Displays

How to cite: Pike, W. T., Banerdt, W., Smrekar, S., Lognonné, P., Giardini, D., Banfield, D., Dehant, V., Folkner, W., Golombek, M., Johnson, C., Russell, C., Spiga, A., and Spohn, T.: Results From the Insight Mission After a Year and a Half on Mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22031, https://doi.org/10.5194/egusphere-egu2020-22031, 2020.

NASA’s InSight mission deployed the Seismic Experiment for Interior Structure (SEIS) instrument on Mars, with the goal of detecting, discriminating, characterizing and locating the seismicity of Mars and study its internal structure, composition and dynamics. 44 years since the first attempt by the Viking missions, SEIS has revealed that Mars is seismically active. So far, the Marsquake Service (MQS) has identified 365 events that cannot be explained by local atmospheric or lander-induced vibrations, and are interpreted as marsquakes. We identify two families of marsquakes: (i) 35 events of magnitude MW=3-4, dominantly long period in nature, located below the crust and with waves traveling inside the mantle, and (ii) 330 high-frequency events of smaller magnitude and of closer distance, with waves trapped in the crust, exciting an ambient resonance at 2.4Hz. Two long period events with larger SNR and excellent P and S waves occurred on Sol 173 and 235, visible both on the VBB and the SP channels; the location of these events has been determined at distances of 26°-30° towards the East, close to the Cerberus Fossae tectonic system. Over ten additional long period events show consistent body-wave phases interpreted as P and S phases and can be aligned with distance using models of P and S propagation. Marsquakes have spectral characteristics similar to seismicity observed on the Earth and Moon. From the spectral characteristics of the recorded seismicity and the event distance, we constrain attenuation in the crust and mantle, and find indications of a potential low S-wave-velocity layer in the upper mantle. In contrast, the high-frequency events provide important constraints on the elastic and anelastic properties of the crust. The first seismic observations on Mars deliver key new knowledge on the internal structure, composition and dynamics of the red planet, opening a new era for planetary seismology. Here we review the seismicity detected so far on Mars, including location, distance, magnitude, magnitude-frequency distribution, tectonic context and possible seismic sources.

How to cite: Giardini, D., Lognonne, P., Banerdt, B., Boese, M., Ceylan, S., Clinton, J., van Driel, M., Garcia, R., Kawamura, T., Khan, A., Knapmeyer, M., Panning, M., Perrin, C., Pike, T., and Stähler, S.: Seismicity of Mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20437, https://doi.org/10.5194/egusphere-egu2020-20437, 2020.

We analyze the sequence of seismic events of different types as recorded by the SEIS instrument of the InSight mission. After several weeks without any detection, event counts started to increase at the end of May 2019. The majority of recorded events belongs to the class of 2.4 Hz events, which prominently excite a continuously observed natural resonance frequency.

After a sudden onset of seismic detections by the end of May 2019 (about sol 180, L_S≈32°), especially the combined event rate of the High Frequency, Very High Frequency, and 2.4 Hz family of events increased from 3.6 events/sol in June 2019 to more than 9 events/sol until late August 2019, i.e. increased by a factor of about 3.

Estimating event rates as if events are the result of a constant-rate Poisson process leads to contradictions with the statistical properties of those, either in the cumulative event count or in the lag time distribution. These contradictions can be overcome by assuming a step-wise increase of the event rate.

Any deviation from a purely random occurrence of quakes, in both time and space, requires a mechanism to suppress or support the source process. The seismic activity of the Moon is mainly controlled by tidal deformation, at least in terms of source time. What controls the event rate of Martian high frequency events is currently elusive.

How to cite: Knapmeyer, M., Stähler, S. C., van Driel, M., Clinton, J. F., Banerdt, W. B., Böse, M., Ceylan, S., Charalambous, C., Garcia, R. F., Horleston, A., Kawamura, T., Khan, A., Lognonne, P., Panning, M., Giardini, D., Pike, W. T., Scholz, J.-R., and Weber, R. C.: Is there a Seasonality of the Martian Seismic Event Rate?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18429, https://doi.org/10.5194/egusphere-egu2020-18429, 2020.

On the 26th of November 2018, NASA’s InSight lander successfully touched down on the Martian ground in Elysium Planitia. The lander transported among other instruments a single three-component broadband seismometer to measure seismic events and subsequently determine the seismic activity level and eventually the internal structure of Mars. In this study we focus on characterizing the source mechanisms of the highest-quality marsquakes detected so far: The events with highest SNR occurred on sols 173 (S0173a, May 23rd 2019) and 235 (S0235b, July 27th 2019) with Mw > 3.5, showing clearly polarized P and S waves. The InSight MarsQuake Service has estimated their distances to be around 27 degrees, nearby the Cerberus Fossae Graben system. Two more events, S0183a and S0325b have less clear body wave phases and locations, but are also interpreted to be related to it.

