Work

Sublimation-driven fragmentation of icy dust aggregates in main-belt comets

Year: 2026

Type: article

Abstract: Context . The post-release fragmentation behavior of dust from main-belt comets (MBCs) significantly alters the particle size distribution and number density, thereby affecting the accuracy of dust impact risk assessments for spacecraft. Aims . We aim to construct a coupled thermophysical and mechanical model for porous MBCs’ dust to evaluate their structural stability and investigate the physical mechanisms of sublimation-driven disintegration. Methods . We constructed a refined thermophysical model for porous MBCs’ dust by integrating the ballistic particle-cluster aggregation algorithm with a hybrid radiative-transfer strategy and solving the coupled energy–mass balance equations using the finite element method. By comparing the sublimation-induced internal pore pressure with the effective tensile strength of the hierarchical aggregate structure, a critical failure criterion was established to evaluate the mechanism of dust fragmentation. Results . Numerical simulations reveal strict size selectivity for sublimation-driven fragmentation. At a heliocentric distance of 1.69 AU, sublimation-driven fragmentation is confined to a narrow size range approximately bounded by 50 and 70 mm if the secondary aggregate size is 1/5 of the macroscopic aggregate size. Furthermore, increasing heliocentric distance generally suppresses sublimation-induced internal pressure buildup, while both the bulk porosity and secondary aggregate size significantly influence gas transport, tensile-strength thresholds, and the resulting fragmentation outcome. Conclusions . Sublimation-driven fragmentation is identified as the hierarchical disintegration of millimeter- and centimeter-sized aggregates at low stress thresholds. Since the predicted critical sizes significantly exceed sizes of typical tail dust grains, we conclude that this mechanism is a near-surface phenomenon occurring prior to dust entrainment, rather than a process occurring within the comet tail.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202659698