[ESAC Seminar] Angie Serafini

Title: Constraining the Early Lunar Dynamo: Paleointensity Measurements from Volcanic Glass Spherules in Apollo 17 Soil Sample 74420

Abstract:
Understanding the ancient lunar magnetic field is crucial for constraining the Moon’s geophysical evolution. The Moon’s magnetic field history suggests it once had a strong global magnetic field generated by an internal dynamo, with paleomagnetic data indicating a field strength between 40 and 110 microteslas (µT) during the period from approximately 4.25 billion years ago (Ga) to 1.92 Ga. Despite this, key uncertainties remain about the duration, intensity and mechanism driving the lunar dynamo. To investigate the strength of the magnetic field prior to 3.56 Ga, we analyzed volcanic glass spherules from Apollo 17 soil sample 74220. These rapidly cooled orange glasses are ideal magnetic recorders, having the ability to preserve a primary remnant magnetization (NRM) with minimal alteration or contamination. We measured the NRM of 50 spherules using a superconducting quantum interference device (SQUID) microscope and applied alternating field (AF) demagnetization to isolate magnetic components. Anhysteretic remnant magnetization (ARM) was also used to assess recording fidelity. Our results reveal that many spherules exhibit stable, low-coercivity components, while a subset retain high-coercivity remanence and well-behaved ARM acquisition – supporting the preservation of primary magnetization and potential for paleomagnetic field intensities above 10uT. These findings provide new constraints on the lunar dynamo and show the promise of using individual volcanic glass spherules for paleomagnetic studies of the Moon.

ESAC Student Seminar Series —

A forum for students and postdocs to share recent research, hone presentation skills, and build community among peers, sponsored by the EAPS Student Advisory Committee. Open to current EAPS graduate and undergraduate students and postdocs. Typically hosted on Thursdays during the semester, including pizza lunch.

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