We have developed a grid-search based method to fit synthetic waveforms to the observed first arriving P and S wave trains. The four source parameters we invert for in this study are the three unique orientation angles of the source mechanism, strike (φ), dip (δ) and rake (λ), and the depth of the event. Synthetic seismograms are generated by computing Green’s functions based on the epicentral distance determined by the InSight MarsQuake Service (MQS) and radially symmetric velocity models. These Green’s function are then convolved with a source time function including an estimated global body wave attenuation to obtain realistic seismograms. 

The two high-quality event recordings originating from the Cerberus Fossae (CF) fault system were analyzed. Multiple velocity models, frequency bands and window lengths around the arriving phases were used to explore the non-uniqueness in the inverse problem of the inherently ambiguous single-station data. We found that using plausible structural models based on geophysical modeling, the first 10-15 seconds of the waveforms can be fit, constraining the source mechanism and depth, but that the estimation of the uncertainty remains challenging.

How to cite: Brinkman, N., Jacob, A., Stähler, S., Schmelzbach, C., Fuji, N., Perrin, C., Batov, A., Böse, M., Clinton, J., van Driel, M., Drilleau, M., Giardini, D., Gudkova, T., Robertsson, J. O. A., and Banerdt, W. B. and the MQS frontline and review team: Source mechanism solutions of low frequency Martian events based on body wave coda from a single seismic station, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18020, https://doi.org/10.5194/egusphere-egu2020-18020, 2020.

The Heat Flow and Physical Properties Package HP³ onboard the Nasa InSight mission has been on the surface of Mars for more than one Earth year. The instrument's primary goal is to measure Mars' surface heat flow through measuring the geothermal gradient and the thermal condunctivity at depths between 3 and 5m. To get to depth, the package includes a penetrator nicknamed the "Mole"  equipped with sensors to precisely measure the thermal conductivity. The Mole tows a tether with printed temperature sensors;  a device to measure the length of the tether towed and a tiltmeter will help to track the path of the Mole and the tether. Progress of the Mole has been stymied by difficulties of digging into the regolith. The Mole functions as a mechanical diode with an internal hammer mechanism that drives it forward. Recoil is balanced mostly by internal masses but a remaining 3 to 5N has to be absorbed by hull friction. The Mole was designed to work in cohesionless sand but at the InSight landing a cohesive duricrust of at least 7cm thickness but possibly 20cm thick was found. Upon initial penetration to 35cm depth, the Mole punched a hole about 6cm wide and 7cm deep into the duricrust, leaving more than a fourth of its length without hull friction.  It is widely agreed that the lack of friction is the reason for the failure to penetrate further. The HP³ team has since used the robotic arm with its scoop to pin the Mole to the wall of the hole and helped it penetrate further to almost 40cm. The initial penetration rate of the Mole has been used to estimate a penetration resistance of 300kPa. Attempts to crush the duricrust a few cm away from the pit have been unsuccessful from which a lower bound to the compressive strength of 350kPa is estimated.  Analysis of the slope of the steep walls of the hole gave a lower bound to cohesion of 10kPa. As for thermal properties, a measurement of the thermal conductivity of the regolith with the Mole thermal sensors resulted in 0.045 Wm^-1K^-1.  The value is considerably uncertain because part of the Mole having contact to air.  The HP³ radiometer has been monitoring the surface temperature next to the lander and a thermal model fitted to the data give a regolith thermal inertia of  189 ± 10 J m^-2 K^-1 s^-1/2. With best estimates of heat capacity and density, this corresponds to a thermal conductivity of 0.045 Wm^-1K^-1, consistent with the above measurement using the Mole. The data can be fitted well with a homogeneous soil model, but observations of Phobos eclipses in March 2019 indicate that there possibly is a thin top layer of lower thermal conductivity. A model with a top 5 mm layer of 0.02 Wm-1K-1 above a half-space of 0.05 Wm-1K-1 matches the amplitudes of both the diurnal and eclipse temperature curves. Another set of eclipses will occur in April 2020.

How to cite: Spohn, T., Grott, M., Müller, N., Knollenberg, J., Krause, C., Hudson, T., Deen, R., Marteau, E., Golombek, M., Hurst, K., Piqueux, S., Smrekar, S., Thomas, A. L., Fantinati, C., Lichtenheldt, R., and Wippermann, T.: Mars Regolith Properties as Constrained from HP3 Mole Operations and Thermal Measurements , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9163, https://doi.org/10.5194/egusphere-egu2020-9163, 2020.

Measurements of near-surface winds on Mars are vital to understand momentum, heat, and gas exchange (e.g. water vapor, methane) at the surface; to interpret surface aeolian features, from wind streaks to dunes; to understand the conditions required for raising dust from the surface; to combine with other observations of atmospheric phenomena such as baroclinic waves, convective vortices, and clouds; to test and improve atmospheric models, which may then be used with greater confidence for other locations and epochs; to provide ground truth for Entry-Descent-Landing, the Mars2020 helicopter, and Ascent Vehicles; and finally, to help quantify the conditions that will be faced by future human explorers of Mars.

