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"Elkins-Tanton, Linda T."
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Volcanism and global environmental change
\"Covering a key connection between geological processes and life on Earth, this multidisciplinary volume describes the effects of volcanism on the environment by combining present-day observations of volcanism and environmental changes with information from past eruptions preserved in the geologic record. The book discusses the origins, features and timing of volumetrically large volcanic eruptions; methods for assessing gas and tephra release in the modern day and the palaeo-record; and the impacts of volcanic gases and aerosols on the environment, from ozone depletion to mass extinctions. The significant advances that have been made in recent years in quantifying and understanding the impacts of present and past volcanic eruptions are presented and review chapters are included, making this a valuable book for academic researchers and graduate students in volcanology, climate science, palaeontology, atmospheric chemistry, and igneous petrology.\"-- Provided by publisher.
Book
Magma oceans as a critical stage in the tectonic development of rocky planets
Magma oceans are a common result of the high degree of heating that occurs during planet formation. It is thought that almost all of the large rocky bodies in the Solar System went through at least one magma ocean phase. In this paper, we review some of the ways in which magma ocean models for the Earth, Moon and Mars match present-day observations of mantle reservoirs, internal structure and primordial crusts, and then we present new calculations for the oxidation state of the mantle produced during the magma ocean phase. The crystallization of magma oceans probably leads to a massive mantle overturn that may set up a stably stratified mantle. This may lead to significant delays or total prevention of plate tectonics on some planets. We review recent models that may help alleviate the mantle stability issue and lead to earlier onset of plate tectonics.
This article is part of a discussion meeting issue 'Earth dynamics and the development of plate tectonics'.
Journal Article
A Post‐Launch Summary of the Science of NASA's Psyche Mission
Astronomical observations indicate that asteroid (16) Psyche is a large, high‐density (likely >3,400 kg·m−3), metal‐rich (30–55 vol. %) asteroid. Psyche may be remnant core material or it could be a primordial, undifferentiated metal‐rich object. We discuss the science objectives of the upcoming Psyche mission, which will employ three instruments (the Magnetometer, Multispectral Imager, and Gamma‐Ray and Neutron Spectrometer) and will use Doppler tracking of the spacecraft to explore the asteroid. This mission will shed light on the nature and origins of metal‐rich objects in the solar system and beyond, including the cores of the terrestrial planets. Plain Language Summary Asteroid (16) Psyche is the largest known metal‐rich asteroid and is a relic of the building blocks of the planets from the early solar system. We hypothesize that it is either an exposed metallic core of an asteroid or unmelted metal‐rich material. NASA's Psyche mission, launched in October 2023, aims to explore Psyche to understand its formation and evolution. The Psyche spacecraft carries three instruments and will use its radio antenna to study Psyche's magnetic field, surface composition, and interior structure. The Psyche mission offers a historic opportunity to study the processes that led to the formation of the metallic cores of planets. Key Points The Psyche mission will explore the solar system's largest likely metal‐rich asteroid, (16) Psyche Exploration of Psyche offers a historic opportunity to explore small body planetary differentiation and core formation The Psyche spacecraft will study Psyche using imaging, nuclear spectroscopy, magnetometry, and gravity measurements
Journal Article
Crystals stirred up: 1. Direct numerical simulations of crystal settling in nondilute magmatic suspensions
This is the first paper in a two‐part series examining the fluid dynamics of crystal settling and flotation in the lunar magma ocean. A key challenge in constraining solidification processes is determining the ability of individual crystals to decouple from vigorous thermal convection and settle out or float. The goal of this paper is to develop a computational methodology capable of capturing the complex solid‐fluid interactions that determine settling and flotation. In the second paper, we use this computational approach to explore the conditions under which plagioclase feldspar would be able to buoyantly float and form the earliest crust on the Moon. The direct numerical method described in this paper relies on a fictitious domain approach and captures solid‐body motion in 2D and 3D with little overhead beyond single fluid calculations. The two main innovations of our numerical implementation of a fictitious domain approach are an analytical quadrature scheme, which increases accuracy and reduces computational expense, and the derivation of a multibody collision scheme. Advantages of this approach over previous simulations of crystal‐bearing magmatic suspensions include the following: (1) we fully resolve the two‐way interaction between fluid and solid phases, implying that crystals are not only passively advected in an ambient flow field but are also actively driving flow, and (2) we resolve the flow around each individual crystal without assuming specific settling speeds or drag coefficients. We present several benchmark problems and convergence tests to validate our approach. Key Points Developing a numerical methodology for solid‐fluid coupling Demonstrate that we can accurately reproduce the drag on immersed crystals Demonstrate that we can accurately reproduce the settling speed of crystals
Journal Article
Systemic swings in end-Permian climate from Siberian Traps carbon and sulfur outgassing
Siberian Traps flood basalt magmatism coincided with the end-Permian mass extinction approximately 252 million years ago. Proposed links between magmatism and ecological catastrophe include global warming, global cooling, ozone depletion and changes in ocean chemistry. However, the critical combinations of environmental changes responsible for global mass extinction are undetermined. In particular, the combined and competing climate effects of sulfur and carbon outgassing remain to be quantified. Here we present results from global climate model simulations of flood basalt outgassing that account for sulfur chemistry and aerosol microphysics with coupled atmosphere and ocean circulation. We consider the effects of sulfur and carbon in isolation and in tandem. We find that coupling with the ocean strongly influences the climate response to prolonged flood basalt-scale outgassing. We suggest that sulfur and carbon emissions from the Siberian Traps combined to generate systemic swings in temperature, ocean circulation and hydrology within a longer-term trend towards a greenhouse world in the early Triassic.
