A Comodulation Analysis of Atmospheric Energy Injection into the Ground Motion at InSight, Mars

Constantinos Charalambous*, Anna C Horleston, Alexander E. Stott, W. T. Pike, J.B. McClean, T Warren, A. Spiga, D Banfield, R. Garcia, John Clinton, Simon C. Stähler, S Navarro, P. Lognonné, John-Robert Scholz, Taichi Kawamura, Martin van Driel, Maren Böse, Savas Ceylan, Amir Khan, Guenolé Orhand-MainsantL. M. Sotomayor, Naomi Murdoch, D. Giardini, W. B. Banerdt

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

Seismic observations involve signals that can be easily masked by noise injection. For the NASA Mars lander InSight, the atmosphere is a significant noise contributor, impeding the identification of seismic events for two-thirds of a Martian day. While the noise is below that seen at even the quietest sites on Earth, the amplitude of seismic signals on Mars is also considerably lower, requiring an understanding and quantification of environmental injection at unprecedented levels. Mars’ ground and atmosphere are a continuously coupled seismic system, and although atmospheric functions are of distinct origins, the superposition of these noise contributions is poorly understood, making separation a challenging task. We present a novel method for partitioning the observed signal into seismic and environmental contributions. Atmospheric pressure and wind fluctuations are shown to exhibit temporal cross-frequency coupling across multiple bands, injecting noise that is neither random nor coherent. We investigate this through comodulation, quantifying the synchrony of the seismic motion, wind and pressure signals. By working in the time-frequency domain, we discriminate between the different origins of underlying processes and determine the site's environmental sensitivity. Our method aims to create a virtual vault at InSight's landing site on Mars, shielding the seismometers with effective postprocessing in lieu of a physical vault. This allows us to describe the environmental and seismic signals over a sequence of sols, to quantify the wind and pressure injection and estimate the seismic content of possible marsquakes with a signal-to-noise ratio that can be quantified in terms of environmental independence. Finally, we exploit the relationship between the comodulated signals to identify their sources.
Original languageEnglish
Article numbere2020JE006538
Number of pages35
JournalJournal of Geophysical Research: Planets
Volume126
Issue number4
Early online date8 Feb 2021
DOIs
Publication statusE-pub ahead of print - 8 Feb 2021

Bibliographical note

Funding Information:
The authors would like to thank the Editor-in-Chief Prof. Laurent Montesi, Adam Ringler and another anonymous reviewer who provided thorough and helpful reviews that have improved this manuscript. We would also like to thank Andrea Christophi for constructive criticism of the manuscript. We acknowledge NASA, UK Space Agency, CNES, their partner agencies and Institutions (UKSA, IC, SSO, DLR, JPL, IPGP-CNRS, ETHZ, MPS-MPG) and the flight operations team at JPL, SISMOC, MSDS, IRIS-DMC, and PDS for acquiring and providing InSight data, including SEED SEIS data.

Funding Information:
SEIS raw data are in “” (2019) with 10.18715/SEIS.INSIGHT.XB_2016 . The seismic and atmospheric measurement data presented here are also publicly available in InSight Mars SEIS Data Service ( 2019a ) SEIS Bundle with 10.17189/1517570 , APSS TWINS Bundle (Mora, 2019b ) with 10.17189/1518950 and APSS PS Bundle (Mora, 2019a ) with 10.17189/1518939 through the Planetary Data System (PDS) Geosciences node, but also through the Incorporated Research Institutions for Seismology (IRIS) Data Management Center under network code XB and through the Data center of Institut de Physique du Globe, Paris ( http://seis-insight.eu ). The InSight seismic event catalog (InSight Marsquake Service, 2020 ) is available from the IPGP Datacenter and IRIS‐DMC. Codes for processing comodulation as used in this analysis have been put on GitHub available at https://github.com/ConstantinosCharalambous/comodulation in Charalambous ( 2020a ) with 10.5281/zenodo.4292720 . Processed data and sample data sets to run the code is available in Charalambous ( 2020b ) with 10.18715/ipgp.2020.Khw87roo . French coauthors acknowledge the support of CNES and of Agence Nationale de la Recherche under grant ANR‐19‐CE31‐0008‐08. This is InSight Contribution Number 170. InSight Mars SEIS Data Service together with IPGP, JPL, CNES, ETHZ, ICL, MPS, ISAE‐Supaero, LPG, MFSC

Publisher Copyright:
© 2021. The Authors.

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