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Impact-Seismic Investigations of the InSight Mission

Daubar, Ingrid and Kanamori, Hiroo (2018) Impact-Seismic Investigations of the InSight Mission. Space Science Reviews, 214 (12). Art. No. 132. ISSN 0038-6308. http://resolver.caltech.edu/CaltechAUTHORS:20190104-094912398

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Abstract

Impact investigations will be an important aspect of the InSight mission. One of the scientific goals of the mission is a measurement of the current impact rate at Mars. Impacts will additionally inform the major goal of investigating the interior structure of Mars. In this paper, we review the current state of knowledge about seismic signals from impacts on the Earth, Moon, and laboratory experiments. We describe the generalized physical models that can be used to explain these signals. A discussion of the appropriate source time function for impacts is presented, along with spectral characteristics including the cutoff frequency and its dependence on impact momentum. Estimates of the seismic efficiency (ratio between seismic and impact energies) vary widely. Our preferred value for the seismic efficiency at Mars is 5×10^(−4), which we recommend using until we can measure it during the InSight mission, when seismic moments are not used directly. Effects of the material properties at the impact point and at the seismometer location are considered. We also discuss the processes by which airbursts and acoustic waves emanate from bolides, and the feasibility of detecting such signals. We then consider the case of impacts on Mars. A review is given of the current knowledge of present-day cratering on Mars: the current impact rate, characteristics of those impactors such as velocity and directions, and the morphologies of the craters those impactors create. Several methods of scaling crater size to impact energy are presented. The Martian atmosphere, although thin, will cause fragmentation of impactors, with implications for the resulting seismic signals. We also benchmark several different seismic modeling codes to be used in analysis of impact detections, and those codes are used to explore the seismic amplitude of impact-induced signals as a function of distance from the impact site. We predict a measurement of the current impact flux will be possible within the timeframe of the prime mission (one Mars year) with the detection of ∼ a few to several tens of impacts. However, the error bars on these predictions are large. Specific to the InSight mission, we list discriminators of seismic signals from impacts that will be used to distinguish them from marsquakes. We describe the role of the InSight Impacts Science Theme Group during mission operations, including a plan for possible night-time meteor imaging. The impacts detected by these methods during the InSight mission will be used to improve interior structure models, measure the seismic efficiency, and calculate the size frequency distribution of current impacts.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1007/s11214-018-0562-xDOIArticle
https://rdcu.be/bfoj9PublisherFree ReadCube access
ORCID:
AuthorORCID
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 2018 Springer Nature B.V. Received: 5 April 2018; Accepted: 13 November 2018; Published online: 6 December 2018. We are grateful to Jay Melosh and an unnamed reviewer for thoughtful and helpful comments. We appreciate the hard work of the engineering and operations teams who are making the InSight mission possible. Elizabeth Barrett provided valuable input. Thank you to Matthew Siegler for helping to address a reviewer comment. A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. French co-authors thank the support of the French Space Agency CNES as well as ANR SIMARS. IPGP coauthors (IPGP contribution number 3988) also received support from the UnivEarth Labex at Sorbonne Paris Cité (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02). N. Teanby and J. Wookey are funded by the UK Space Agency. Swiss co-authors recognize the support of the (1) Swiss National Science Foundation and French Agence Nationale de la Recherche (SNF-ANR project 157133 “Seismology on Mars”) and (2) Swiss State Secretariat for Education, Research and Innovation (SEFRI project “MarsQuake Service—Preparatory Phase”). We gratefully acknowledge the developers of the iSALE hydrocode. A portion of this work was performed using HPC resources of CINES (Centre Informatique National de l’Enseignement Supérieur) under the allocation A0030407341 made by GENCI (Grand Equipement National de Calcul Intensif). KM research is fully supported by the Australian Government (project numbers DE180100584 and DP180100661). This is InSight Contribution Number 47.
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Agence Nationale pour la Recherche (ANR)ANR-10-LABX-0023
Agence Nationale pour la Recherche (ANR)ANR-11-IDEX-0005-02
United Kingdom Space Agency (UKSA)UNSPECIFIED
Swiss National Science Foundation (SNSF)157133
Swiss State Secretariat for EducationUNSPECIFIED
Centre Informatique National de l’Enseignement SupérieurA0030407341
Australian Research CouncilDE180100584
Australian Research CouncilDP180100661
Subject Keywords:InSight; Mars; Impact cratering; Seismology
Record Number:CaltechAUTHORS:20190104-094912398
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190104-094912398
Official Citation:Daubar, I., Lognonné, P., Teanby, N.A. et al. Space Sci Rev (2018) 214: 132. https://doi.org/10.1007/s11214-018-0562-x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92087
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:04 Jan 2019 18:01
Last Modified:04 Jan 2019 18:01

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