Journal Article
The Psyche Magnetometry Investigation
The objective of the Psyche Magnetometry Investigation is to test the hypothesis that asteroid (16) Psyche formed from the core of a differentiated planetesimal. To address this, the Psyche Magnetometer will measure the magnetic field around the asteroid to search for evidence of remanent magnetization. Paleomagnetic measurements of meteorites and dynamo theory indicate that a diversity of planetesimals once generated dynamo magnetic fields in their metallic cores. Likewise, the detection of a strong magnetic moment (
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) at Psyche would likely indicate that the body once generated a core dynamo, implying that it formed by igneous differentiation. The Psyche Magnetometer consists of two three-axis fluxgate Sensor Units (SUs) mounted 0.7 m apart along a 2.15-m long boom and connected to two Electronics Units (EUs) located within the spacecraft bus. The Magnetometer samples at up to 50 Hz, has a range of
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integrated over 0.1 to 1 Hz. The two pairs of SUs and EUs provide redundancy and enable gradiometry measurements to suppress noise from flight system magnetic fields. The Magnetometer will be powered on soon after launch and acquire data for the full duration of the mission. The ground data system processes the Magnetometer measurements to obtain an estimate of Psyche’s dipole moment.
Journal Article
The fate of water within Earth and super-Earths and implications for plate tectonics
The Earth is likely to have acquired most of its water during accretion. Internal heat of planetesimals by short-lived radioisotopes would have caused some water loss, but impacts into planetesimals were insufficiently energetic to produce further drying. Water is thought to be critical for the development of plate tectonics, because it lowers viscosities in the asthenosphere, enabling subduction. The following issue persists: if water is necessary for plate tectonics, but subduction itself hydrates the upper mantle, how is the upper mantle initially hydrated? The giant impacts of late accretion created magma lakes and oceans, which degassed during solidification to produce a heavy atmosphere. However, some water would have remained in the mantle, trapped within crystallographic defects in nominally anhydrous minerals. In this paper, we present models demonstrating that processes associated with magma ocean solidification and overturn may segregate sufficient quantities of water within the upper mantle to induce partial melting and produce a damp asthenosphere, thereby facilitating plate tectonics and, in turn, the habitability of Earth-like extrasolar planets.
This article is part of the themed issue ‘The origin, history and role of water in the evolution of the inner Solar System’.
Journal Article
Distinguishing the Origin of Asteroid (16) Psyche
The asteroid (16) Psyche may be the metal-rich remnant of a differentiated planetesimal, or it may be a highly reduced, metal-rich asteroidal material that never differentiated. The NASA Psyche mission aims to determine Psyche’s provenance. Here we describe the possible solar system regions of origin for Psyche, prior to its likely implantation into the asteroid belt, the physical and chemical processes that can enrich metal in an asteroid, and possible meteoritic analogs. The spacecraft payload is designed to be able to discriminate among possible formation theories. The project will determine Psyche’s origin and formation by measuring any strong remanent magnetic fields, which would imply it was the core of a differentiated body; the scale of metal to silicate mixing will be determined by both the neutron spectrometers and the filtered images; the degree of disruption between metal and rock may be determined by the correlation of gravity with composition; some mineralogy (e.g., modeled silicate/metal ratio, and inferred existence of low-calcium pyroxene or olivine, for example) will be detected using filtered images; and the nickel content of Psyche’s metal phase will be measured using the GRNS.
Journal Article
Formation of early water oceans on rocky planets
Terrestrial planets, with silicate mantles and metallic cores, are likely to obtain water and carbon compounds during accretion. Here I examine the conditions that allow early formation of a surface water ocean (simultaneous with cooling to clement surface conditions), and the timeline of degassing the planetary interior into the atmosphere. The greatest fraction of a planet’s initial volatile budget is degassed into the atmosphere during the end of magma ocean solidification, leaving only a small fraction of the original volatiles to be released into the atmosphere through later volcanism. Rocky planets that accrete with water in their bulk mantle have two mechanisms for producing an early water ocean: First, if they accrete with at least 1 to 3 mass% of water in their bulk composition, liquid water may be extruded onto the planetary surface at the end of magma ocean solidification. Second, at initial water contents as low as 0.01 mass% or lower, during solidification a massive supercritical fluid and steam atmosphere is produced that collapses into a water ocean upon cooling. The low water contents required for this process indicate that rocky super-Earth exoplanets may be expected to commonly produce water oceans within tens to hundreds of millions of years of their last major accretionary impact, through collapse of their atmosphere.
Journal Article
Magnetic evidence for a partially differentiated carbonaceous chondrite parent body
The textures of chondritic meteorites demonstrate that they are not the products of planetary melting processes. This has long been interpreted as evidence that chondrite parent bodies never experienced large-scale melting. As a result, the paleomagnetism of the CV carbonaceous chondrite Allende, most of which was acquired after accretion of the parent body, has been a long-standing mystery. The possibility of a core dynamo like that known for achondrite parent bodies has been discounted because chondrite parent bodies are assumed to be undifferentiated. Resolution of this conundrum requires a determination of the age and timescale over which Allende acquired its magnetization. Here, we report that Allende's magnetization was acquired over several million years (Ma) during metasomatism on the parent planetesimal in a >
Journal Article