Measurements of Early Magnetic Fields in the Innermost and Outer Solar System from CO Chondrites
Abstract
Theoretical studies have long suggested that magnetic fields played a central role in the evolution of the solar nebula, mediating the transport of angular momentum and mass. Recent paleomagnetic studies of meteorites have provided the first measurements of such magnetic fields in the terrestrial planet region (1-3 AU), showing that a field ~50 μT was present at 2-3 million years (My) after the formation of calcium-aluminum-rich inclusions (CAIs). Furthermore, paleomagnetic studies of younger meteorites have determined that the solar nebula in the inner solar system (<3 AU) dissipated by <5 My. However, there have been no paleomagnetic measurements of the magnetic field in the innermost solar system (<0.1 AU) and, with the exception of ongoing studies of chondrules from CR chondrites, in the outer solar system (>5 AU).
We report on the paleomagnetism of the pristine CO3.0 chondrites DOM 08006 and ALHA 77307. CAIs from these meteorites recorded fields at <0.1 My after solar system formation likely within 0.1 AU of the Sun, while CO chondrules recorded fields at ~2.5 My after CAI formation likely beyond Jupiter, and CO bulk samples, which are dominated by matrix material, recorded fields at ~>3 AU at ~5 My after CAI formation. Our fusion crust tests demonstrate that the meteorites were not remagnetized during atmospheric entry or after landing on Earth. Additionally, we found that bulk samples from ALHA 77307 are weakly to non-magnetized (paleointensity <0.3 μT). This implies that the solar nebula beyond Jupiter likely dissipated <5 My after CAI formation, thereby marking the end of the period of gas giant formation and planetary migration. Our initial measurements of chondrules from ALHA 77307 suggest that they recorded a ~50 μT field. This is the first detection of nebular magnetic fields beyond Jupiter and strengthens the case that magnetism played an important role in accretion. This also supports nebular shocks and/or planetesimals collisions as the most likely mechanisms for forming chondrules in the outer solar system. Finally, we also present the first measurements of NRM carried by unaltered CAIs. Our ongoing experiments are attempting to measure the paleointensity of the CAI formation region.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGP31A..02B
- Keywords:
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- 1507 Core processes;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1510 Dynamo: theories and simulations;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1517 Magnetic anomalies: modeling and interpretation;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1527 Paleomagnetism applied to geologic processes;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1560 Time variations: secular and longer;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1595 Planetary magnetism: all frequencies and wavelengths;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 5440 Magnetic fields and magnetism;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS