Journal: Journal of Geophysical Research: Planets

Abbreviation

J. geophys. res. Planets.

Publisher

Wiley

Journal Volumes

ISSN

0148-0227
2169-9097
2169-9100

Description

Filters

2023 - 20243
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Publications 1 - 3 of 3
  • Focal Mechanism Determination of Event S1222a and Implications for Tectonics Near the Dichotomy Boundary in Southern Elysium Planitia, Mars
    Item type: Journal Article
    Maguire, Ross; Lekić, Vedran; Kim, Doyeon; et al. (2023)
    Journal of Geophysical Research: Planets
    On 4 May 2022 the InSight seismometer SEIS-VBB recorded the largest marsquake ever observed, S1222a, with an initial magnitude estimate of (Figure presented.) 4.6. Understanding the depth and source properties of this event has important implications for the nature of tectonic activity on Mars. Located ∼37° to the southeast of InSight, S1222a is one of the few non-impact marsquakes that exhibits prominent surface waves. We use waveform modeling of body waves (P and S) and surface waves (Rayleigh and Love) to constrain the focal mechanism, assuming a double-couple source, and find that S1222a likely resulted from reverse faulting in the crust (source depth near 22 km). We estimate the scalar moment to be 2.5 × 1015–3.5 × 1015 Nm (magnitude MW 4.2–4.3). Our results suggest active compressional tectonics near the dichotomy boundary on Mars, likely due to thermal contraction from planetary cooling.
  • Mantle Mineralogy of Reduced Sub-Earths Exoplanets and Exo-Mercuries
    Item type: Journal Article
    Cioria, Camilla; Mitri, Giuseppe; Connolly, James Alexander Denis; et al. (2024)
    Journal of Geophysical Research: Planets
    The mineralogy of planetary mantles formed under reducing conditions, as documented in the inner regions of the solar system, is not well constrained. We present thermodynamic models of mineral assemblages that would constitute the mantles of exo-Mercuries. We investigated reduced materials such as enstatite chondrites, CH, and CB chondrites, and aubrites, as precursor bulk compositions in phase equilibrium modeling. The resulting isochemical phase diagram sections indicate that dominant phases in these reduced mantles would be pyroxenes rather than olivine, contrasting with the olivine-rich mantles found within Earth, Mars, and Venus. The pyroxene abundances in the modeled mantles assemblages depend on the silica content shown by precursor materials. The silica abundance in the mantle is closely related to Si abundance in the core, particularly in reduced environments. In addition, we propose that pyroxene-rich mantles exhibit more vigorous convective and tectonic activity than olivine-rich mantles, given that pyroxene-rich mantles would have lower viscosity and a lower solidus temperature (Ts).
  • Tectono-Magmatic Evolution of Asymmetric Coronae on Venus: Topographic Classification and 3D Thermo-Mechanical Modeling
    Item type: Journal Article
    Gülcher, Anna J.P.; Yu, Ting-Ying; Gerya, Taras V. (2023)
    Journal of Geophysical Research: Planets
    Venus is the only other Earth-sized planet in the Solar System but it does not exhibit evidence of plate tectonics that dominates geological processes on Earth. Surface deformation on Venus is mainly driven by mantle convection and plume-lithosphere interactions, likely represented by the widespread development of the circular volcano-tectonic features known as coronae. Here, we present a joint study of mission data analysis and 3D modeling of asymmetric coronae on Venus. We systematically analyze 155 of the largest coronae on Venus in terms of surface topography and morphology. We establish that 75% of those coronae are radially asymmetric, and further sub-categorize them based on their adjacent topography. This analysis reveals that many asymmetric coronae are positioned at a topographic transition between a lowland and plateau (termed topographic margin). With state-of-the-art 3D numerical models, we investigate the physical processes behind plume-margin interactions on Venus. We find that several tectonic styles may be responsible for asymmetric coronae at topographic margins, including lowland-sided subduction, plateau-sided lithospheric dripping, and an embedded plume. The gradient in lithospheric strength across the topographic margin controls these tectonic styles, and larger gradients enhance lithospheric resurfacing and the lifetime of the coronae. We also find that the density increase associated with the basalt-to-eclogite phase change provides the extra negative gravitational force required for downgoing crust to be recycled into the mantle. The models presented in this study reproduce a wide set of asymmetrical corona features found on Venus and suggest that they are generally more long-lived than symmetric coronae.
Publications 1 - 3 of 3