Despite this, however, good wind datasets are very rare for Mars. The Viking Landers provided valuable information on seasonal and diurnal variations in wind speed and direction, including the impact of dust storms, but recorded high frequency winds only a small portion of the time. Mars Pathfinder lasted only a few months on the surface and recorded wind directions but could not produce calibrated wind speeds. Phoenix similarly had a short lifetime and only measured intermittently at low temporal resolution and accuracy, although provided both wind speed and direction. Spirit and Opportunity carried no wind sensors at all. The ongoing Mars Science Laboratory mission’s Curiosity Rover carried the first wind sensor to operate in a region of strong topography (Gale Crater); however, electronic noise and damage upon landing resulted in many data gaps and biases in the wind dataset, and the wind sensor was permanently lost after fewer than three Mars years due to further damage.

InSight carries the TWINS wind sensor, consisting of two booms facing in opposite directions. The wind speed and direction at any time is obtained by selecting the boom with the least interference by lander components or heating. By the time of this presentation, InSight should have measured wind continuously at ~1.2m above the surface for over 500 Mars sols (nearly three-quarters of a Mars year), with the majority of this dataset available at a frequency of 1Hz.

We will present the InSight wind dataset and describe how it has already helped Mars scientists to make progress in a range of fields. These include understanding the origins of aeolian features and inferring thresholds for sand motion or dust lifting, as well as quantifying the impact of topography and dust loading on modifying the regional circulation. Comparison with the winds predicted by atmospheric models has shown areas of disagreement, pointing to places where a different model setup or boundary condition (e.g. resolution, roughness map) may be needed, or where the model’s parameterizations of sub-grid scale physical processes (e.g. vertical mixing) need to be improved. Finally, given InSight’s proximity to the Curiosity Rover, we will show how winds in some seasons provide information on the regional flow before it reaches Gale Crater, and hence aid in interpreting Curiosity’s more complex wind dataset.

How to cite: Newman, C. and the TWINS and InSight Teams: The winds of Mars: Why InSight wind data are so valuable and what they tell us, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20295, https://doi.org/10.5194/egusphere-egu2020-20295, 2020.

InSight is the first Mars surface mission that includes a magnetometer, and one of the first discoveries made by the InSight FluxGate (IFG) magnetometer is the ultra-low-frequency (ULF) waves, or magnetic pulsations, on the Martian surface. By studying magnetic pulsations and transient signatures in more than six months of IFG data, we find that the morphologies of these two types of perturbations have considerable variations from their counterparts on the Earth, reflecting the fundamental differences between the magnetospheres with and without a global magnetic field. The most noticeable ULF waves are the continuous pulsations (Pc) occurring at around midnight and with wave periods of the order of 100 sec, or in the Pc 4 frequency band when the terminology of terrestrial magnetic pulsations is used. Broadband pulsations at Pc 5 frequencies (i.e., a few mHz) have also been observed. Comparisons with lander activities and InSight’s Temperature and Wind for InSight Subsystem (TWINS) data confirm that the observed magnetic pulsations are not caused by tremors of the lander. Simultaneous observations by MAVEN in the solar wind and InSight on Mars indicate that the upstream waves in front of Mars bow shock can hardly reach the dayside surface, leading to a dearth of magnetic pulsations in the daytime. In addition, solar wind discontinuities or transient events can induce noticeable surface magnetic responses only in the nightside, suggesting that the magnetic pileup region and ionosphere can effectively shield external magnetic disturbances. MAVEN observations also help identify sources of magnetic pulsations seen on the Martian surface. While the low-frequency, broad-band Pc 5 pulsations may be excited by the oscillations on the flanks of the induced magnetosphere associated with solar wind variations or the Kelvin-Helmholtz instability, there is a strong indication that the nightside Pc 4 pulsations on the surface originate from the compressional oscillations in the magnetotail. Different from the flow-generated fast mode waves in the terrestrial magnetotail, the fast mode in the Martian magnetotail could travel toward the planet without substantial coupling to the Alfvén mode. The Mars-propagating fast mode experiences little reflection from the ionosphere and can produce surface magnetic pulsations at low latitudes on the nightside. These first findings of magnetic pulsations and transients on the Martian surface not only reveal the origins and propagation of magnetic signals from the outer space but also help determine the source model for the magnetic sounding of Mars' interior.

How to cite: Chi, P., Russell, C., Joy, S., Yu, Y., Banfield, D., Fillingim, M., Ma, Y., Smrekar, S., and Banerdt, W.: Magnetic Pulsations and Transients on Martian Surface, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11771, https://doi.org/10.5194/egusphere-egu2020-11771, 2020.

