, Y., Lognonné, P., Kawamura, T., Spiga, A., Stutzmann, E., Schimmel, M., Bertrand, T., Forget, F., K. Kurita, K., Mars’ Background Free Oscillations, <em>Space Science Reviews</em> 215:13, doi: 10.1007/s11214-019-0579-9, 2019.</p><p>Panning, M.P., P.Lognonné, W. B. Banerdt et al., Planned products of the Mars Structure Service for the InSight mission, Mars, <em>Space Science review</em>, <strong>211</strong>, 611–650, doi: 10.1007/s11214-016-0317-5, 2017.</p><p>Schimmel M., Phase cross-correlations: design, comparisons and applications, <em>Bull. Seismol. Soc. Am.,</em> 89, 1366-1378, 1999.</p><p>Schimmel M., J. Waterhouse, M.D. Marques, D. Weinert, Circadian and ultradian rhythmicities in very premature neonates maintained in incubators , <em>Biol. Rhythm Res.</em>,  33, 83-111, doi:10.1076/brhm.33.1.83.1321 , 2002.</p><p>Schimmel, M., Stutzmann, E., Ventosa, S., Low-frequency ambient noise autocorrelations: Waveforms and normal modes, <em>Seismological Research Letters</em>, 89 (4), 1488-1496, doi: 10.1785/0220180027, 2018.</p><p>Zürn, W.; Rydelek, P., Revisiting the phasor-walkout method for detailed investigation of harmonic signals in time series, Surv. in geophys. 15, 409-431, 1994.</p>

First seismo-acoustic location and orbital imaging of recent impacts on Mars: constraints on atmosphere and interior structure and impact processes

Abstract: <p>The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander is providing an unprecedented set of high frequency records of ground deformations, pressure and wind at the surface of Mars. Seismic and acoustic waves from impacts have been observed by SEIS seismometer through the ground movements that they generate, and their sources as impacts have been confirmed with orbital images of newly appearing craters. Three impacts have been identified and located, and one additional seismic event is consistent with a date-constrained new impact. Several other events are currently being investigated as well. Arrival times and polarization of seismic and acoustic waves were used to estimate impact locations. These estimated locations were subsequently confirmed by orbital imaging of associated craters and temporal matches to the events times, with previous orbital images showing no craters. Crater dimensions and estimates of meteoroid trajectories from images allow us to understand and model the recorded seismograms. The precise source locations provided by impacts as compared to tectonic sources provide direct constraints on the structure of the martian interior. First arrival seismic waves confirm the previously determined crustal models, and the dispersion of trapped acoustic waves confirms the current models of sound speed and wind in the atmosphere. In addition, these observations provide the first ground-truth for distance-amplitude scaling relationships between impacts and the mechanical waves for Mars. They confirm the relationship between the seismic moment of impacts and the vertical impactor momentum, and demonstrate the capability of planetary seismology to constrain impact rates and internal structure of terrestrial planetary objects throughout the solar system.</p>

Machine learning and marsquakes: a tool to predict atmospheric-seismic noise for the NASA InSight mission

Abstract: SUMMARY The SEIS (seismic experiment for the interior structure of Mars) experiment on the NASA InSight mission has catalogued hundreds of marsquakes so far. However, the detectability of these events is controlled by the weather which generates noise on the seismometer. This affects the catalogue on both diurnal and seasonal scales. We propose to use machine learning methods to fit the wind, pressure and temperature data to the seismic energy recorded in the 0.4–1 and 2.2–2.6 Hz bandwidths to examine low- (LF) and high-frequency (HF) seismic event categories respectively. We implement Gaussian process regression and neural network models for this task. This approach provides the relationship between the atmospheric state and seismic energy. The obtained seismic energy estimate is used to calculate signal-to-noise ratios (SNR) of marsquakes for multiple bandwidths. We can then demonstrate the presence of LF energy above the noise level during several events predominantly categorized as HF, suggesting a continuum in event spectra distribution across the marsquake types. We introduce an algorithm to detect marsquakes based on the subtraction of the predicted noise from the observed data. This algorithm finds 39 previously undetected marsquakes, with another 40 possible candidates. Furthermore, an analysis of the detection algorithm’s variable threshold provides an empirical estimate of marsquake detectivity. This suggests that events producing the largest signal on the seismometer would be seen almost all the time, the median size signal event 45–50 per cent of the time and smallest signal events 5−20 per cent of the time.

