The Phenomenon of Shape Evolution due to Solar Driven Outgassing for Analogues of Small Kuiper Belt Objects

TL;DR

This study investigates how solar-driven outgassing influences the shape evolution of small Kuiper Belt object analogues, revealing that such activity alone cannot create concavities on convex bodies but can modify existing features.

Contribution

It provides a numerical framework to analyze the impact of solar-driven sublimation on shape changes, isolating key parameters and removing ad-hoc assumptions from previous models.

Findings

Homogeneous nuclei cannot develop concavities through outgassing.

Preexisting concavities are resistant to smoothing by sublimation.

Shape evolution depends on orbital and spin-axis parameters, including shadowing and self-heating effects.

Abstract

One of the key findings of the Rosetta's mission to the Jupiter family comet 67P/Churyumov-Gerasimenko was its peculiar bilobed shape along with the apparent north/south dichotomy in large scale morphology. This has re-ignited scientific discussions on the topic of origin, evolution and age of the nucleus. In this work we set up a general numerical investigation on the role of solar driven activity on the overall shape change. Our goal is to isolate and study the influence of key parameters for solar driven mass loss, and hopefully obtain a classification of the final shapes. We consider five general classes of three-dimensional (3D) objects for various initial conditions of spin-axis and orbital parameters, propagating them on different orbits accounting for solar driven CO ice sublimation. A detailed study of the coupling between sublimation curve and orbital parameters (for CO and H$_{2}$O ices) is also provided. The idealizations used in this study are aimed to remove the ad-hoc assumptions on activity source distribution, composition, and/or chemical inhomogeneities as applied in similar studies focusing on explaining a particular feature or observation. Our numerical experiments show that under no condition a homogeneous nucleus with solar driven outgassing can produce concave morphology on a convex shape. On the other hand, preexisting concavities can hardly be smoothed/removed for the assumed activity. In summary, the coupling between solar distance, eccentricity, spin-axis and its orientation, as well as effects on shadowing and self-heating do combine to induce morphology changes that might not be deducible without numerical simulations.