Tracing the main belt origins of S-complex near-Earth objects: From space mission targets to meteorite sources

The study addresses how space missions to near-Earth objects (NEOs) can characterise their physical and compositional properties, but interpreting those results requires knowing their provenance—the source family in the main asteroid belt. The authors aim to identify the family sources of six S-complex NEOs that have been or will soon be visited by spacecraft, and to investigate the size-dependent orbital behaviour of the broader S-complex NEO population using the MITHNEOS dataset.

They combine near-infrared spectral fitting with ordinary chondrite (OC) analogues reddened by a space-weathering model, using reduced χ² minimisation. They cross-validate these spectral classifications with probabilistic dynamical maps of the main NEO source families.

The analysis links Eros, Itokawa, Apophis, and Torifune to LL6–7 chondrites and the Flora family; Toutatis to LL3 chondrites and the Nysa family; and Didymos–Dimorphos to L chondrites and the Massalia family. For Itokawa and Eros, where in situ observations exist, the classifications are consistent. Applied to the broader S-complex NEO population, the spectral classification and orbital property distributions are broadly consistent with dynamical models.

After accounting for observational biases, the authors find that at small diameters (≤100 m), the fractions of H- and L-type objects increase at the expense of LL6–7 types, with low-inclination orbits consistent with origins in the Massalia (L) and Koronis (H) families. They conclude that combining spectral fitting with OC analogues and dynamical probability maps robustly identifies source families of individual NEOs. Below D ~100 m, the compositional distribution of S-complex NEOs approaches that of meteorite falls, providing direct observational evidence—from spectroscopic measurements of S-complex NEOs—of the emergence of the source regions of OC meteorites.