scholarly journals The paleoinclination of the ancient lunar magnetic field from an Apollo 17 basalt

2021 ◽  
Author(s):  
Claire Nichols ◽  
Benjamin Weiss ◽  
Brenna Getzin ◽  
Harrison Schmitt ◽  
Annemarieke Beguin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Lunar Surface ◽  
Magnetic Anomalies ◽  
Wall Rock ◽  
The Moon ◽  
Polar Wander ◽  
True Polar Wander ◽  
Field Geometry ◽  
Mare Basalts ◽  
Over Time

Abstract Paleomagnetic studies of Apollo samples indicate that the Moon generated a core dynamo lasting for at least 2 billion years. However, the geometry of the lunar magnetic field is still largely unknown because the original orientations of essentially all Apollo samples have not been well-constrained. Determining the direction of the lunar magnetic field over time could elucidate the mechanism by which the lunar dynamo was powered and whether the Moon experienced true polar wander. Here we present measurements of the lunar magnetic field 3.7 billion years (Ga) ago as recorded by Apollo 17 mare basalts 75035 and 75055. These samples formed as part of basalt flows in the Taurus-Littrow valley that make up wall-rock within Camelot crater, now exposed at the rim of the crater. Using apparent layering in the parent boulder for 75055, we inferred its original paleohorizontal orientation on the lunar surface at the time of magnetization. We find that 75035 and 75055 record a mean paleointensity of ~50 µT. Furthermore, 75055 records a paleoinclination of 34 ± 11°. This inclination is consistent with, but does not require, a selenocentric axial dipole field geometry (i.e., a dipole in the center of the Moon and aligned along the spin axis). Additionally, although true polar wander is also not required by our data, true polar wander paths inferred from some independent studies of lunar hydrogen deposits and crustal magnetic anomalies are consistent with our measured paleoinclination.

The history of the core dynamos of Mars and the Moon inferred from their crustal magnetization: a brief review

2019 ◽  
Vol 56 (9) ◽  
pp. 917-931
Author(s):  
Jafar Arkani-Hamed
Keyword(s):  
The Moon ◽  
Positive Mass ◽  
Polar Wander ◽  
The Core ◽  
True Polar Wander ◽  
History Of ◽  
Giant Impacts ◽  
Crustal Magnetization ◽  
Multiple Impact ◽  
Thermochemical Convection

The core dynamos of Mars and the Moon have distinctly different histories. Mars had no core dynamo at the end of accretion. It took ∼100 Myr for the core to create a strong dynamo that magnetized the martian crust. Giant impacts during 4.2–4.0 Ga crippled the core dynamo intermittently until a thick stagnant lithosphere developed on the surface and reduced the heat flux at the core–mantle boundary, killing the dynamo at ∼3.8 Ga. On the other hand, the Moon had a strong core dynamo at the end of accretion that lasted ∼100 Myr and magnetized its primordial crust. Either precession of the core or thermochemical convection in the mantle or chemical convection in the core created a strong core dynamo that magnetized the sources of the isolated magnetic anomalies in later times. Mars and the Moon indicate dynamo reversals and true polar wander. The polar wander of the Moon is easier to explain compared to that of Mars. It was initiated by the mass deficiency at South Pole Aitken basin, which moved the basin southward by ∼68° relative to the dipole axis of the core field. The formation of mascon maria at later times introduced positive mass anomalies at the surface, forcing the Moon to make an additional ∼52° degree polar wander. Interaction of multiple impact shock waves with the dynamo, the abrupt angular momentum transfer to the mantle by the impactors, and the global overturn of the core after each impact were probably the factors causing the dynamo reversal.

scholarly journals Was the moon magnetized by impact plasmas?