Penetrometry in Microgravity- From Brie to Bennu

Abstract: <p>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.</p><p>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.</p>

Lateral variations of the Martian crustal thickness from the InSight data set

Abstract: <p>By using arrival times of body waves recorded by the very broadband seismometer SEIS from the InSight mission, 1D average models of the crust, mantle, and core of Mars have been inferred [1, 2, 3]. However, possible causes of seismic wavefield disturbances such as 3D structure, undeniably complexify the interpretation as a 1D radial model. Because the InSight lander and the origin of marsquakes are located close to the crustal dichotomy between the Southern and Northern hemispheres, significant lateral variations of the relief along the crust-mantle interface and the surface topography can potentially affect the seismic wave arrival times, especially for the multiples (PP, PPP, SS, SSS).              </p> <p>In contrast to investigations based on InSight seismic data, gravity and topography data allow one to address the question of lateral variations at global scale. However, the inversion of gravity and topography data is non-unique, in the sense that the latter generally assume constant values for the crust and mantle densities, and consider an average crustal thickness instead of lateral variations. We propose to use the crustal thickness range estimated below the InSight seismometer by [1] as an anchoring point.</p> <p>To characterize the Martian crustal thickness, we use a Bayesian approach. The marsquake locations (back azimuth, epicentral distance, and depth) and the average radial seismic velocity model of Mars are randomly sampled. Vp, Vs, and density are parameterized in terms of quantities that govern the thermo-chemical evolution of Mars, which accounts for 4.5 Gyr of planetary evolution [5, 6]. In addition to improving the model self-consistency compared to varying independently seismological parameters along the inversion process (Moho depth, seismic velocities, etc.), this geodynamical approach can also constrain the value of physical quantities that are not accessible to direct measurements, such as the rheology of the Martian mantle, and provides the entire history of the planet associated. For each model, a 3D crust is generated, following the approach developed in [4], using the observed gravity field and topography as constraints, enabling to apply body wave arrival time correction for each seismic phase. The models that do not match the crustal thickness range estimated below the InSight lander [1] are rejected.</p> <p>In addition to revealing the variability of the Martian global thickness maps, our approach shows that further insight into the value of the geodynamic quantities is gained by considering both seismic and gravity constraints on the present-day crustal thicknesses.</p> <p> </p> <p>References:</p> <p>[1] Knapmeyer-Endrun, B., et al., Science 373, 438-443 (2021)</p> <p>[2] Khan, A., et al., Science, 373, 434-438 (2021)</p> <p>[3] Stähler, S., et al., Science, 373, 443-448 (2021)</p> <p>[4] Wieczorek, M., et al., JGR Planets, 124, 1410-1432 (2019)</p> <p>[5] Drilleau, M., et al., JGR Planets, 226, 1615–1644 (2019)</p> <p>[6] Samuel, H., et al., Nature, 569, 523–527 (2019)</p> <p> </p>

Analysis of General Shape Optimization Problems in Nonlinear Acoustics

Abstract: Abstract In various biomedical applications, precise focusing of nonlinear ultrasonic waves is crucial for efficiency and safety of the involved procedures. This work analyzes a class of shape optimization problems constrained by general quasi-linear acoustic wave equations that arise in high-intensity focused ultrasound (HIFU) applications. Within our theoretical framework, the Westervelt and Kuznetsov equations of nonlinear acoustics are obtained as particular cases. The quadratic gradient nonlinearity, specific to the Kuznetsov equation, requires special attention throughout. To prove the existence of the Eulerian shape derivative, we successively study the local well-posedness and regularity of the forward problem, uniformly with respect to shape variations, and prove that it does not degenerate under the hypothesis of small initial and boundary data. Additionally, we prove Hölder-continuity of the acoustic potential with respect to domain deformations. We then derive and analyze the corresponding adjoint problems for several different cost functionals of practical interest and conclude with the expressions of well-defined shape derivatives.

Computational Modeling of Turbulent Spray Combustion Process Using RANS and Large-Eddy Simulations

Abstract: Computational fluid dynamics is applied to reproduce the characteristics of the liquid methanol burner presented by the National Institute of Standards and Technology (NIST). Reynolds avera...

What can we learn from an in-situ accelerometer during surface interactions?

Abstract: <p>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].</p> <p>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). </p> <p> </p> <p><img src="" alt="" width="748" height="418" /></p> <p>Figure 1. The  granular materials used in the experimental trials</p> <p> </p> <p>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 (z<sub>drop</sub>), the collision velocity (v<sub>c</sub>), the collision duration (t<sub>stop</sub>) and the peak acceleration (a<sub>peak</sub>). 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 (t<sub>peak</sub>), 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 .</p> <p><img src="" alt="" width="785" height="525" /></p> <p>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.</p> <p> </p> <p><img src="" alt="" width="858" height="483" /></p> <p>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).</p> <p><strong>Acknowledgements</strong></p> <p>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.</p> <p><strong>References:</strong></p> <p>[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).</p> <p>[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)</p> <p>[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.</p> <p>[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.</p> <p>[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)</p> <p>[6] Michel, P., et al. 2022, The MMX rover: performing in situ surface investigations on Phobos. Earth Planets Space 74, 2</p> <p>[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.</p> <p>[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.</p> <p>[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.</p> <p>[10] Clark et al., 2013, Granular impact dynamics: Fluctuations at short time-scales, AIP Conference Proceedings 1542, 445-448</p> <p>[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</p> <p> </p>