Characterizing the Modulation and Activation‐Triggering Mechanisms of Main‐Belt Comets via 3D Thermophysical Modeling of an Ellipsoidal Body

Main-belt objects (MBOs) with volatile components provide important insights into the solar system's evolution and the origin of Earth's water. In this study, we employ a 3D thermophysical model to simulate the evolution of a representative ellipsoidal main-belt comet (MBC) and investigate the factors influencing its gas and dust activity. Our results highlight the important role of large obliquities in amplifying the detectability of sublimation-driven dust emission in MBCs. For the modeled ellipsoidal 133P/Elst-Pizarro, we found an obliquity of at least <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>∼</mml:mo> <mml:mn>30</mml:mn> <mml:mo>°</mml:mo></mml:mrow> </mml:mrow> </mml:math> is likely required to sustain a dust production rate of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>∼</mml:mo></mml:mrow> </mml:mrow> </mml:math> 0.01 kg/s (this required obliquity increases to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>≥</mml:mo> <mml:mo>∼</mml:mo> <mml:mn>45</mml:mn> <mml:mo>°</mml:mo></mml:mrow> </mml:mrow> </mml:math> for a dust production rate of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>≥</mml:mo> <mml:mo>∼</mml:mo></mml:mrow> </mml:mrow> </mml:math> 0.1 kg/s). By exploring the influence of locations and sizes of ice-exposed surface regions, we find that both the impact-triggered and landslide-triggered ice-exposure mechanisms can lead to detectable dust and gas activities for the modeled MBC. With probable distributions of ice-exposed surface regions, our results show that MBCs' sublimation-driven activity should be predominantly detectable near perihelion, independent of the true anomaly at solstice and the activation-triggering mechanism. Moreover, we find that the landslide-triggered mechanism results in dual peaks in dust and gas emission curves. This enables potential differentiation between the two mechanisms, suggesting that monitoring of MBCs' activity at various orbital positions is important to discern the underlying activation-triggering mechanism. Our analyses provide quantitative constraints on producing the observable cometary activity in ice-containing MBOs and highlight the importance of studying the rotational evolution and structural dynamics of ice-containing MBOs in characterizing their overall population.