After a 6-month flight to Mars and a successful landing, InSight has deployed SEIS … its seismometer designed to sit on the Martian surface. The goal of this mission is to investigate the dynamics of Martian seismic activity and understand the processes that shaped the Red Planet.

SEIS InSight has engaged a generation of school kids, teens and students which, like scientists, follow the mission live. The data from InSight offers a chance to leverage existing Seismometers in Schools networks to allow a large and growing number of students to interact with seismic data recorded on Mars as soon as it is available on Earth.  Students in these international networks have experience with seismic data and software and are primed to engage with this NASA Discovery mission.

Seismic data in the classroom has provided both a hook for inquiry with real data as well as a common language for international collaboration.

These resources input innovative educational strategies acculturating pupils in the acquisition, processing, display and exploration of seismic and weather data.

A very large school network (middle and high schools) share resources and activities using InSight data. Networks are preparing lessons, software, web tools, data viewers, and other resources to allow students to explore and interrogate shaking on Mars to better understand the heart of the planet.

In this presentation, we will show all the practical activities and all the different tools created for the kids, teens and students. This work has been developed by teachers, educators, and scientists in international cooperation, and can be found on dedicated websites.

How to cite: Berenguer, J. L., Bravo, T., Sauron-Sornette, A., and Stevenson, J.: Engaging Schools with InSight Data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6826, https://doi.org/10.5194/egusphere-egu2020-6826, 2020.

About one year after the successful deployment of the InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) very-broadband seismometer on the Martian surface and the identification of several hundreds of seismic events in the current InSight catalogue, we revise the pre-launch magnitude relations in Böse et al. (2018) to account for the seismic and noise characteristics observed on Mars. The data collected so far indicate that (1) marsquakes are characterized by energy between ~0.1-10Hz; (2) neither surface-wave nor secondary phase arrivals have yet been identified; and (3) a class of high-frequency events exists that are visible mainly as an increased excitation of the 2.4Hz mode. In view of these observations, we up-date scaling relations for the spectral and body-wave magnitudes, and introduce a new magnitude scale for high-frequency events. We use these relations to determine that the magnitudes of events in the current InSight catalogue range between 1.0 and 4.0.

How to cite: Böse, M., Stähler, S., Giardini, D., Ceylan, S., Clinton, J., van Driel, M., Knapmeyer, M., Lognonné, P., and Banerdt, B.: Updated Magnitude Scales for Mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13034, https://doi.org/10.5194/egusphere-egu2020-13034, 2020.

We present an updated estimate of the seismic activity rate of Mars after seven months of high-quality recording of the InSight SEIS instrument. The instrument has been deployed fully on Sol 60 (February 2, 2019) and has been recording with excellent performance since then. The first distant marsquake was observed on Sol 105 (March 14), the first local event on Sol 128 (April 7). From then until early January 2020 (Sol 400), 23 likely events and another 13 candidate events have been observed. Due to a strong diurnal variation in background noise and the generally low magnitude of the activity (compared to Earth), events have been observed only in few low-noise periods of the day. The change of seasons varied the duration of these low-noise periods over the mission, with a magnitude and time-dependent effect on detectability of events and the quantitative estimation of event rates and moment release.

We present a statistical analysis of the global seismic activity level based on a preliminary seismic magnitude model, weighted by the temporal evolution of the ambient noise over half a Martian year. The resulting number of events smaller magnitude 3 is roughly consistent with the pre-mission estimate of Golombek (1992) and the medium model of Knapmeyer et al. (2006), however, as of now, there is a statistically significant lack of events above magnitude 3.5. This hints at a distribution that is skewed towards smaller events, compared to terrestrial global averages.

How to cite: Stähler, S. C., Knapmeyer, M., Giardini, D., Clinton, J., Pike, T., Lognonné, P., Panning, M., Böse, M., Ceylan, S., Charalambous, C., van Driel, M., Horleston, A., Kawamura, T., Kedar, S., Khan, A., Scholz, J.-R., and Banerdt, B.: Seismic activity rate of Mars, based on 420 Sols of InSight data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13482, https://doi.org/10.5194/egusphere-egu2020-13482, 2020.

