  It has been proposed that some meteorites, CB and CH chondrites, contain
material formed as a result of a protoplanetary collision during accretion.
Their melt droplets (chondrules) and FeNi metal are proposed to have formed by
evaporation and condensation in the resulting impact plume. We observe that the
SO (skeletal olivine) chondrules in CBb chondrites have a blebby texture and an
enrichment in refractory elements not found in normal chondrules. Since the
texture requires complete melting, their maximum liquidus temperature 1928 K
represents a minimum temperature for the putative plume. Dynamic
crystallization experiments show that the SO texture can be created only by
brief reheating episodes during crystallization giving partial dissolution of
olivine. The ejecta plume formed in a smoothed particle hydrodynamics (SPH)
simulation (Asphaug et al., 2011) served as the basis for 3D modeling with the
adaptive mesh refinement (AMR) code FLASH4.3. Tracer particles that move with
the fluid cells are used to measure the in situ cooling rates. Their cooling
rates are ~10,000K/hr briefly at peak temperature and, in the densest regions
of the plume, ~100 K/hr for 1400-1600 K. A small fraction of cells is seen to
be heating at any one time, with heating spikes explained by compression of
parcels of gas in a heterogeneous patchy plume. These temperature fluctuations
are comparable to those required in crystallization experiments. For the first
time, we find agreement between experiment and models that supports the plume
model specifically for the formation of CBb chondrules.