2020 ◽  
Vol 6 (40) ◽  
pp. eabb1475
Author(s):  
Rona Oran ◽  
Benjamin P. Weiss ◽  
Yuri Shprits ◽  
Katarina Miljković ◽  
Gábor Tóth
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Magnetic Anomalies ◽  
The Moon ◽  
Crustal Field ◽  
Impact Simulations ◽  
Magnetizing Field

The crusts of the Moon, Mercury, and many meteorite parent bodies are magnetized. Although the magnetizing field is commonly attributed to that of an ancient core dynamo, a longstanding hypothesized alternative is amplification of the interplanetary magnetic field and induced crustal field by plasmas generated by meteoroid impacts. Here, we use magnetohydrodynamic and impact simulations and analytic relationships to demonstrate that although impact plasmas can transiently enhance the field inside the Moon, the resulting fields are at least three orders of magnitude too weak to explain lunar crustal magnetic anomalies. This leaves a core dynamo as the only plausible source of most magnetization on the Moon.

scholarly journals Magnetic Anomalies on the Pacific Plate Reveal True Polar Wander

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Aaron Sidder
Keyword(s):  
Magnetic Anomalies ◽  
Pacific Plate ◽  
Standard Approach ◽  
Polar Wander ◽  
True Polar Wander ◽  
The Pacific ◽  
New Locations ◽  
Paleomagnetic Poles

A new study rebuffs the standard approach to paleomagnetism and offers an updated methodology and new locations of paleomagnetic poles.

scholarly journals Moon’s Magnetic Field May Magnetize Iron That Hits Its Surface

Eos ◽  
2018 ◽  
Vol 99 ◽  
Author(s):  
Sarah Witman
Keyword(s):  
Magnetic Field ◽  
Satellite Data ◽  
Magnetic Anomalies ◽  
Large Impact ◽  
The Moon ◽  
Impact Basins

Scientists are using satellite data to study large impact basins on the surface of the Moon that contain magnetic anomalies.

scholarly journals An event study on broadband electric field noises and electron distributions in the lunar wake boundary

2022 ◽  
Vol 74 (1) ◽  
Author(s):  
Masaki N. Nishino ◽  
Yoshiya Kasahara ◽  
Yuki Harada ◽  
Yoshifumi Saito ◽  
Hideo Tsunakawa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electric Field ◽  
Interplanetary Magnetic Field ◽  
Electric Fields ◽  
Lunar Surface ◽  
Electron Beams ◽  
The Moon ◽  
Link Type ◽  
Electron Distributions

AbstractWave–particle interactions are fundamental processes in space plasma, and some plasma waves, including electrostatic solitary waves (ESWs), are recognised as broadband noises (BBNs) in the electric field spectral data. Spacecraft observations in recent decades have detected BBNs around the Moon, but the generation mechanism of the BBNs is not fully understood. Here, we study a wake boundary traversal with BBNs observed by Kaguya, which includes an ESW event previously reported by Hashimoto et al. Geophys Res Lett 37:L19204 10.1029/2010GL044529 (2010). Focusing on the relation between BBNs and electron pitch-angle distribution functions, we show that upward electron beams from the nightside lunar surface are effective for the generation of BBNs, in contrast to the original interpretation by Hashimoto et al. Geophys Res Lett 37:L19204 10.1029/2010GL044529 (2010) that high-energy electrons accelerated by strong ambipolar electric fields excite ESWs in the region far from the Moon. When the BBNs were observed by the Kaguya spacecraft in the wake boundary, the spacecraft’s location was magnetically connected to the nightside lunar surface, and bi-streaming electron distributions of downward-going solar wind strahl component and upward-going field-aligned beams (at $$\sim$$ ∼ 124 eV) were detected. The interplanetary magnetic field was dominated by a positive $$B_Z$$ B Z (i.e. the northward component), and strahl electrons travelled in the antiparallel direction to the interplanetary magnetic field (i.e. southward), which enabled the strahl electrons to precipitate onto the nightside lunar surface directly. The incident solar wind electrons cause negative charging of the nightside lunar surface, which generates downward electric fields that accelerate electrons from the nightside surface toward higher altitudes along the magnetic field. The bidirectional electron distribution is not a sufficient condition for the BBN generation, and the distribution of upward electron beams seems to be correlated with the BBNs. Ambipolar electric fields in the wake boundary should also contribute to the electron acceleration toward higher altitudes and further intrusion of the solar wind ions into the deeper wake. We suggest that solar wind ion intrusion into the wake boundary is also an important factor that controls the BBN generation by facilitating the influx of solar wind electrons there. Graphical Abstract

