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Chondrule formation by repeated evaporative melting and condensation in collisional debris clouds around planetesimals
Author(s) -
RUZICKA Alex
Publication year - 2012
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/j.1945-5100.2012.01412.x
Subject(s) - chondrule , planetesimal , chondrite , formation and evolution of the solar system , astrobiology , geology , settling , snow , nebula , debris , meteorite , geochemistry , solar system , physics , astrophysics , stars , geomorphology , oceanography , thermodynamics
– A synthesis of previous work leads to a model of chondrule formation that involves periodic melting of dispersed dust in debris clouds that were generated by collisions between chondritic planetesimals. I suggest that chondrules formed by the passage of nebular shock waves through these dust clumps, which temporarily surrounded disrupted planetesimals. Type I chondrules formed by more intense evaporative heating of fewer particles in tenuous clumps, or at the edges of dense clumps, and type II chondrules formed by less intense evaporative heating of more particles deeper within dense clumps. Chondrules reaccreted by self‐gravity into the planetesimals, mixing with less heated dust and rock. This process of disruption, melting, and reaccretion could have repeated many times. In this way, chondrite components of various origins and thermal histories could remain preserved in planetesimals as a distinctive mix of materials for extended periods of time, while still allowing for a repetitive melting process that converted some of the planetesimal debris into chondrules. I also suggest that during chondrule formation, the inner solar nebula gas was evolving by the gradual incorporation and heating of icy bodies depleted in 16 O, causing a general increase in gaseous Δ 17 O with time in most places, especially close to the “snow line.” In this model, early formed type I chondrules in C chondrites with lower Δ 17 O values were produced inside the snow line, and later formed type I and type II chondrules in C and O chondrites with higher Δ 17 O values were created nearer the snow line after it had moved closer to the young Sun.