InSight landed on Mars in late November 2018, and the SEIS seismometer package was fully deployed by February 2019. By January 2020, SEIS continues to exceed performance expectations in terms of observed minimum noise. The Marsquake Service (MQS) has been setup to create and curate a seismicity catalogue for Mars over the lifetime of the InSight mission. Seismic waveforms are downloaded daily from the station and are analysed and processed by the MarsQuake Service, with the goal of detecting seismic vibrations not due to local ambient sources. To this end, every precaution is applied to eliminate possible non-seismic sources, such as noise induced by atmospheric phenomena, lander vibrations and orbiter activity. At the date of submission, we have detected 365 events, of different quality and SNR levels. Signal amplitudes remain small and signal can generally only be detected at night. Some events show only low-frequency waves in the 1-10 sec band, others have a high-frequency content up to several Hz, and others have a more broad-band character. A special class of events involves the excitation of a very prominent ambient vibration at 2.4Hz. Despite the scattered nature of the energy, in many cases, distinct phases can be inferred in the waveforms. Body wave character, and back-azimuth, can only be confirmed for 3 broadband events so far.  The MQS approach for determining distances from broadband events identifies phases as mantle P and S-phases and uses an a priori set of several thousand martian models, derived from geophysical, mineralogical and orbital constraints. High frequency events are currently located assuming phases are trapped crustal Pg and Sg and using a simple crustal layer. The MQS works in conjunction with the Mars Structural Service (MSS) on building and adopting updated models. The MQS consists of an international team of seismologists that screen incoming data to identify and characterise any seismicity. In this presentation, we present the MQS, demonstrate how we detect and characterise marsquakes, and describe the challenges we face dealing with the Martian dataset.

How to cite: Clinton, J., Giardini, D., Ceylan, S., van Driel, M., Stähler, S., Banerdt, B., Böse, M., Charalambous, C., Euchner, F., Horleston, A., Kawamura, T., Garcia, R., Kedar, S., Khan, A., Lognonnne, P., Mainsant, G., Panning, M., Pike, T., Scholz, J.-R., and Smrekar, S. and the ERP Gurus: Monitoring Seismicity on Mars - the Marsquake Service for InSight, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11577, https://doi.org/10.5194/egusphere-egu2020-11577, 2020.

InSight landed on Mars in late November 2018, and the SEIS package, which consists of one short period and one very broadband sensor, was deployed on the surface shortly after. The data returned by the InSight is monitored in a timely manner by the Marsquake Service (MQS), a ground segment support group of InSight that has been set up to establish and maintain the seismicity catalogue. The MQS has at least one member on duty who routinely checks the data for any type of seismic signals. All suspicious signals are then communicated to the InSight team after evaluation.

To date, MQS has identified more than 365 events which are classified into two general families as high and low frequency, with each family having unique features in terms of their energy content. The most distinct quakes detected so far belong to the low frequency family that occurred on Sol 173 and 235, and have clear P and S-wave arrivals that reveal a distance around 30 degrees east of the lander, pointing the region in the vicinity of Cerberus Fossae. In addition to the signals of seismic origin, the SEIS data contain features that originate from other sources such as atmospheric effects or electronics. Part of these non-seismic observations may resemble quakes which may lead to wrong interpretations, and therefore require careful analysis.

Here, we show examples of signals of both seismic and non-seismic origins. We describe the characteristics of these observations in time and frequency domains in order to give an overview of martian data content.

How to cite: Ceylan, S., Clinton, J. F., Giardini, D., Böse, M., van Driel, M., Euchner, F., Horleston, A., Kawamura, T., Khan, A., Orhand-Mainsant, G., Scholz, J.-R., Stähler, S., Charalambous, C., Banerdt, W. B., Garcia, R. F., Kedar, S., Lognonné, P., Panning, M., Pike, T., and Smrekar, S. E.: Overview of observed seismic signals on Mars, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19482, https://doi.org/10.5194/egusphere-egu2020-19482, 2020.

NASA’s InSight mission arrived on Mars in November 2018 and deployed the first very broad-band seismometer, SEIS, on the planet’s surface. SEIS has been collecting data continuously since early February 2019, by now recording more than 400 events of different types. InSight aims at enhancing our understanding of the internal structure and dynamics of Mars, including better constraints on its crustal thickness. Various models based on topography and gravity observed from the orbit currently vary in average crustal thickness from 30 km to more than 100 km, with important implications for Mars’ thermal evolution, and the partitioning of silicates and heat-producing elements between different layers of Mars.

We present P-to-S and S-to-P receiver functions, which are available for 4 and 3 marsquakes, respectively, up to now. Out of all of the marsquakes recorded to date, these are the only ones with clear enough P- or S-arrivals not dominated by scattering to make them suitable for the analysis. All of the quakes are located at comparatively small epicentral distances, between 25° and 40°. We observe three consistent phases within the first 10 seconds of the P-to-S receiver functions. The S-to-P receiver functions also show a consistent first phase. Later arrivals are harder to pinpoint, which could be due to the comparatively shallow incidence of the S-waves at the considered distances, which prevents the generation of converted waves. Identification of later multiple phases in the P-to-S receiver functions likewise remains inconclusive. To obtain better constraints on velocity, we also calculated apparent velocity curves from the P-to-S receiver functions, but these provide meaningful results for only one event so far, implying a large uncertainty. Due to difficulties in clearly identifying multiples, the receiver functions can currently be explained by either two crustal layers and a thin (25-30 km) crust or three crustal layers and a thicker (40-45 km) crust at the landing site. This model range already improves the present constraints by providing a new maximum value of less than 70 km for the average crustal thickness. Information from noise autocorrelations as a complementary method, identification of P-reverberations and S-precursors in the event recordings, and more extensive modeling, ultimately including 3D-effects, are considered to further our understanding of the waveforms and tighten the constraints on the crust.

