Title: Impact splash chondrule formation during planetesimal recycling,
Abstract: Chondrules are the dominant bulk silicate constituent of chondritic
meteorites and originate from highly energetic, local processes during the
first million years after the birth of the Sun. So far, an astrophysically
consistent chondrule formation scenario, explaining major chemical, isotopic
and textural features, remains elusive. Here, we examine the prospect of
forming chondrules from planetesimal collisions. We show that intensely melted
bodies with interior magma oceans became rapidly chemically equilibrated and
physically differentiated. Therefore, collisional interactions among such
bodies would have resulted in chondrule-like but basaltic spherules, which are
not observed in the meteoritic record. This inconsistency with the expected
dynamical interactions hints at an incomplete understanding of the planetary
growth regime during the protoplanetary disk phase. To resolve this conundrum,
we examine how the observed chemical and isotopic features of chondrules
constrain the dynamical environment of accreting chondrite parent bodies by
interpreting the meteoritic record as an impact-generated proxy of
planetesimals that underwent repeated collision and reaccretion cycles. Using a
coupled evolution-collision model we demonstrate that the vast majority of
collisional debris feeding the asteroid main belt must be derived from
planetesimals which were partially molten at maximum. Therefore, the precursors
of chondrite parent bodies either formed primarily small, from sub-canonical
aluminum-26 reservoirs, or collisional destruction mechanisms were efficient
enough to shatter planetesimals before they reached the magma ocean phase.
Finally, we outline the window in parameter space for which chondrule formation
from planetesimal collisions can be reconciled with the meteoritic record and
how our results can be used to further constrain early solar system dynamics.