scholarly journals Late-stage magmatic outgassing from a volatile-depleted Moon

2017 ◽  
Vol 114 (36) ◽  
pp. 9547-9551 ◽  
Author(s):  
James M. D. Day ◽  
Frédéric Moynier ◽  
Charles K. Shearer
Keyword(s):  
Lunar Surface ◽  
Upper Mantle ◽  
Vapor Condensation ◽  
Internal Source ◽  
The Moon ◽  
Volatile Elements ◽  
Lunar Interior ◽  
Leaching Experiments ◽  
Mare Basalts

The abundance of volatile elements and compounds, such as zinc, potassium, chlorine, and water, provide key evidence for how Earth and the Moon formed and evolved. Currently, evidence exists for a Moon depleted in volatile elements, as well as reservoirs within the Moon with volatile abundances like Earth’s depleted upper mantle. Volatile depletion is consistent with catastrophic formation, such as a giant impact, whereas a Moon with Earth-like volatile abundances suggests preservation of these volatiles, or addition through late accretion. We show, using the “Rusty Rock” impact melt breccia, 66095, that volatile enrichment on the lunar surface occurred through vapor condensation. Isotopically light Zn (δ66Zn = −13.7‰), heavy Cl (δ37Cl = +15‰), and high U/Pb supports the origin of condensates from a volatile-poor internal source formed during thermomagmatic evolution of the Moon, with long-term depletion in incompatible Cl and Pb, and lesser depletion of more-compatible Zn. Leaching experiments on mare basalt 14053 demonstrate that isotopically light Zn condensates also occur on some mare basalts after their crystallization, confirming a volatile-depleted lunar interior source with homogeneous δ66Zn ≈ +1.4‰. Our results show that much of the lunar interior must be significantly depleted in volatile elements and compounds and that volatile-rich rocks on the lunar surface formed through vapor condensation. Volatiles detected by remote sensing on the surface of the Moon likely have a partially condensate origin from its interior.

The remanent magnetic field of the moon

1977 ◽  
Vol 285 (1327) ◽  
pp. 489-506 ◽  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Lunar Surface ◽  
Empirical Data ◽  
Energetic Particles ◽  
The Moon ◽  
Indirect Measurements ◽  
Apollo Program ◽  
Direct Measurements ◽  
Series Of Experiments

This paper is intended as a review of the empirical data on the remanent magnetic field of the Moon. These data are from direct measurements of the remanent field with magnetometers on the lunar surface and on board the Apollo subsatellites, and indirect measurements derived from studies of the interactions of the solar wind and energetic particles with the Moon. This paper is intended as a review of the empirical data on the remanent magnetic field of the Moon. These data are from direct measurements of the remanent field with magnetometers on the lunar surface and on board the Apollo subsatellites, and indirect measurements derived from studies of the interactions of the solar wind and energetic particles with the Moon. Measurements on the surface of the M oon In a series of experiments performed during the Apollo program, Sonett, Dyal, and coworkers obtained measurements of the Moon’s remanent magnetic field at the sites of Apollos 12, 14, 15 and 16. (Dyal et al. (1974) have recently reviewed this work.) Two types of vector magnetometers were used in these experiments: a fixed, or station instrument; and a portable, or traverse, unit.

scholarly journals Direct evidence of surface exposed water ice in the lunar polar regions

