Early scattering of the solar protoplanetary disk recorded in meteoritic chondrulesOPEN ACCESS 

By Yves Marrocchi, Marc Chaussidon, Laurette Piani, Guy Libourel

Science Advances 01 Jul 2016:
Vol. 2, no. 7, e1601001
DOI: 10.1126/sciadv.1601001

Supplementary Materials (PDF)

“Meteoritic chondrules are submillimeter spherules representing the major constituent of nondifferentiated planetesimals formed in the solar protoplanetary disk. The link between the dynamics of the disk and the origin of chondrules remains enigmatic. Collisions between planetesimals formed at different heliocentric distances were frequent early in the evolution of the disk. We show that the presence, in some chondrules, of previously unrecognized magnetites of magmatic origin implies the formation of these chondrules under impact-generated oxidizing conditions. The three oxygen isotopes systematic of magmatic magnetites and silicates can only be explained by invoking an impact between silicate-rich and ice-rich planetesimals. This suggests that these peculiar chondrules are by-products of the early mixing in the disk of populations of planetesimals from the inner and outer solar system.”

Petrographic survey of magnetite-bearing Vigarano-like carbonaceous (CV) chondrules.

(A) Backscattered electron image of a porphyritic olivine-pyroxene (POP) chondrule in Kaba (CV3) revealing the preferential distribution of sulfides (FeS) and magnetites (Fe3O4) in the outer zone mainly composed of low-Ca pyroxenes. (B) Ameboidal Fe3O4 in contact with olivine, low-Ca pyroxene, and mesostasis (meso) within a chondrule of Vigarano. (C) Ameboidal Fe3O4 surrounded by mesostasis in Kaba. (D) Ameboidal Fe3O4 in contact with olivine, low-Ca pyroxene, and mesostasis within a chondrule of Vigarano. (E) Liquid-shaped Fe3O4 entrapped between olivine in a POP chondrule of Vigarano. A rounded opaque assemblage (OA) is also observed in direct contact with the magnetite. (F) Large sulfide-magnetite pool partially entrapping olivine and low-Ca pyroxenes within a chondrule of Vigarano.

Oxygen isotopic variations of SAMs and coexisting olivines within chondrules of the Kaba and Vigarano CV3 chondrites.

The orange field corresponds to the O-isotopic composition of the impact plume with which the chondrules equilibrated, as modeled (see text) to reproduce the O-isotopic composition of SAMs. There is no meteorite parent body known, either primitive (pink field) or differentiated (blue field), that corresponds to this composition. However, outer-belt icy planetesimals (enriched in 17,18O) would have oxygen isotopic composition corresponding to the impact plume. The inset shows the typical range of oxygen isotopic compositions established for the Sun, CAIs, and chondrules and ice present in meteorites. CCAM, carbonaceous chondrite anhydrous mineral.

Conditions of formation of magnetite in CV chondrules.

Oxygen fugacity as a function of temperature for a gas of solar composition (C/O = 0.5), the IW buffer, Allende inclusions, and chondrules (as determined from the iron content of olivines in type I chondrules). The fO2 required for forming and stabilizing FeSO melts (SAMs; red circles) lies ≈3 log units higher than the chondrule olivine field. This fO2 is in good agreement with that determined for impact-induced silicate melt–vapor plumes (green field).