The Modular Computational Simulation Interface (MoCSI) code

I. Thermophysical model for investigating surface environments of small bodies

Institut für Planetologie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 9 September 2025
Accepted: 26 November 2025

Abstract

Context. With many different missions to small bodies and (icy) moons currently ongoing or on the horizon, modern thermophysical models for planetary science need to be able to be adapted to quickly changing parameters and science objectives.

Aims. We aim to develop the public and open-source Modular Computational Simulation Interface (MoCSI) code to offer a fully modular thermophysical model that can be applied to asteroids and to a wide variety of dry, airless bodies in the future. Further, we intend to compare MoCSI to established thermophysical models and show a proof-of-concept application to the Kolobok crater on the asteroid (162173) Ryugu.

Methods. MoCSI employs a finite element method (FEM) to solve the one-dimensional transient heat-transfer equation. Physical variables, for example thermal conductivity, bulk density, or incoming radiative flux, and different model behavior, for example dynamic time-step reduction, can be implemented through modules that the user can turn on and off to suit their science case.

Results. There is good agreement between MoCSI and the two published models 1DTM and heat1d to within < 1 K or <1%. Different treatments of the boundary conditions, especially the surface-energy-balance boundary condition, can lead to differences of >5 % during specific time-steps. The proof-of-concept application showed close agreement with the established literature.

Conclusions. MoCSI’s modular code base allows for rapid adaption, not only to different physical applications, but also to the use of different types of thermophysical models. It can be expanded to refine results and to include new physical descriptions and numerical methods. Ongoing development is planned to further improve performance and expand the available list of modules.