Large-scale thermal events in the solar nebula: evidence from Fe,Ni metal grains in primitive meteorites
Chemical zoning patterns in some iron, nickel metal grains from CH carbonaceous chondrites imply formation at temperatures from 1370 to 1270 kelvin by condensation from a solar nebular gas cooling at a rate of approximately 0.2 kelvin per hour. This cooling rate requires a large-scale thermal event in the nebula, in contrast to the localized, transient heating events inferred for chondrule formation. In our model, mass accretion through the protoplanetary disk caused large-scale evaporation of precursor dust near its midplane inside of a few astronomical units. Gas convectively moved from the midplane to cooler regions above it, and the metal grains condensed in these parcels of rising gas.
Meibom
A
Hawai'i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai'i at Manoa, Honolulu, HI 96822, USA. NASA Ames Research Center, Mail Stop 245-3, Moffett Field, CA 94035, USA. Harvard-Smithson.
Desch
SJ
Krot
AN
Cuzzi
JN
Petaev
MI
Wilson
L
Keil
K