EAGER: Determining When Earth's Magnetic Field Originated

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It is currently unknown when the Earth?s magnetic field originated. This timing has major implications for the thermal evolution of the interior, the physics of dynamo action, and the evolution of the terrestrial atmosphere. Paleomagnetic studies of the oldest known unmetamorphosed rocks indicate that a field with intensity similar to that of the present existed at least 3.5 billion years (Ga) ago. Here we describe a project that could potentially determine its time of origin and earliest evolution. Detrital zircon crystals found in sandstones from the Jack Hills of Western Australia are the oldest known earthly materials. Ranging from 3.0-4.38 Ga in age, they may preserve a record of the origin of Earth?s geodynamo. Some of these zircons carry an extremely weak remanent magnetization. Depending on their thermal and alteration histories, the Jack Hills zircons may therefore provide the earliest known paleointensity records of the Earth?s field. The PIs will conduct research that will help determine the time when the Earth's magnetic field began. This is important for understanding how the planet has evolved over time. The PIs plan to share theirr results in public lectures at local science museums and as part of podcasts and local science festivals. They also plan to share results at multidisciplinary conferences. The PIs will train MIT undergraduates in research techniques. Finally, this project will further stimulate the development of next generation paleomagnetism techniques for the analysis of extremely weakly magnetic materials.