Abstract One of the goals of the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission is to constrain the interior structure of Mars. We present a hierarchical transdimensional Bayesian approach to extract phase velocity dispersion and interior shear‐wave velocity (VS) models from a single seismogram. This method was adapted to Mars from a technique recently developed for Earth (Xu & Beghein, 2019, https://doi.org/10.1093/gji/ggz133). Monte Carlo Markov Chains seek an ensemble of one dimensional (1‐D) VS models between a source and a receiver that can explain the observed waveform. The models obtained are used to calculate the phase velocities of fundamental and higher modes at selected periods, and a subsequent analysis is performed to assess which modes were reliably measured. An advantage of our approach is that it can also fit unknown data noise, which reduces the risk of overfitting the data. In addition, uncertainties in the source parameters can be propagated, yielding more accurate model parameter uncertainties. In this study, we first present our technique and discuss the challenges stemming from using a single station to characterize both structure and the source and from the absence of a Mars reference model. We then demonstrate the method feasibility using the Mars Structure Service blind test data and our own synthetic data, which included realistic noise levels based on the noise recorded by InSight.

Seismic noise recorded at the surface of Mars has been monitored since February 2019, using the InSight seismometers.This noise can reach -200 dB and is 500 times lower than on Earth at night and it increases of 30 dB during the day. We analyze its polarization as a function of time and frequency in the band 0.03-1Hz. We use the degree of polarization to extract signals with stable polarization independent of their amplitude and type of polarization. We detect polarized signals at all frequencies and all times. Glitches correspond to linear polarized signals which are more abundant during the night. For signals with elliptical polarization, the ellipse is in the horizontal plane below 0.3 Hz (LF). Above 0.3 Hz (HF) and except in the evening, the ellipse is in the vertical plane and the major axis is tilted. While polarization azimuths are different in the two frequency bands, they both vary as a function of local hour and season. They are also correlated with wind direction, particularly during the daytime. We investigate possible aseismic and seismic origins of the polarized signals. Lander or tether noise can be discarded. Pressure fluctuations transported by wind may explain part of the HF polarization but not the tilt of the ellipse. This tilt can be obtained if the source is an acoustic emission coming from high altitude at critical angle. Finally, in the evening when the wind is low, the polarized signals may correspond to the seismic wavefield of the Mars background noise.

Measurements of ground compliance at the InSight landing site—describing the surface response to pressure loading—are obtained from seismic and meteorological data. Compliance observations show an increase with frequency indicating the presence of a stiffer rock layer beneath the exposed regolith. We performed a Markov chain Monte Carlo inversion to investigate the vertical profile of the elastic parameters down to 20 m below InSight. Compliance was inverted both freely and assuming prior knowledge of compaction in the regolith, and the limitations and strengths of the methods were assessed on the basis of theoretical considerations and synthetic tests. The inverted Young modulus exhibits an increase by a factor of 10–100 over the first 10–15 m, compatible with a structural discontinuity between 0.7 and 7 m. The proposed scheme can be used for joint inversion of other seismic, geological, or mechanical constraints to refine the resulting vertical section.

Mars’s seismic activity and noise have been monitored since January 2019 by the seismometer of the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander. At night, Mars is extremely quiet; seismic noise is about 500 times lower than Earth’s microseismic noise at periods between 4 s and 30 s. The recorded seismic noise increases during the day due to ground deformations induced by convective atmospheric vortices and ground-transferred wind-generated lander noise. Here we constrain properties of the crust beneath InSight, using signals from atmospheric vortices and from the hammering of InSight’s Heat Flow and Physical Properties (HP3) instrument, as well as the three largest Marsquakes detected as of September 2019. From receiver function analysis, we infer that the uppermost 8–11 km of the crust is highly altered and/or fractured. We measure the crustal diffusivity and intrinsic attenuation using multiscattering analysis and find that seismic attenuation is about three times larger than on the Moon, which suggests that the crust contains small amounts of volatiles. The crust beneath the InSight lander on Mars is altered or fractured to 8–11 km depth and may bear volatiles, according to an analysis of seismic noise and wave scattering recorded by InSight’s seismometer.

(1) Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, CNRS F-75005 Paris, France, (2) Laboratoire de Météorologie Dynamique (LMD/IPSL), Sorbonne Université, CNRS, École Polytechnique, École Normale Supérieure, Paris, France, (3) Institut Supérieur de l’Aéronautique et de l’Espace (ISAE-SUPAERO), Université de Toulouse, F-31000 Toulouse, France, (4) Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723, USA, (5) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 91109-8099 USA, (6) Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA, (7) NASA Goddard Space Flight Center, Greenbelt, MD, USA, (8) Laboratoire de Planétologie et Géologie-UMR CNRS 6112, Université de Nantes, 2 rue de la houssinière, BP 92208, 44322 Nantes Cedex 3, France.

