Boulder Migration in the Khonsu Region of Comet 67P/Churyumov–Gerasimenko

Abstract

The European Space Agency's Rosetta mission is the only space mission that has performed long-term monitoring of a comet at close distances. For over two years, Rosetta rendezvoused with comet 67P/Churyumov–Gerasimenko, which revealed diverse evolutionary processes of the cometary nucleus. One of the most striking events is the migration of a ∼30 m boulder in the southern hemisphere region of Khonsu. Previous works found the boulder's ∼140 m displacement occurred during the three months from 2015 August to October, and several triggering mechanisms were proposed, including outburst at the boulder site, seismic vibrations from nearby activities, or surface erosion of the slope beneath the boulder. In this work, we further analyze this impressive event by analyzing imaging data from Rosetta's OSIRIS camera. We constrained the boulder's migration time to within 14 hr and derived a detailed timeline of the boulder migration event and local dust activities. High-resolution thermophysical modeling shows significant dichotomy in the thermal history of the boulder's southern and northern sides, which could have triggered or facilitated its migration via its own volatile activity.

Keywords

• Comets
• Comet surfaces
• Coma dust
• Comet volatiles