Dynamical Constraints on the Origin of (269) Justitia

Asteroid (269) Justitia, the primary target of the Emirates Mission to the Asteroid Belt, may preserve evidence of large-scale radial mixing in the early Solar System. We investigate its origin using a combination of orbital dynamics and surface-color constraints.

We perform N-body integrations over 100 Myr using WHFast in REBOUND, sampling orbital elements within Justitia’s observational uncertainties and varying the semimajor axis to explore the dynamical landscape in its neighborhood. Our results indicate that Justitia’s orbit is only marginally stable, with a 34% probability of scattering or ejection over this timescale. Figure 1 also shows that Justitia’s local dynamical environment is highly structured, with stability peaks and valleys produced by overlapping three-body mean-motion resonances and secular resonances with Jupiter and Saturn. In particular, we show that Justitia lies in both the g − 2g₆ + g₅​ nonlinear secular resonance and the 2J + 2S − 1 three-body mean-motion resonance. These dynamical results place stringent constraints on models of Justitia’s formation and emplacement.

We then place Justitia’s unusually red surface color in the context of trans-Neptunian object populations, identifying compositional affinities with outer Solar System bodies, particularly Centaurs. We also show how such objects could evolve onto Justitia-like orbits.

Finally, motivated by these dynamical and spectral results, we propose a new emplacement pathway for Justitia and support it with additional N-body simulations.