Surface Properties, Orbital Dynamics, and Thermophysical Modeling of the Primitive Asteroid (269) Justitia

TL;DR

This study provides a comprehensive analysis of asteroid (269) Justitia's surface dynamics, equilibrium points, orbital families, and thermal properties, offering crucial insights for the upcoming EMA mission and understanding primitive asteroids.

Contribution

It introduces the first detailed dynamical and thermal modeling of Justitia, including equilibrium points, periodic orbits, and surface temperature distribution, using a new 3-D shape model.

Findings

Poles have lowest geopotential and maximum surface acceleration.

Most slopes are below 40°, indicating stable particle settlement.

Five equilibrium points identified, with two being linearly stable.

Abstract

The Emirates Mission to the Asteroid Belt (EMA) will study the ultra-red asteroid (269)~Justitia. In this work, we present the first detailed investigation of Justitia's surface dynamics using the newly developed 3-D polyhedral shape model with 574 vertices and 1,144 faces. We analyze its geopotential, surface acceleration, escape speeds, slopes, and equilibrium points, and we also search for planar symmetric periodic orbits using an equivalent ellipsoidal approximation. Our results indicate that the lowest geopotential values occur at the poles, which also correspond to regions of maximum surface acceleration. The global slope distribution suggests preferred zones of material accumulation or migration, offering clues to Justitia's long-term morphological evolution. Most slopes remain below $40^\circ$, implying that loose particles may settle stably across large portions of the surface. We identify five equilibrium points consistent with Justitia's estimated density and slow rotational period. Two external points (E$_2$ and E$_4$) exhibit linear stability, and all equilibrium locations lie relatively far from the surface due to the body's slow spin. Additionally, we discover 28 new families of planar symmetric periodic orbits, then classify their topologies and determine their linear stability, providing a dynamical framework relevant to future spacecraft operations near Justitia. Finally, thermal modeling reveals how thermal inertia and heliocentric distance shape Justitia's temperature distribution. The south pole receives more insolation than the north pole, reaching minimum temperatures of about 102~K and 87~K, respectively. These combined dynamical and thermal results offer valuable insights for the EMA mission and for understanding slowly rotating small bodies.