How to cite: Knapmeyer-Endrun, B., Bissig, F., Compaire, N., Garcia, R., Joshi, R., Khan, A., Kim, D., Lekic, V., Margerin, L., Panning, M., Schimmel, M., Schmerr, N., Stutzmann, E., Tauzin, B., Tharimena, S., Stähler, S., Davis, P., Pinot, B., and Scholz, J.-R. and the InSight crustal structure team: First seismic constraints on the Martian crust – receiver functions for InSight, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22525, https://doi.org/10.5194/egusphere-egu2020-22525, 2020.

For Earth and Moon, the seismic observation data is the most direct and effective means to detect their internal structure. However, due to the long distance between Mars and Earth and the harsh observation conditions on Mars, the exploration of Martian velocity structure model is a very challenging task. The InSight lander deployed the first seismic observation instrument SEIS (Seismic Experiment for Internal Structure) on the Mars’ surface after its successful landing on Mars on November 26, 2018. In this study, we performed horizontal-to-vertical spectral ratio (HVSR) and polarization analysis of three component VBB seismic waveforms recorded by the SEIS station released on the IRIS website. We are trying to constrain the thickness of the Martian regolith at the landing site of InSight from the SEIS data. The VBB ambient noise data we used are in HHV/HHU/HHW channels of ELYSE station in 30 Martian days. These data are predominantly ambient noise data caused by wind effects and do not contain any known marsquake data. We found that the HVSR curves from nearly all released data show two distinct peaks at 11.9 Hz and 24.5 Hz, respectively. Furthermore, we conducted particle motion and polarization analysis on these data in various frequency bands, which indicate that the ground motion at the highest peak show linearly polarized and vertically incident motion with a fixed azimuth. This could be explained by the S-wave resonance of the Martian regolith at the InSight landing site caused by the wave motion source from the wind induced motion of the lander. Using the possible S-wave velocity of the Martian regolith proposed by previous studies and the peak frequencies of the HVSR results in this study, thickness of the Martian regolith at the InSight landing site was obtained that is smaller than the pre-evaluated thickness (3~5 m) for the InSight mission.

How to cite: Xiao, W. and Wang, Y.: Study on the Structural Characteristics of Martian Regolith by Ambient Noise Data from SEIS Observation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20940, https://doi.org/10.5194/egusphere-egu2020-20940, 2020.

Investigating the interior structure of Mars is important to study not only its past and present state and future evolution, but also the formation and evolution of the Earth and solar system. Seismological methods played import roles in the study of the Earth and Moon’s interior. The first mission about Martian seismology began in 1976, but no seismic events were convincingly detected during the observation. The InSight Spacecraft landed on Mars on November 26, 2018 in Elysium Planitia and installed the first seismometer on Mars. It will provide the in situ observation of interior structure and seismic activity of Mars for the first time. In this study, we perform numerical modelling of seismic wave propagation in whole-mars models by solving the seismic wave equations using a hybrid pseudospectral and finite difference method on staggered grid. Firstly, based on the Martian internal models derived from geochemical analysis (Sohl and Spohn, 1997), we present numerical simulations of seismic wave propagation in the whole Mars models. The generation and propagation of various seismic phases in the whole Mars models are shown by synthetic seismograms and wavefield snapshots. We analyze the effects of crustal thickness and depth of core mantle boundary on seismic wave propagation. Then based on the present model of Martian crustal thickness (Wieczorek and Zuber, 2004), we simulate seismic wave propagation in laterally heterogeneous Martian crust and analyze the influence of lateral heterogeneity on global seismic wave propagation. Multiple reflections and conversions of seismic waves and their constructive interference occurred inside the low-velocity Martian crust form reverberating wave trains. Thickness of Martian crust has strong effect on the propagation of multiple surface reflections and surface waves. Seismic reflections from core-mantle boundary can be clearly identified from the calculated transverse component seismogram.

How to cite: Wang, Y., Xiao, W., and Deng, D.: Numerical Modeling of Global Seismic Wave Propagation in the Whole Mars Models and Effect of Lateral Crustal Variation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20959, https://doi.org/10.5194/egusphere-egu2020-20959, 2020.

 NASA InSight (the Interior Exploration using Geodesy and Heat Transport) has placed the first broadband seismometer (SEIS) on the Martian surface and now continuously monitoring Martian seismic activity. Since the first detection of a marsquake in March 2019, SEIS detected more than 200 marsquakes and Mars has been revealed to be a seismically active planet. The dataset can now be used to perform the seismic investigation of the Mars interior and interpret this in a comparative manner by referring to the examples from the Earth and the Moon.

