Constraints on planetesimal accretion inferred from particle-size distribution in CO chondrites

Abstract

The formation of planetesimals was a key step in the assemblage of planetary bodies, yet many aspects of their formation remain poorly constrained. Notably, the mechanism by which chondrules -- sub-millimetric spheroids that dominate primitive meteorites -- were incorporated into planetesimals remains poorly understood. Here we classify and analyze particle-size distributions in various CO carbonaceous chondrites found in the Atacama Desert. Our results show that the average circle-equivalent diameters of chondrules define a positive trend with the petrographic grade, which reflects the progressive role of thermal metamorphism within the CO parent body. We show that this relationship could not have been established by thermal metamorphism alone but rather by aerodynamic sorting during accretion. By modeling the self-gravitational contraction of clumps of chondrules, we show that (i) the accretion of the CO parent body(ies) would have generated a gradual change of chondrule size with depth in the parent body, with larger chondrules being more centrally concentrated than smaller ones, and (ii) any subsequent growth by pebble accretion would have been insignificant. These findings give substantial support to the view that planetesimals formed via gravitational collapse.

arXiv commentAccepted in ApJL. 24 pages, 3 figures, 2 tables, 1 appendix

References in corpus (19)

• Streaming Instabilities in Protoplanetary Disks
• Rapid growth of gas-giant cores by pebble accretion
• The effect of gas drag on the growth of protoplanets -- Analytical expressions for the accretion of small bodies in laminar disks
• Particle Clumping and Planetesimal Formation Depend Strongly on Metallicity
• Towards planetesimals: dense chondrule clumps in the protoplanetary nebula
• Size-selective concentration of chondrules and other small particles in protoplanetary nebula turbulence
• Concentrating small particles in protoplanetary disks through the streaming instability
• How to form planetesimals from mm-sized chondrules and chondrule aggregates
• Close-in planetesimal formation by pile-up of drifting pebbles
• Turbulence sets the length scale for planetesimal formation: Local 2D simulations of streaming instability and planetesimal formation
• Abundance, Major Element Composition and Size of Components and Matrix in CV, CO and Acfer 094 Chondrites
• Demographics of Planetesimals Formed by the Streaming Instability
• On the Numerical Robustness of the Streaming Instability: Particle Concentration and Gas Dynamics in Protoplanetary Disks
• Requirements for gravitational collapse in planetesimal formation --- the impact of scales set by Kelvin-Helmholtz and nonlinear streaming instability
• Testing the Jeans, Toomre and Bonnor-Ebert concepts for planetesimal formation: 3D streaming instability simulations of diffusion regulated formation of planetesimals
• Timing of thermal metamorphism in CM chondrites: implication for Ryugu and Bennu future sample return
• Shocks and Star Formation in Stephan's Quintet. I. Gemini Spectroscopy of Hα-bright knots
• Collisions and compositional variability in chondrule-forming events
• Radially resolved simulations of collapsing pebble clouds in protoplanetary discs

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