The shallow structure of Mars at the InSight landing site from inversion of ambient vibrations

Hobiger, Manuel; Hallo, Miroslav; Schmelzbach, Cédric; Stähler, Simon C.; Fäh, Donat; Giardini, Domenico; Golombek, M. P.; Clinton, John; Dahmen, Nikolaj; Zenhäusern, Géraldine; Knapmeyer‐Endrun, Brigitte; Carrasco, Sebastián; Charalambous, Constantinos; Hurst, Ken; Kedar, S.; Banerdt, W. B.

doi:10.1038/s41467-021-26957-7

Cited by 50 publications

(80 citation statements)

References 70 publications

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“…Crustal materials beneath these basalts are in general mechanically weak based on the lack of rocks in the ejecta of large fresh craters in the broad plains surrounding the landing site (Golombek et al., 2017). These two observation are consistent with the existence of a high seismic velocity layer beneath the lander representing the basalts between depths of about 75–175 m, and lower velocities beneath this layer representing the mechanically weak materials (Hobiger et al., 2021). Layered deposits are present in the central peaks of six impact craters that formed in the Late Amazonian‐Hesperian volcanic units to the northeast of the landing site.…”

Section: Discussionsupporting

confidence: 76%

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: Discussionsupporting

confidence: 76%

InSight Constraints on the Global Character of the Martian Crust

et al. 2022

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“…No new data was used in this study. The seismic velocity models are available in Hobiger et al (2021).…”

Section: Data Availability Statementmentioning

confidence: 99%

A Minimally Cemented Shallow Crust Beneath InSight

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et al. 2022

Geophysical Research Letters

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Cements in the Martian crust can have multiple origins, including ice frozen from liquid water or condensed from vapor, hydrated minerals formed in situ, or minerals precipitated from aqueous fluids (e.g., salts, carbonates, and sulfates). The presence, amount, and composition of ice and other mineral cements in the shallowest sections of the Martian crust have implications for robotic and human exploration of Mars, the processes that shape and shaped the surface, and the search for past or extant life. Research on these topics is central to determining if Mars ever supported life, to understand the climate history and processes, to understand Mars as a geological system, and to prepare for human exploration.Cementation affects and records geological processes. Cement can strengthen sediments (herein defined to include regolith and all other granular media layers) by creating stiffer contacts between particles. Cementation affects the permeability and porosity of sediments and fractured rocks, which impacts gas transport driven by atmospheric pressure changes (Morgan et al., 2021). Pores and fractures filled with ice or other mineral cement could confine any deeper liquid water, creating aquifers (Carr, 1979). Ground ice can promote weak explosive eruptions at rootless cones on lava flows (Brož et al., 2021) and may promote phreatomagmatic eruptions (Moitra et al., 2021). Cemented sediments are less prone to eolian and fluvial transport and erosion. The distribution of cements in the Martian sediments may record the accumulation and transport of volatiles in geologically recent times (Dundas et al., 2021). Cements may also preserve organic compounds diagnostic of past or present biological activity (Rivera-Valentín et al., 2020).Cementation impacts human exploration, and a primary motivation for the Mars Ice Mapper mission concept is to map ice in the shallowest crust (Davis & Haltigin, 2021). The presence of ice and hydrated minerals in shallow sediments and fractured rocks could provide a source of water for in situ resource utilization (Piqueux et al., 2019). Cementation-induced strengthening of sediments affects foundations used for engineering infrastructure (Kalapodis et al., 2020). Cemented sediments can be used as a construction material (Liu et al., 2021) and have prompted studies of a range of Mars simulants in preparation for future human missions (Karl et al., 2021).

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“…Yet, the non-uniqueness of geophysical observations in a single station is even worse for electromagnetic, specifically potential-based methods. Also, Hobiger et al (2021) demonstrated using InSight data that long-term observation of ambient vibrations at a single location can constrain even complicated subsurface structure, using geological context information, if available.…”

Section: Mission Perspectivesmentioning

confidence: 99%

“…On 5 May 2018, an Atlas V rocket finally launched the NASA InSight mission towards Mars, where it landed on 26 November 2018 and installed a seismometer on the surface in the weeks thereafter. This mission has since repeated many of the successes of a century of seismology within a good 3 years (Banerdt et al 2020;Giardini et al 2020;Lognonné, Banerdt, Pike, et al 2020;Knapmeyer-Endrun et al 2021;Khan, Ceylan, et al 2021;Stähler, Khan, et al 2021;Hobiger et al 2021), constraining the Martian interior structure from near surface to core.…”

Section: Introductionmentioning

confidence: 99%