In this study, we investigate the seismic attenuation on Mars and compare this with the Earth and the Moon. Attenuation can be described as a combination of inelastic absorption and elastic diffusion of energy. Such properties will give important constraints on the composition of the Mars interior and also its thermal state. Another interesting aspect will be to discuss the water content with respect to the attenuation. Given the large variety of water content for the Earth, the Moon and Mars, the attenuation feature will be likely to differ significantly between these planets and satellite. Here we use the seismic dataset obtained by InSight SEIS and construct a 1D structure of seismic attenuation on Mars. Then we refer to the values obtained for the Earth and the Moon to discuss the possible implication on their differences and similarities.

　The presentation aims to summarize the results from different approaches taken by the authors. The approach includes; 1) spectral analyses of seismic signals and spectral decay fitting, 2) seismic coda analyses with coda rise time and decay, 3) numerical coda simulation with diffusion theory on seismic energy. With these approaches we will be constraining seismic quality factor Q and diffusivity D for different depth range. Different approaches have sensitivities to different depth and prarameters and we aim to provide our view on the martian attenuation and diffusion to date by summarizing the obtained results.

How to cite: Kawamura, T., Margerin, L., Drilleau, M., Ménina, S., Lognonné, P., Schmerr, N. C., Stäehler, S., Driel, M. V., and Banerdt, B.: Investigation of Mars Seismic Attenuation Using InSight SEIS Data. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16469, https://doi.org/10.5194/egusphere-egu2020-16469, 2020.

Mars atmospheric pressure variations induce ground displacements through elastic deformations. The various sensors of INSIGHT mission were designed in order to be able to understand and correct these ground deformations induced by atmospheric effects. Particular efforts were done on one side to avoid direct pressure and wind effects on the seismometer, and on the other side to have a high performance pressure sensor operating in the same frequency range than the seismometer.
As a consequence of the high performances of both instruments, their very efficient protection systems against direct atmospheric disturbances, and the low Mars background seismic noise, INSIGHT mission is opening a new science domain for which the ground displacements can be used to perform atmospheric science.
This study presents an analysis of pressure and seismic signals and their relations. After a short description of the pressure and seismic sensors deployed by INSIGHT, we present an analysis of these signals as a function of local time at INSIGHT location.
Then, the background and event like coherent signals between Pressure and seismometer sensors are interpreted in terms of various atmospheric excitations and induced  ground deformation processes. Different methods to remove the pressure effects recorded by SEIS sensors are presented, and their efficiency is estimated. Finally, we demonstrate that the pressure and ground deformations measurements can be used to decipher between various atmospheric excitation types (meteorological pressure variations, acoustic and gravity waves)  and characterize these. Effects of the local sub-surface structure are also suggested by the data analysis.

How to cite: Garcia, R. F., Kenda, B., Drilleau, M., Spiga, A., Kawamura, T., Lognonné, P. H., Murdoch, N., Compaire, N., Banfield, D., Widmer-Schnidrig, R., Orhand-Mainsant, G., and Banerdt, W. B.: Pressure effects on SEIS-INSIGHT instrument, improvement of seismic records and characterization of gravity waves from ground displacements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20748, https://doi.org/10.5194/egusphere-egu2020-20748, 2020.

The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed in western Elysium Planitia on November 26, 2018. Because of its stationary position and a multi-instrument package, InSight offers the unique opportunity of detecting changes induced by aeolian activity and constraining the atmospheric conditions responsible for particle motion.

In this work, we present the most significant changes from aeolian activity as detected by the InSight lander during its first 400 Martian days of operations. We will show that particle entrainment by wind activity around InSight is a subtle process and report simultaneous measurements observed across multiple instruments. The changes observed are episodic and are seen correlated with excursions in both seismic and magnetic signals, which will be discussed further. Our observations show that all aeolian movements are consistent with the passage of deep convective vortices between noon to 3 pm local time. These vortices may be the primary initiators for aeolian transportation at InSight, inducing episodic particulate motion of grains up to 3 mm in diameter.

How to cite: Charalambous, C., Baker, M., Golombek, M., McClean, J., Pike, T., Spiga, A., Stott, A., Ansan, V., Weitz, C., Grant, J., Warner, N., Rodriguez, S., Lorenz, R., Mittelholz, A., Johnson, C., Maki, J., Lemmon, M., Banks, M., Murdoch, N., and Daubar, I. and the Co-authors: Aeolian Changes at the Insight Landing Site on Mars: Multi-instrument Observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12178, https://doi.org/10.5194/egusphere-egu2020-12178, 2020.

