Seismology on Mars: An analysis of direct, reflected, and converted seismic body waves with implications for interior structure

Durán, Cecilia; Khan, A.; Ceylan, Savas; Zenhäusern, Géraldine; Stähler, Simon C.; Clinton, John; Giardini, Domenico

doi:10.1016/j.pepi.2022.106851

Cited by 68 publications

(141 citation statements)

References 65 publications

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“…In this work, we construct global models of the crust using both the two-and three-layer crustal thickness estimates beneath the InSight lander from Knapmeyer-Endrun et al (2021), which are 20 ± 5 km and 39 ± 8 km, respectively. These values are largely consistent with the analysis of Durán et al (2022), who obtained respective ranges of 22-27 and 37-47 km. In the following subsection, we first describe three different density models of the crust that we will consider in our modeling.…”

Section: Global Crustal Thickness Modelingsupporting

confidence: 91%

“…Consistent with the PP receiver functions, the S receiver functions also required a three-layer crust to fit the precursor phases. A re-analysis of the InSight seismic data by Durán et al (2022) that included P receiver functions of seven events has also confirmed a three-layer structure with major seismic discontinuities in the depth ranges of 8-13 km, 22-27 km, and 37-47 km.…”

Section: Tablementioning

confidence: 77%

“…Analyses of the InSight seismic data indicate that there are three major seismic discontinuities beneath the lander where the seismic velocity abruptly increases. In addition to the crust‐mantle interface at a depth of about 39 km, two intracrustal discontinuities are observed at depths near 8 and 20 km (Durán et al., 2022; Kim, Lekić, et al., 2021; Knapmeyer‐Endrun et al., 2021; Lognonné et al., 2020). There are many possible explanations for the existence of large‐scale layering within the crust, and most of these involve a change in crustal density.…”

Section: Discussionmentioning

confidence: 99%

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InSight Constraints on the Global Character of the Martian Crust

et al. 2022

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Analyses of seismic data from the InSight mission have provided the first in situ constraints on the thickness of the crust of Mars. These crustal thickness constraints are currently limited to beneath the lander that is located in the northern lowlands, and we use gravity and topography data to construct global crustal thickness models that satisfy the seismic data. These models consider a range of possible mantle and core density profiles, a range of crustal densities, a low-density surface layer, and the possibility that the crustal density of the northern lowlands is greater than that of the southern highlands. Using the preferred InSight three-layer seismic model of the crust, the average crustal thickness of the planet is found to lie between 30 and 72 km. Depending on the choice of the upper mantle density, the maximum permissible density of the northern lowlands and southern highlands crust is constrained to be between 2,850 and 3,100 kg m −3 . These crustal densities are lower than typical Martian basaltic materials and are consistent with a crust that is on average more felsic than the materials found at the surface. We argue that a substantial portion of the crust of Mars is a primary crust that formed during the initial differentiation of the planet. Various hypotheses for the origin of the observed intracrustal seisimic layers are assessed, with our preferred interpretation including thick volcanic deposits, ejecta from the Utopia basin, porosity closure, and differentiation products of a Borealis impact melt sheet. Plain Language SummaryThe crust, mantle and core are the three major geochemical layers that make up a planet. Before NASA's InSight mission, the thickness of the crust of Mars was inferred using indirect techniques, including analyses of gravity data collected from orbit and the composition of surface rocks. Estimates for the average thickness using these techniques spanned the range from 27 to 118 km. Analyses of data collected by the InSight seismometer have provided us with the first direct seismic measurement of the thickness of the crust, but this measurement is only for beneath the lander that is located in the northern lowlands where the crust is expected to be thinner than average. In this work, gravity and topography data are used to construct global crustal thickness models that satisfy the new seismic constraints. The average crustal thickness is found to be somewhere between 32 and 70 km, and the average density of the crust can be no larger than 3,100 kg m −3 . This bulk crustal density is lower than most typical Martian WIECZOREK ET AL.

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Section: Global Crustal Thickness Modelingsupporting

confidence: 91%

Section: Tablementioning

confidence: 77%

Section: Discussionmentioning

confidence: 99%

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InSight Constraints on the Global Character of the Martian Crust

et al. 2022

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“…Furthermore, due to the uncertainty of the source location, Martian studies to date have relied on differential times (e.g. Durán et al, 2022;Drilleau et al, 2021) for which ellipticity corrections are expected to be even less significant.…”

Section: Ellipticity Corrections On Marsmentioning

confidence: 99%

A Re-examination of Ellipticity Corrections for Seismic Phases

Russell¹,

Rudge²,

Irving³

et al. 2022

Preprint

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The Earth's ellipticity of figure has an effect on the travel times of seismic waves over teleseismic distances. Tables of ellipticity corrections and coefficients have been used by seismologists for several decades, however due to the increasing variety and complexity of seismic phases in use, current tables of ellipticity coefficients are now obsolete and incomplete. We present a Python package, EllipticiPy, for the calculation of ellipticity corrections that removes the dependence on pre-calculated coefficients at discrete source depth and epicentral distances. EllipticiPy also facilitates the calculation of ellipticity corrections on other planetary bodies. When applied to both Earth and Mars, the magnitudes of ellipticity corrections are on the order of single seconds and are significant for some seismic studies on Earth but remain negligible on Mars due to other greater sources of uncertainty.

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“…• While first layered models of the crust and mantle, including the radius of the core were obtained by InSight using a single station only (Durán et al 2022;Khan, Ceylan, et al 2021;Knapmeyer-Endrun et al 2021; Tharsis (Horleston et al 2022) suggests that much more small seismicity could be present there, unobservable from InSight's location. At the same time, Plesa et al (2021) showed that geodynamical models predict significant lateral variations in seismic wave speed, potentially higher than on Earth.…”

Section: Potential Scientific Goalsmentioning

confidence: 99%