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 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.

The early magnetic field and primeval satellite system of the Moon: clues to planetary formation

1994 ◽  
Vol 349 (1690) ◽  
pp. 181-196 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Anomalies ◽  
Satellite System ◽  
Iron Core ◽  
Planetary Formation ◽  
The Moon ◽  
The Core ◽  
Basin Formation ◽  
The Mean ◽  
The Moment

From the stable remanent magnetization of the Apollo igneous rocks and high-grade breccias the existence of a primeval lunar magnetic field was inferred. The palaeointensities of the samples rise rapidly to a maximum at 3.9 Ga, then decrease exponentially to 3.2 Ga, strongly suggesting that the Moon had a field generated in a core, the existence of which was inferred from its non-hydrostatic figure. Modelling of the Apollo 15 and 16 subsatellite magnetic anomalies, by P. J. Coleman, L. L. Hood and C. T. Russell, gave palaeomagnetic directions of crustal strata. This enabled N pole positions to be calculated, which were empirically found to form three bipolar groups, the mean poles of which define (on the core dynamo hypothesis) three axes of rotation different from the present. These were dated as Pre-Nectarian, Lower Nectarian, and Upper Nectarian-Imbrian. Multi-ring basins of these ages were found to lie close to the corresponding palaeo-equators. The impacting bodies were therefore satellites, not asteroids or comets. Their velocities, before collision, can be shown (from basin asymmetries) to be nearly equatorial. The consequent changes in the moment of inertia tensor by basin formation caused these successive reorientations of the Moon relative to its axis of rotation in space. The three mean poles form a 90° spherical triangle. The explanation is that the Moon had three satellites: the orbits of each decayed, they broke up at the Roche limit into smaller bodies, which produced impact basins near the equator. The Moon then reorientated according to Euler’s principle before the next group of impacts. Lunar palaeomagnetism, and especially the inferences that the Moon has an iron core that segregated late and had a primeval satellite system, may provide important constraints on theories of lunar and planetary formation.

Simulations of Magnetic Fields Produced by Asteroid Impact: Possible Implications for Planetary Paleomagnetism

2019 ◽  
Author(s):  
David A. Crawford
Keyword(s):  
Magnetic Field ◽  
Magnetic Measurements ◽  
Magnetic Anomalies ◽  
Iron Core ◽  
The Moon ◽  
Major Question ◽  
Asteroid Impact ◽  
Origin And Evolution ◽  
The Impact ◽  
The Magnetic Field

Abstract The origin and evolution of the Moon's magnetic field has been a major question in lunar science ever since Luna 1 made the first magnetic measurements in the vicinity of the Moon in 1959. Orbital measurements show that the magnetic field at the surface of the Moon has local scale lengths on the order of 1-100 km. While this could suggest a correlation with impact craters, most lunar magnetic anomalies don’t appear to correlate with known geologic structures, including impacts [1]. However, the magnetic field produced by impact events are spatially and temporally complex. Add in the complexity of remanence acquisition (localized regions of heating/cooling and/or shock that can produce remanence in the presence of a magnetic field) and we have the potential for a complex pattern to emerge. Wieczorek et al. [1] showed just how such complexity may play out. In their simulations, some lunar magnetic anomalies may be caused by regions of concentrated magnetic materials associated with fragments of the South Pole-Aitken impactor, especially if the impactor was differentiated with an iron core. More recently, Oliveira et al. [2] showed that magnetic anomalies associated with five large lunar basins may be caused by impact melt sheets that cooled in the presence of an early lunar dynamo. In this paper we will look at an alternative explanation for many lunar anomalies that doesn’t require the presence of a lunar dynamo. At least some lunar anomalies may be associated with a deeper, thicker yet more varied region of magnetization acquired by rocks that became hot and cooled rapidly enough during crater formation to have acquired the transient magnetic field produced by the impact itself.

Lunar surface magnetic field concentrations antipodal to young large impact basins

Icarus ◽  
1988 ◽  
Vol 74 (3) ◽  
pp. 529-541 ◽  
Author(s):  
R.P. Lin ◽  
K.A. Anderson ◽  
L.L. Hood
Keyword(s):  
Magnetic Field ◽  
Lunar Surface ◽  
Large Impact ◽  
Surface Magnetic Field ◽  
Impact Basins

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.

Large scale magnetic anomalies over western Canada and the Arctic: a discussion

1976 ◽  
Vol 13 (6) ◽  
pp. 790-802 ◽  
Author(s):  
R. L. Coles ◽  
G. V. Haines ◽  
W. Hannaford
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Elevated Temperatures ◽  
Magnetic Anomalies ◽  
The Arctic ◽  
Evolutionary Development ◽  
Magnetic Feature ◽  
Western Canada ◽  
Arctic Regions ◽  
The Magnetic Field

A contoured map of vertical magnetic field residuals (relative to the IGRF) over western Canada and adjacent Arctic regions has been produced by amalgamating new data with those from previous surveys. The measurements were made at altitudes between 3.5 and 5.5 km above sea level. The map shows the form of the magnetic field within the waveband 30 to 5000 km. A magnetic feature of several thousand kilometres wavelength dominates the map, and is probably due in major part to sources in the earth's core. Superimposed on this are several groups of anomalies which contain wavelengths of the order of a thousand kilometres. The patterns of the short wavelength anomalies provide a broad view of major structures and indicate several regimes of distinctive evolutionary development. Enhancement of viscous magnetization at elevated temperatures may account for the concentration of intense anomalies observed near the western edge of the craton.

Stochastic Late Accretion to Earth, the Moon, and Mars

Science ◽  
2010 ◽  
Vol 330 (6010) ◽  
pp. 1527-1530 ◽  
Author(s):  
William F. Bottke ◽  
Richard J. Walker ◽  
James M. D. Day ◽  
David Nesvorny ◽  
Linda Elkins-Tanton
Keyword(s):  
Size Distribution ◽  
Asteroid Belt ◽  
The Moon ◽  
Core Formation ◽  
Highly Siderophile Elements ◽  
Earth’S Mantle ◽  
Distribution Matching ◽  
Siderophile Elements ◽  
Impact Basins

Core formation should have stripped the terrestrial, lunar, and martian mantles of highly siderophile elements (HSEs). Instead, each world has disparate, yet elevated HSE abundances. Late accretion may offer a solution, provided that ≥0.5% Earth masses of broadly chondritic planetesimals reach Earth’s mantle and that ~10 and ~1200 times less mass goes to Mars and the Moon, respectively. We show that leftover planetesimal populations dominated by massive projectiles can explain these additions, with our inferred size distribution matching those derived from the inner asteroid belt, ancient martian impact basins, and planetary accretion models. The largest late terrestrial impactors, at 2500 to 3000 kilometers in diameter, potentially modified Earth’s obliquity by ~10°, whereas those for the Moon, at ~250 to 300 kilometers, may have delivered water to its mantle.

Sign in / Sign up

Export Citation Format

Share Document