ThermoONet: Deep learning-based small-body thermophysical network

Applications to modeling the water activity of comets

¹ School of Astronomy and Space Science, Nanjing University, Nanjing 210023, China
² Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing 210023, China
³ Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China

^★ Corresponding authors: shi@shao.ac.cn; leihl@nju.edu.cn

Received: 22 March 2025
Accepted: 29 April 2025

Abstract

Cometary activity is a compelling subject of study, with thermophysical models playing a pivotal role in its understanding. However, traditional numerical solutions for small body thermophysical models are computationally intensive, posing challenges for investigations requiring high-resolution or repetitive modeling. To address this limitation, we employed a machine learning approach to develop ThermoONet – a neural network designed to predict the temperature and water ice sublimation flux of comets. Performance évaluations indicate that ThermoONet achieves a low average error in subsurface temperature of approximately 2% relative to the numerical simulation, while reducing the computational time by nearly six orders of magnitude. We applied ThermoONet to model the water activity of comets 67P/Churyumov-Gerasimenko and 21P/Giacobini-Zinner. By successfully fitting the water production rate curves of these comets, obtained by the Rosetta mission and the SOHO telescope, respectively, we have been able to demonstrate the network's effectiveness and efficiency. Furthermore, when combined with a global optimization algorithm, ThermoONet proves capable of retrieving the physical properties of target bodies.