A Collective Trigger for Widespread Planetesimal Formation Revealed by Accretion AgesOPEN ACCESS
James Bryson, Hannah Sanderson, Francis Nimmo, Sanjana Sridhar, Gregory Brennecka, Yves Marrocchi, Jason Terry
- We calculate formation ages of the parent planetesimals of a suite of
meteorites - NC and CC planetesimals start forming at very similar times and oc-
cupy overlapping periods - These ages indicate that both NC and CC material traversed the barrier
in our disk - NC and CC planetesimal formation was triggered by a defining fea-
ture/event - This feature/event also drove isotopic evolution throughout the proto-
planetary disk
“The formation of planetesimals was an integral part of the cascading series of processes that built the terrestrial planets. To illuminate planetesimal formation, here we develop a refined thermal evolution model to calculate the formation ages of meteorite parent planetesimals. This model includes chemical reactions and phase changes during heating, as well as natural variations in the proportions of the constituent phases of these planetesimals. We find that the parent bodies of non-carbonaceous (NC) and carbonaceous (CC) iron meteorites start forming at very similar times (~0.95 Myr after calcium-aluminium-rich inclusion [CAI] formation) and occupy overlapping time windows. NC and CC chondrite parent bodies formed later during non-overlapping periods. We combine these ages with proportions of isotopic end-members we recover from mixing models to construct records of motion throughout the protoplanetary disk. These records argue that NC and CC material traversed the barrier in the disk after ~0.95 Myr after CAI formation. The onset of this motion coincided with planetesimal formation, indicating that the phenomenon that drove motion also triggered planetesimal formation. We argue that this feature also served as the semi-permeable barrier in the disk. Although its identity is uncertain, the effects this phenomenon had on the timing of planetesimal form.”