The InSight instrumentation for atmospheric science combines high frequency, high accuracy and continuity. This makes InSight a mission particularly suitable for studies of the variability in the Planetary Boundary Layer (PBL) of Mars -- all the more since this topic is of direct interest for quake detectability given that turbulence is the main contributor to atmosphere-induced seismic signal. For the strong daytime buoyancy-driven PBL convection, InSight significantly extends the statistics of dust-devil-like convective vortices and turbulent wind gustiness, both of which are of strong interest for aeolian science. For the moderate nighttime shear-induced PBL convection, InSight enables to explore phenomena and variability left unexplored by previous in-situ measurements on Mars. In both daytime and nighttime environments, how the gravity waves and infrasound signals discovered by InSight are being guided within the PBL is also a central topic to InSight's atmospheric investigations, with the tantalizing possibility to identify possible sources for those phenomena. InSight has been operating at the surface of Mars since 18 months, thus the seasonal evolution of the many phenomena occurring in the PBL will be an emphasis of this report. Comparisons with turbulence-resolving modeling such as Large-Eddy Simulations will be also discussed.

How to cite: Spiga, A., Murdoch, N., Banfield, D., Lorenz, R., Newman, C., Pla-Garcia, J., Garcia, R., Lognonné, P., Martire, L., and Navarro, S. and the the InSight team: Daytime and nighttime turbulence on Mars monitored by InSight, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21327, https://doi.org/10.5194/egusphere-egu2020-21327, 2020.

The InSight ultra-sensitive broadband seismometer package (SEIS) was installed on the Martian surface with the goal to study the seismicity on Mars and the deep interior of the Planet. A second surface-based instrument, the heat flow and physical properties package HP³, was placed on the Martian ground about 1.1 m away from SEIS. HP³ includes a self-hammering probe called the ‘mole’ to measure the heat coming from Mars' interior at shallow depth to reveal the planet's thermal history. While SEIS was designed to study the deep structure of Mars, seismic signals such as the hammering ‘noise’ as well as ambient and other instrument-generated vibrations allow us to investigate the shallow subsurface. The resultant near-surface elastic property models provide additional information to interpret the SEIS data and allow extracting unique geotechnical information on the Martian regolith.

The seismic signals recorded during HP³ mole operations provide information about the mole attitude and health as well as shed light on the near-surface, despite the fact that the HP³ mole continues to have difficulty penetrating below 40 cm (one mole length). The seismic investigation of the HP³ hammering signals, however, was not originally planned during mission design and hence faced several technical challenges. For example, the anti-aliasing filters of the seismic-data acquisition chain were adapted when recording the mole hammering to allow recovering information above the nominal Nyquist frequency. In addition, the independently operating SEIS, HP³ and lander clocks had to be correlated more frequently than in normal operation to enable high-precision timing.

To date, the analysis of the hammering signals allowed us to constrain the bulk P-wave velocity of the volume between the mole tip and SEIS (top 30 cm) to around 120 m/s. This low velocity value is compatible with laboratory tests performed on Martian regolith analogs with a density of around 1500 kg/m³. Furthermore, the SEIS leveling system resonances, seismic recordings of atmospheric pressure signals, HP³ housekeeping data, and imagery provide additional constraints to establish a first seismic model of the shallow (topmost meters) subsurface at the landing site.

How to cite: Schmelzbach, C., Brinkman, N., Sollberger, D., Kedar, S., Grott, M., Andersson, F., Robertsson, J., van Driel, M., Stähler, S., ten Pierick, J., Hudson, T., Hurst, K., Drilleau, M., Kenda, B., Garcia, R., Murdoch, N., Giardini, D., Lognonne, P., Pike, W. T., and Spohn, T. and the InSight SEIS and Near Surface Team: Seismic investigations of the Martian near-surface at the InSight landing site, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20481, https://doi.org/10.5194/egusphere-egu2020-20481, 2020.

The martian magnetic field oscillates at frequencies from once per day to periods of only 100s of seconds. The interior of Mars is electrically conducting, and the time-varying magnetic fields create induced currents in the electrically conducting subsurface of Mars. The diurnal periods are little affected by the interior conductivity, but at periods shorter than about 1000 sec, the reflection of the magnetic wave energy is strong, and the vertical component of the oscillating magnetic field approaches zero as the frequency increases. Electromagnetic waves at the shorter (<1000s) periods are produced by the nighttime currents such as those flowing on and within the Mars magnetotail. These fluctuations are weak in the vertical component of the waves associated with the restriction of the currents to flow horizontally as the wave period grows shorter. This phenomenon is also seen on Earth and has been well characterized there. The measure of the attenuation of the vertical component is referred to as the skin depth. The attenuation observed at the InSight landing site is consistent with a skin depth of 3.4 km for the expected conductivity of terrestrial seawater. We have not seen any variation of this skin depth with season. These observations are consistent with the many manifestations of the occasional presence of water on or near the surface of Mars and strengthen the case for permanent water in the soil only several kilometers beneath the surface.

How to cite: Yu, Y., Russell, C., Fillingim, M., and Banerdt, W.: Evidence for a Wet Martian Interior from Magnetic Sounding with the InSight Magnetometer, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2238, https://doi.org/10.5194/egusphere-egu2020-2238, 2020.