The inductive generation of a global magnetic field by the motion of conducting fluid in a planetary core is known as the dynamo. Although the moon today has no global magnetic field, recent…

The National Aeronautics and Space Administration (NASA) awarded a $519,835 grant to the Massachusetts Institute of Technology (MIT) to conduct research on the Moon's early magnetic field history. The research aims to determine if the Moon generated a convection-driven dynamo that only intermittently reached high field strengths, or if the dynamo was driven by a different process capable of producing stronger continuous fields. The key objectives are to measure the paleointensity of the lunar magnetic field and constrain the ages of these paleointensities. This work has important implications for understanding the Moon's origin, thermal history, interior structure, and orbital evolution, as well as the physics of planetary dynamo generation. The grant does not have a set-aside designation and will run through October 2025.

The inductive generation of a global magnetic field by the motion of conducting fluid in a planetary core is known as the dynamo. Although the moon today has no global magnetic field, recent paleomagnetic measurements of apollo samples indicate that the moon generated a dynamo from at least 4.25 to 1.92 billion years ago (GA). Furthermore, sample measurements suggest that prior to about 3.5 GA, a putative high-field epoch existed when the field intensity may have reached ~70 microteslas (UT) (earth-strength). However, because metallic minerals in lunar samples alter when heated in air, nearly all previous paleointensity determinations from samples older than ~3.3 GA have employed non-heating techniques, which have uncertainties ranging up to an order of magnitude or more for some samples. Dynamo scaling laws indicate that if the moon s dynamo were generated by convection in the core, its surface field should not have continuously exceeded ~10 UT over the period 4.2-3.5 GA. Therefore, if the field indeed continuously reached such values of>70 UT as tentatively suggested by existing data, then two possible explanations are (i) the lunar core generated a convective dynamo but one that only intermittently reached such high fields during this period or (II) the lunar dynamo was driven by a process other than core convection that was capable of continuously producing stronger fields. Alternatively, (III) the high apparent paleointensities are in error and the field never actually exceed 10 UT. Any of these 3 outcomes would have major implications for our understanding of the moon s origin, thermal history, interior structure, orbital history, and the physics of dynamo generation. The key to resolving this issue is to obtain accurate (0.2 billion years of history. We will conduct this work as part of two tasks: task 1. Measure the paleointensity of the lunar field using paleomagnetic analyses task 2. Constrain the ages of the paleointensities using AR-based geochronometry. If we find that the lunar field over the period ~3.4-4.9 GA was either continuously present but weaker than ~10 UT, or else greater than 10 UT but only intermittently, then this would indicate that the early dynamo could have been generated by core convection [outcome (i) above]. Alternatively, if we find that the dynamo surface field was continuously stronger than ~10 UT over this period, this would suggest that the dynamo was generated by a process other than core convection [outcome (II)]. Finally, if we find (III) that all paleointensities during this period are actually weaker than ~10 UT, then this would be compatible with a continuously operating core convection dynamo.