The palaeoinclination of the ancient lunar magnetic field from an Apollo 17 basalt

Nichols, Claire; Weiss, B. P.; Getzin, B. L.; Schmitt, H. H.; Béguin, Annemarieke; Rae, Auriol S. P.; Shah, Jay

doi:10.1038/s41550-021-01469-y

Cited by 10 publications

(7 citation statements)

References 101 publications

(164 reference statements)

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“…Tetrataenite grains in cloudy zones, the adjacent rims, and in plessite range in size from tens of nm to ∼10 μm (Goldstein et al., 2009, 2014, 2017; Nichols et al., 2020, 2021). We can compare the grain sizes reported in previous studies with the SP‐SD‐two domain thresholds (Figure 2) to determine their magnetic stability.…”

Section: Discussionmentioning

confidence: 99%

Size Ranges of Magnetic Domain States in Tetrataenite

Mansbach

Shah

Williams

et al. 2022

Geochem Geophys Geosyst

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Paleomagnetic studies of meteorites provide unique constraints on the evolution of magnetic fields in the early solar system. These studies rely on the identification of magnetic minerals that can retain stable magnetizations over ≳4.5 billion years (Ga). The ferromagnetic mineral tetrataenite (γ''-Fe 0.5 Ni 0.5 ) is found in iron, stony-iron and chondrite meteorite groups. Nanoscale intergrowths of tetrataenite have been shown to carry records of paleomagnetic fields, although the effect of magnetostatic interactions on their magnetic remanence acquisition remains to be fully understood. Tetrataenite can also occur as isolated, non-interacting, nanoscale grains in many meteorite groups, although the paleomagnetic potential of these grains is particularly poorly understood. Here, we aim to improve our understanding of tetrataenite magnetization to refine our knowledge of existing paleomagnetic analyses and broaden the spectrum of meteorite groups that can be used for future paleomagnetic studies. We present the results of analytical calculations and micromagnetic modeling of isolated tetrataenite grains with various geometries. We find that tetrataenite forms a stable single domain state at grain lengths between 6 and ∼160 nm dependent on its elongation. It also possesses a magnetization resistant to viscous remagnetization over the lifetime of the solar system at 293 K. At larger grain sizes, tetrataenite's lowest energy state is a lamellar two-domain state, stable at Ga-scale timescales. Unlike many other magnetic minerals, tetrataenite does not form a single-vortex domain state due to its large uniaxial anisotropy. Our results show that single domain and two-domain tetrataenite grains carry an extremely stable magnetization and therefore are promising for paleomagnetic studies.Plain Language Summary Meteorites are fragments of small bodies created during the early solar system and therefore hold the key to understanding how planets formed and evolved. One way to further this understanding is by studying the magnetic fields recorded by these rocks. To do so requires the identification of magnetic minerals capable of retaining a record of an ancient field (in the form of a measurable magnetization) over the past 4.5 billion years. One mineral that is a potentially reliable recorder is tetrataenite (ordered Fe-Ni metal), which can be resistant to remagnetization by external fields greater than 1 T. The stability of a grain's magnetization is tied to its shape and size. Previous studies of magnetic minerals other than tetrataenite have found that the largest and smallest grains of most magnetic minerals are usually poor recorders with intermediate sizes being the most ideal. Here, we present the results of analytical calculations and numerical modeling of tetrataenite grains with various shapes and sizes to determine the conditions under which tetrataenite magnetization is stable over the lifetime of the solar system. We find that tetrataenite occupies a single-domain state (in which all magnetization is uniform t...