InSight is the first planetary mission with a seismometer package, SEIS, since the Apollo Lunar Surface Experiments Package. SEIS is complimented by APSS, which has as a goal to document the atmospheric source of seismic noise and signals. Since June 2019, SEIS has been delivering 6 axis 20 sps continuous seismic data, a rate one order of magnitude larger originally planned. More than 50 events have been detected by the end of July 2019 but only three have amplitudes significantly above the SEIS instrument requirement. Two have clear and coherent arrivals of P and S waves, enabling location, diffusion/attenuation characterization and receiver function analysis. The event’s magnitudes are likely ≤ 3 and no clear surface waves nor deep interior phases have been identified. This suggests deep events with scattering along their final propagation paths and with large propagation differences as compared to Earth and Moon quakes. Most of the event’s detections are made possible due to the very low noise achieved by the instrument installation strategy and the very low VBB self-noise. Most of the SEIS signals have amplitudes of spectral densities in the 0.03-5Hz frequency bandwidth ranging from 10-10 m/s2/Hz1/2 to 5 10-9 m/s2/Hz1/2. The smallest noise levels occurs during the early night, with angstrom displacements or nano-radian tilts. This monitors the elastic and seismic interaction of a planetary surface with its atmosphere, illustrated not only by a wide range of SEIS signals correlated with pressure vortexes, dust devils or wind activity but also by modulation of resonances above 1 Hz, amplified by ultra-low velocity surface layers. After about one half of a Martian year, clear seasonal changes appear also in the noise, which will be discussed. One year after landing, the seismic noise is therefore better and better understood, and noise correction techniques begun to be implemented, either thanks to the APSS wind and pressure sensors, or by SEIS only data processing techniques. These data processing techniques open not only the possibility of better signal to noise ratio of the events, but are also used for various noise auto-correlation techniques as well as searches of long period signals. Noise and seismic signals on Mars are therefore completely different from what seismology encountered previously on Earth and Moon.

CORRELATING INSIGHT SEIS/APSS OBSERVATIONS ON MARS. N. A. Teanby1, R. Myhill1, A. Horleston1, J. Wookey1, W. T. Pike2, A. Stott2, C. Charalambous2, J. McClean2, T. Warren3, A. Spiga4, F. Forget4, E. Millour4, D. Banfield5, R. Lorenz6, C. Newman7, D. Viúdez Moreiras8, J. Pla-Garcia8,9, N. Murdoch10, D. Mimoun10, R. Garcia10, S. Kedar11, T. Kawamura12, B. Kenda12, P. Lognonné12, W. B. Banerdt11, and the InSight Team, 1University of Bristol (n.teanby@bristol.ac.uk), 2Imperial College, 3University of Oxford, 4LMD/IPSL, 5Cornell University, 6APL/JHU, 7Aeolis Research, 8INTA, 9SSI, 10ISAE-SUPAERO, 11JPL/Caltech, 12IPGP.

The 50th Lunar and Planetary Science Conference in The Woodlands, Texas, March 18–22, 2019.

InSight carries a sophisticated Meteorological Station and has observed a dust storm, baroclinic waves, thermal tides, gravity waves, undular bores, convective vortices (with dust cleaning), infrasound, clouds and aeolian change. We report on these.

A. Lucas B. Kenda, A. Mangeney, T. Kawamura, I. Daubar, O. Aharonson, M. Drilleau, A. Jacob, C. Hibert, A. Spiga, S. Rodriguez, R. Weber, P. Lognonné, Institut de Physique du Globe de Paris, Université Paris-Diderot, CNRS, Paris, France (lucas@ipgp.fr), Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, Department of Earth and Planetary Sciences, Center for Planetary Science, Weizmann Institute of Science, Rehovot, Israel, Institut de Physique du Globe de Strasbourg, EOST, Strasbourg, France, Laboratoire de Météorologie Dynamique, Sorbonne Université, Paris, France.

By the end of 2018, 42 years after the landing of the two Viking seismometers on Mars, InSight will deploy onto Mars’ surface the SEIS (Seismic Experiment for Internal Structure) instrument; a six-axes seismometer equipped with both a long-period three-axes Very Broad Band (VBB) instrument and a three-axes short-period (SP) instrument. These six sensors will cover a broad range of the seismic bandwidth, from 0.01 Hz to 50 Hz, with possible extension to longer periods. Data will be transmitted in the form of three continuous VBB components at 2 sample per second (sps), an estimation of the short period energy content from the SP at 1 sps and a continuous compound VBB/SP vertical axis at 10 sps. The continuous streams will be augmented by requested event data with sample rates from 20 to 100 sps. SEIS will improve upon the existing resolution of Viking’s Mars seismic monitoring by a factor of \(\sim 2500\) at 1 Hz and \(\sim 200\,000\) at 0.1 Hz. An additional major improvement is that, contrary to Viking, the seismometers will be deployed via a robotic arm directly onto Mars’ surface and will be protected against temperature and wind by highly efficient thermal and wind shielding. Based on existing knowledge of Mars, it is reasonable to infer a moment magnitude detection threshold of \(M_{{w}} \sim 3\) at \(40^{\circ}\) epicentral distance and a potential to detect several tens of quakes and about five impacts per year. In this paper, we first describe the science goals of the experiment and the rationale used to define its requirements. We then provide a detailed description of the hardware, from the sensors to the deployment system and associated performance, including transfer functions of the seismic sensors and temperature sensors. We conclude by describing the experiment ground segment, including data processing services, outreach and education networks and provide a description of the format to be used for future data distribution.

50th Lunar and Planetary Science Conference 2019 in The Woodlands, Texas, March 18–22, 2019.