The effects of transport processes on the bulk composition of the first generation of planetesimals interior to the water ice line

¹ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
² Department of Earth Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands

^★ Corresponding authors.

Received: 8 October 2024
Accepted: 11 April 2025

Abstract

Context. Knowing the carbon, hydrogen, nitrogen, oxygen, and sulfur (CHNOS) elemental budgets of rocky planets is crucial for determining their structure, evolution, and potential chemical habitability. It is unclear how the nonlocal disk processes affecting dust in planet-forming disks impact the CHNOS elemental budgets of nascent planets both inside and outside the Solar System.

Aims. We aim to quantify the coupled effect of dynamical and collisional processes on the initial refractory CHNOS budgets of planetesimals that form interior to the water ice line for a solar and non-solar composition consistent with the star HIP 43393.

Methods. We utilized the SHAMPOO code to track the effects of dynamical and collisional processes on 16 000 individual dust monomers. Each monomer was assigned a refractory chemical composition and mineralogy informed by the equilibrium condensation code GGCHEM given the Pressure-Temperature conditions at the initial position of the monomer. Monomers travel embedded in aggregates through a young class I disk, whose structure is calculated with the ProDiMo code. Furthermore, monomers are allowed to undergo dehydration and de-sulfurization.

Results. We find that solid material becomes well mixed both radially and vertically. For both the solar and HIP 43393 compositions, the solid phase in the disk midplane regions interior to r ≂ 0.7 AU can become enriched in hydrogen and sulfur by up to 10 at.% relative to predictions from purely local calculations. This originates from the inward radial transport of hydrated and sulfur-bearing minerals such as lizardite and iron sulfide.

Conclusions. Nonlocal disk processing in a young turbulent, massive disk can lead to a significant compositional homogenization of the midplane dust and, by extension, the initial composition of planetesimals. Planetesimals forming at r < 0.7 AU may become enriched in hydrated minerals and sulfur, which could result in more widespread aqueous alteration interior to the water ice line compared to planetesimals that emerge from more locally processed dust.