Hand Magnets and the Destruction of Ancient Meteorite Magnetism

Vervelidou, Foteini; Weiss, B. P.; Lagroix, France

doi:10.1029/2022je007464

Cited by 10 publications

(8 citation statements)

References 50 publications

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“…The low NRM/IRM values (<1.5%; Tables S1, S2 in Supporting Information ) of the MBSs and bulk samples suggest that the interior of Acapulco was not substantially remagnetized by an external field since falling to Earth. Since the expected proportion of magnetic recorders aligned with an Earth‐strength external field during cooling (TRM efficiency) is ∼1% of saturation IRM (McClelland, 1996; Yu et al., 2007), the NRM/IRM of the samples are consistent with a natural form of magnetization and not artificial contamination (e.g., from a hand magnet), which would produce NRM/IRM >10% (Vervelidou et al., 2023).…”

Section: Discussionmentioning

confidence: 99%

“…This is consistent with a lack of a strong overprint which would align the magnetizations of the bulk samples and MBSs. While curved fields around hand magnets can create NRMs with smoothly varying directions as a function of depth in a sample and multiple exposures to hand magnets of different strengths from different orientations could create a scatter in the magnetization directions (Vervelidou et al., 2023), the low NRM/IRM values preclude this possibility for Acapulco. This is consistent with Acapulco being a fall given that magnet remagnetization mainly affects meteorite finds [e.g., (Weiss et al., 2008)].…”

Section: Discussionmentioning

confidence: 99%

“…We selected Acapulco for analysis because previous studies indicated it may have rock magnetic properties favorable for paleomagnetism. In particular, it is one of only two known AL falls and therefore unlikely to have been weathered on Earth [Acapulco has little to no reported weathering products (Dhaliwal et al., 2017)] or exposed to a hand magnet from a collector (Vervelidou et al., 2023; Weiss et al., 2010). Also, Acapulco retains a fusion crust, which can be used to determine whether the interior of the sample has been remagnetized through a fusion crust baked contact test (see below) (Weiss et al., 2010).…”

Section: Methodsmentioning

confidence: 99%

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Magnetism of the Acapulco Primitive Achondrite and Implications for the Evolution of Partially Differentiated Bodies

Mansbach,

Weiss,

Schnepf

et al. 2023

JGR Planets

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Primitive achondrites like the acapulcoites‐lodranites (AL) clan are meteorites that formed on bodies in the process of forming a metallic core, providing a unique window into how early solar system processes transformed unmelted material into differentiated bodies. However, the size and structure of the parent body of ALs and other primitive achondrites are largely unknown. Paleomagnetism can establish the presence or absence of a metallic core by looking for evidence of a dynamo field. We conducted a magnetic study of the Acapulco acapulcoite to determine its ferromagnetic minerals and their recording properties. This is the first detailed rock magnetic and first paleomagnetic study of a primitive achondrite group. We determined that metal inclusions inside silicate grains consist of two magnetic minerals, kamacite and tetrataenite, which have robust recording properties. However, the mechanisms and timing by which these minerals acquired any natural remanent magnetization are unknown. Despite this, Acapulco has not been substantially remagnetized since arriving on Earth and therefore should retain a record dating to 4.55 billion years ago. Future studies could characterize this record by using high‐resolution magnetometry measurements of individual populations of grains and developing an understanding of how and when they became magnetized. Our discovery of tetrataenite in ALs provides the first mineralogical evidence for slow cooling [<∼5–10 × 103°C per million years (Ma−1)] of the AL parent body at low temperatures (∼320°C). Its presence suggests the AL parent body is unlikely to have been catastrophically disrupted at AL peak temperatures (∼1,200°C) without subsequent reaccretion.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Magnetism of the Acapulco Primitive Achondrite and Implications for the Evolution of Partially Differentiated Bodies

Mansbach,

Weiss,

Schnepf

et al. 2023

JGR Planets

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“…The system was then deployed with the operator dragging the panels in a systematic search grid watching for real-time alerts for metal-rich objects. Some surface meteorites were found during these searches, where the panel system was stopped at least 5 m from the surface-spotted sample to minimize demagnetization (Vervelidou, Weiss, & Lagroix, 2023). Data logged by each coil system were reviewed each night after the panel deployment to postprocess to see if any signals in the field had been missed in real time.…”

Section: Englacial Meteorite Search Effortsmentioning

confidence: 99%

Overview of the Lost Meteorites of Antarctica field campaigns

Joy,

Smedley,

MacArthur

et al. 2024

Meteorit & Planetary Scien

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The Lost Meteorites of Antarctica project was the first UK‐led Antarctic meteorite recovery expedition. The project has successfully confirmed two new high‐density meteorite stranding zones in the Hutichison Icefield and Outer Recovery Icefields areas and investigated the geology of three previously unvisited Antarctic nunataks (Turner Nunatak, Pillinger Nunatak, Halliday Nunatak). The project undertook meteorite searching on the ice surface via skidoo reconnaissance and systematic searching and developed a novel pulse induction metal detection system to search for englacial iron‐rich meteorites trapped within the upper one meter of ice. In total, 121 meteorites have been recovered from the ice surface searching activities, which are now curated in the United Kingdom at the Natural History Museum London and are available for scientific analysis.

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“…It is noteworthy that magnetic susceptibility measurements are highly preferable to the use of hand magnets. Indeed, they offer a much better diagnostic, and most of all, they do not affect the paleomagnetic record of meteorites that is of high scientific value (e.g., Weiss et al., 2010), but is erased completely and instantaneously when using strong magnets (Gattacceca & Rochette, 2004; Savitsky, 2023; Vervelidou et al., 2023).…”

Section: Introductionmentioning

confidence: 99%

The “Meteorite meter”: A handheld instrument for the combined measurement of magnetic susceptibility and electrical conductivity, with application to meteorite identification and classification

Uehara,

Gattacceca

2023

Meteorit & Planetary Scien

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We developed a simple, handheld, and user‐friendly magnetic susceptibility meter specialized for the identification of meteorites. The measurement is based on an LC resonance circuit. When provided with a rough estimate of the sample mass, the instrument displays directly the mass‐normalized magnetic susceptibility expressed in logχm (with χm in 10−9 m3 kg−1), a parameter that is widely used in the classification of meteorites. Moreover, the measurement of the impedance of the LC resonator provides a proxy of the electrical conductivity (C‐index) that can be helpful to distinguish metal‐bearing samples from magnetite‐bearing samples. This C‐index offers an additional diagnostic for the identification of meteorites. Our tests demonstrate that the precision and the accuracy of this instrument called “Meteorite meter” (MetMet) are sufficient to allow distinguishing most meteorites from most terrestrial rocks, for a minimum recommended sample mass of 5 g. The distinction of some meteorite groups is also possible, in particular the separation of the three ordinary chondrite groups. Meteorite hunters, collectors, and curators and non‐specialists, including children, can use this instrument as a guidance in the identification and classification of meteorites. This kind of instrument has an immense advantage over the widely used testing of meteorites with magnets, as it does not affect the paleomagnetic records of meteorites that are highly valuable for scientists.

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Hand Magnets and the Destruction of Ancient Meteorite Magnetism

Cited by 10 publications

References 50 publications

Magnetism of the Acapulco Primitive Achondrite and Implications for the Evolution of Partially Differentiated Bodies

Magnetism of the Acapulco Primitive Achondrite and Implications for the Evolution of Partially Differentiated Bodies

Overview of the Lost Meteorites of Antarctica field campaigns

The “Meteorite meter”: A handheld instrument for the combined measurement of magnetic susceptibility and electrical conductivity, with application to meteorite identification and classification

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