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May 20, 2023

Hand Magnets Destroy the Magnetic Record of Meteorites

Meteorites provide crucial evidence of the processes at play during the early

Meteorites provide crucial evidence of the processes at play during the early solar system. They help us understand how planets form and evolve. Records of ancient magnetic fields help constrain how the core of a planet, such as Mars, cooled over time and the role of other geological processes in the crust. Until samples collected by rovers are returned from the red planet, meteorites are the only rocks that can help address these topics, if they include a reliable record of their magnetic history. However, this record can be destroyed if care is not taken to protect samples from acquiring magnetic contamination during sample collection and handling. Unfortunately, touching meteorites with a strong magnet, which is a common strategy to classify them, can destroy their magnetic record.

Vervelidou et al. [2023] highlight the devastating effects of magnetic contamination on NWA 7034, a precious meteorite that otherwise would have been one of the most promising Martian samples. Unlike other Martian meteorites, it may have formed when the planet supported an active core dynamo. However, the magnetic record of NWA 7034 was destroyed when a strong magnet was used to classify the meteorite.

This study aims to raise awareness of the issue of magnetic contamination to the entire planetary and meteoritics community. It encourages scientists and collectors to take care during sample collection and recommends using magnetic susceptibility meters instead of handheld magnets to differentiate meteorites from terrestrial rocks. Magnetic susceptibility meters do not destroy the sample's natural remanence. Preventing magnetic contamination is also relevant to the upcoming Artemis missions and other sample return missions that NASA and other global space agencies are pursuing in the coming decade.

Citation: Vervelidou, F., Weiss, B. P., & Lagroix, F. (2023). Hand magnets and the destruction of ancient meteorite magnetism. Journal of Geophysical Research: Planets, 128, e2022JE007464. https://doi.org/10.1029/2022JE007464

—Laurent G. J. Montesi, Editor in Chief, JGR: Planets, and Sonia Tikoo, Associate Editor, JGR: Planets