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Section: Discussionmentioning

confidence: 99%

Size Ranges of Magnetic Domain States in Tetrataenite

Mansbach

Shah

Williams

et al. 2022

Geochem Geophys Geosyst

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“…However, the sign of the inclination remains largely unknown, and more data are required to confirm interpretations made from lunar samples. Studies of Apollo 17 mare basalts estimated an inclination of ∼34°based on the layering of its parent boulder (Nichols et al 2021). This inclination is consistent with, but does not require, a dipole in the center of the Moon aligned along its rotation axis.…”

Section: Morphology Of the Lunar Dynamomentioning

confidence: 99%

A Long-lived Lunar Magnetic Field Powered by Convection in the Core and a Basal Magma Ocean

2023

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An internally generated magnetic field once existed on the Moon. This field reached high intensities (∼10–100 μT, perhaps intermittently) from ∼4.3 to 3.6 Gyr ago and then weakened to ≲5 μT before dissipating by ∼1.9–0.8 Gyr ago. While the Moon’s metallic core could have generated a magnetic field via a dynamo powered by vigorous convection, models of a core dynamo often fail to explain the observed characteristics of the lunar magnetic field. In particular, the core alone may not contain sufficient thermal, chemical, or radiogenic energy to sustain the high-intensity fields for >100 Myr. A recent study by Scheinberg et al. suggested that a dynamo hosted in electrically conductive, molten silicates in a basal magma ocean (BMO) may have produced a strong early field. However, that study did not fully explore the BMO’s coupled evolution with the core. Here we show that a coupled BMO–core dynamo driven primarily by inner core growth can explain the timing and staged decline of the lunar magnetic field. We compute the thermochemical evolution of the lunar core with a 1D parameterized model tied to extant simulations of mantle evolution and BMO solidification. Our models are most sensitive to four parameters: the abundances of sulfur and potassium in the core, the core’s thermal conductivity, and the present-day heat flow across the core–mantle boundary. Our models best match the Moon’s magnetic history if the bulk core contains ∼6.5–8.5 wt% sulfur, in agreement with seismic structure models.

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“…Some of the larger (≳10 cm) rock samples were oriented in lunar geographic coordinates using astronaut photographs taken with an optical camera (Kammerer & Zeiss, 1972) and a gnomon for measuring shadow angles to determine geographic north (Allton, 1989). Because the local horizontal was not marked on the samples, their orientations were reproduced after return to Earth by illuminating them under simulated lighting conditions like that during sampling (e.g., Nichols et al., 2021; Wolfe et al., 1981).…”

Section: Introductionmentioning

confidence: 99%

Oriented Bedrock Samples Drilled by the Perseverance Rover on Mars

Weiss,

Mansbach,

Carsten

et al. 2024

Earth and Space Science

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A key objective of the Perseverance rover mission is to acquire samples of Martian rocks for future return to Earth. Eventual laboratory analyses of these samples would address key questions about the evolution of the Martian climate, interior, and habitability. Many such investigations would benefit greatly from samples of Martian bedrock that are oriented in absolute Martian geographic coordinates. However, the Mars 2020 mission was designed without a requirement for orienting the samples. Here we describe a methodology that we developed for orienting rover drill cores in the Martian geographic frame and its application to Perseverance's first 20 rock samples. To orient the cores, three angles were measured: the azimuth and hade of the core pointing vector (i.e., vector oriented along the core axis) and the core roll (i.e., the solid body angle of rotation around the pointing vector). We estimated the core pointing vector from the attitude of the rover's Coring Drill during drilling. To orient the core roll, we used oriented images of asymmetric markings on the bedrock surface acquired with the rover's Wide Angle Topographic Sensor for Operations and eNgineering (WATSON) camera. For most samples, these markings were in the form of natural features on the outcrop, while for four samples they were artificial ablation pits produced by the rover's SuperCam laser. These cores are the first geographically‐oriented (<2.7° 3σ total uncertainty) bedrock samples from another planetary body. This will enable a diversity of paleomagnetic, sedimentological, igneous, tectonic, and astrobiological studies on the returned samples.

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The palaeoinclination of the ancient lunar magnetic field from an Apollo 17 basalt

Cited by 10 publications

References 101 publications

Size Ranges of Magnetic Domain States in Tetrataenite

Size Ranges of Magnetic Domain States in Tetrataenite

A Long-lived Lunar Magnetic Field Powered by Convection in the Core and a Basal Magma Ocean

Oriented Bedrock Samples Drilled by the Perseverance Rover on Mars

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