Neptune Trojans and Plutinos: colors, sizes, dynamics, and their possible collisions

TL;DR

This study investigates the collisional interactions, size distributions, and color characteristics of Neptune Trojans and Plutinos, suggesting collisions may influence their observed properties and population dynamics over geological timescales.

Contribution

It provides a detailed analysis of the potential collisional interactions between Neptune Trojans and Plutinos, linking orbital dynamics with observed color and size distributions.

Findings

Orbital overlap is more likely for Plutinos with large libration amplitudes, high eccentricities, and small inclinations.

Collisions may produce smaller, differently colored objects, explaining the abundance of small, faint Plutinos.

High collision rates could significantly modify the size distribution of these trans-Neptunian populations.

Abstract

Neptune Trojans and Plutinos are two subpopulations of trans-Neptunian objects located in the 1:1 and the 3:2 mean motion resonances with Neptune, respectively, and therefore protected from close encounters with the planet. However, the orbits of these two kinds of objects may cross very often, allowing a higher collisional rate between them than with other kinds of trans-Neptunian objects, and a consequent size distribution modification of the two subpopulations. Observational colors and absolute magnitudes of Neptune Trojans and Plutinos show that i) there are no intrinsically bright (large) Plutinos at small inclinations, ii) there is an apparent excess of blue and intrinsically faint (small) Plutinos, and iii) Neptune Trojans possess the same blue colors as Plutinos within the same (estimated) size range do. For the present subpopulations we analyzed the most favorable conditions for close encounters/collisions and address any link there could be between those encounters and the sizes and/or colors of Plutinos and Neptune Trojans. We also performed a simultaneous numerical simulation of the outer Solar System over 1 Gyr for all these bodies in order to estimate their collisional rate. We conclude that orbital overlap between Neptune Trojans and Plutinos is favored for Plutinos with large libration amplitudes, high eccentricities, and small inclinations. Additionally, with the assumption that the collisions can be disruptive creating smaller objects not necessarily with similar colors, the present high concentration of small Plutinos with small inclinations can thus be a consequence of a collisional interaction with Neptune Trojans and such hypothesis should be further analyzed.