Cauê Borlina: Measurements of Solar Nebula Magnetic Fields from CO chondrites
Channel: Institute for Rock Magnetism
Date: 2021-06-01

12th Institute for Rock Magnetism Conference

Lightning Talk

Title: Measurements of Solar Nebula Magnetic Fields from CO chondrites

Authors: Cauê S. Borlina (1), Benjamin P. Weiss (1), James F. J. Bryson (2), Xue-Ning Bai (3), Eduardo A. Lima (1), Nilanjan Chatterjee (1) & Elias N. Mansbach(1)

Institutions:
(1) Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
(2) Department of Earth Sciences, University of Oxford, Oxford, UK
(3) Institute for Advanced Study, Tsinghua University, Beijing, China

Abstract
Astronomical observations have shown that the presence of disk substructures, such as cavities, rings and gaps, are common in protoplanetary disks and they can play a central role in planetary formation and regulating the lifetime of the disk. A gap has been proposed to exist in our protoplanetary disk based on isotopic measurements of meteorites that show that they derive from two main reservoirs: the non-carbonaceous (NC) and carbonaceous (CC) reservoirs. Because the evolution of protoplanetary disks is thought to depend on the coupling of the weakly ionized gas of the disk with large-scale magnetic fields, we can search for the presence of disk substructures in the early solar system by studying the paleomagnetism of meteorites that formed in these reservoirs. Previous paleomagnetic studies identified a robust record of the magnetic field in the NC reservoir and a lower limit on the magnetic field in the CC reservoir during the first 3 million years (Ma) after the formation of calcium-aluminum-rich inclusions (CAIs). Here we report robust records of the magnetic field from the CC reservoir ~2.2 Ma after CAI formation.

We measured the remanence carried by chondrules from the CO carbonaceous chondrites DOM 08006 (type 3.00) and ALHA 77307 (type 3.03). CO chondrules recorded fields at ~2.2 Ma after CAI formation in the CC reservoir. We targeted dusty olivine chondrules, which are known to be robust paleomagnetic recorders containing fine metal grains in the single vortex state that formed prior to accretion of the CO parent body. The samples were demagnetized using stepwise alternating fields (AF) and their natural remanent magnetization measured using superconducting quantum interference device (SQUID) microscopy and quantum diamond microscopy (QDM). Paleointensity estimates for the chondrules were acquired using anhysteretic remanent magnetization methods calibrated for dusty olivine thermoremanent magnetization.

Our results support the presence of nebular magnetic fields in the CC reservoir at ~2.2 Ma after CAI formation with a mean paleointensity of 101 ± 48 μT (2σ). When compared to previous measurements and models that predict the expected spatial variation in the magnetic field in protoplanetary disk, our measurements support the presence of a significant variation in the accretion rates between the two reservoirs, indicating a much higher accretion rate in the CC reservoir. This mismatch in the accretion rates implies significant mass loss from the disk associated with a major disk substructure, possibly due to a magnetized disk wind. This disk substructure is likely to be related to the observed isotopic dichotomy. Additionally, we will report on initial paleomagnetic measurements of CAIs, which could extend the record of the solar nebula magnetic field back to the first less than 0.1 Ma of solar system history.