title: Large-scale thermal events in the solar nebula: evidence from Fe,Ni metal grains in primitive meteorites
abstract: 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.
authors.affiliation: 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.
authors.initials: A
authors.lastname: Meibom
authors.initials: SJ
authors.lastname: Desch
authors.initials: AN
authors.lastname: Krot
authors.initials: JN
authors.lastname: Cuzzi
authors.initials: MI
authors.lastname: Petaev
authors.initials: L
authors.lastname: Wilson
authors.initials: K
authors.lastname: Keil