Arrival and magnetization of carbonaceous chondrites in the asteroid belt before 4562 million years ago

Timothy O’Brien,Atma Anand,Jonathan Carroll-Nellenback,Alexander N Krot,Eric G Blackman,John A Tarduno,Aleksey V Smirnov

doi:10.1038/s43247-020-00055-w

Abstract

Meteorite magnetizations can provide rare insight into early Solar System evolution. Such data take on new importance with recognition of the isotopic dichotomy between non-carbonaceous and carbonaceous meteorites, representing distinct inner and outer disk reservoirs, and the likelihood that parent body asteroids were once separated by Jupiter and subsequently mixed. The arrival time of these parent bodies into the main asteroid belt, however, has heretofore been unknown. Herein, we show that weak CV (Vigarano type) and CM (Mighei type) carbonaceous chondrite remanent magnetizations indicate acquisition by the solar wind 4.2 to 4.8 million years after Ca-Al-rich inclusion (CAI) formation at heliocentric distances of ~2–4 AU. These data thus indicate that the CV and CM parent asteroids had arrived near, or within, the orbital range of the present-day asteroid belt from the outer disk isotopic reservoir within the first 5 million years of Solar System history.

Highlights

Meteorite magnetizations can provide rare insight into early Solar System evolution
Magnetic minerals can be created and preexisting grains transformed during aqueous alteration, and such events occurred on the CM and CV parent bodies at ~4.8 and ~4.2 m.y. after Ca-Al-rich inclusion (CAI) formation, respectively[4,5]
As we will show using theory and ideal magnetohydrodynamic simulations, magnetizations can be imparted on these minerals by the solar wind, and the recorded field strength can constrain for the first time the heliocentric distance of the parent asteroids at the time of aqueous alteration

Summary

Introduction

Meteorite magnetizations can provide rare insight into early Solar System evolution. Such data take on new importance with recognition of the isotopic dichotomy between noncarbonaceous and carbonaceous meteorites, representing distinct inner and outer disk reservoirs, and the likelihood that parent body asteroids were once separated by Jupiter and subsequently mixed. Allende’s low field magnetic susceptibility (Methods, Fig. 1c, Supplementary Information Section 1) is dominated by Fe-Ni phases (predominantly awaruite, Ni3Fe) and magnetite (Fe3O4), the latter showing evidence for the Verwey transition.

Results

Conclusion