2018 ◽  
Vol 115 (36) ◽  
pp. 8907-8912 ◽  
Author(s):  
Shuai Li ◽  
Paul G. Lucey ◽  
Ralph E. Milliken ◽  
Paul O. Hayne ◽  
Elizabeth Fisher ◽  
...  
Keyword(s):  
Lunar Surface ◽  
Near Infrared ◽  
Direct Evidence ◽  
Polar Regions ◽  
The Moon ◽  
Optical Surface ◽  
Laser Altimeter ◽  
Polar Wander ◽  
Water Ice ◽  
Maximum Temperatures

Water ice may be allowed to accumulate in permanently shaded regions on airless bodies in the inner solar system such as Mercury, the Moon, and Ceres [Watson K, et al. (1961)J Geophys Res66:3033–3045]. Unlike Mercury and Ceres, direct evidence for water ice exposed at the lunar surface has remained elusive. We utilize indirect lighting in regions of permanent shadow to report the detection of diagnostic near-infrared absorption features of water ice in reflectance spectra acquired by the Moon Mineralogy Mapper [M (3)] instrument. Several thousand M (3) pixels (∼280 × 280 m) with signatures of water ice at the optical surface (depth of less than a few millimeters) are identified within 20° latitude of both poles, including locations where independent measurements have suggested that water ice may be present. Most ice locations detected in M (3) data also exhibit lunar orbiter laser altimeter reflectance values and Lyman Alpha Mapping Project instrument UV ratio values consistent with the presence of water ice and also exhibit annual maximum temperatures below 110 K. However, only ∼3.5% of cold traps exhibit ice exposures. Spectral modeling shows that some ice-bearing pixels may contain ∼30 wt % ice that is intimately mixed with dry regolith. The patchy distribution and low abundance of lunar surface-exposed water ice might be associated with the true polar wander and impact gardening. The observation of spectral features of H2O confirms that water ice is trapped and accumulates in permanently shadowed regions of the Moon, and in some locations, it is exposed at the modern optical surface.

New age constraints on the Ouarzazate Group (Morocco): implications on the hypothesis of True Polar Wander during the Ediacaran

2021 ◽  
Author(s):  
Boris Robert ◽  
Fernando Corfu ◽  
Olivier Blein
Keyword(s):  
Magnetic Field ◽  
Volcanic Rocks ◽  
Polar Wander ◽  
True Polar Wander ◽  
The Earth ◽  
Large Spread ◽  
Good Consistency ◽  
Global Movement ◽  
Geochronological Constraints ◽  
Age Constraints

<p>The Ediacaran (635-541 Ma) is the last geological period of the Precambrian during which major changes occurred in the superficial layers of the Earth (biosphere, cryosphere, oceans, atmosphere). The paleomagnetic data from the main continents of this epoch display very fast polar wander excursions, which seemed to occur simultaneously on several continents. Two main competing hypotheses have been proposed in the literature to explain these data: (1) very fast True Polar Wander episodes (TPW), which represent the global movement of the mantle and the crust with respect to the Earth's spin axis, or (2) perturbations of the Earth’s magnetic field. On geological timescales, the TPW is speed-limited to some degrees per million years while magnetic field changes could be much faster (degrees per kyrs). The velocity of the polar wander excursions of the Ediacaran is therefore a critical parameter to distinguish these two families of solutions. The volcanic rocks of the Ouarzazate group (575-545 Ma) in the Anti-Atlas belt recorded a large polar wander excursion from ~571 to ~565 Ma, which is also observed in Laurentia and Baltica at about the same time. Because the age uncertainties are too high, the existing SHRIMP U-Pb ages obtained on zircons are not precise enough to distinguish these two hypotheses. In this study, we bring new high-precision CA ID-TIMS ages on zircons from seven tuff layers that recorded the rapid paleomagnetic variations. Our results show, in most of the samples, a large spread in age, indicating either the presence of inherited zircons or strong Pb loss in some of the zircons. Four of the samples display a good consistency in the zircon ages, and could represent the age of the tuff emplacement. In this presentation, we will discuss the two hypotheses based on these new geochronological constraints.</p>

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