Boulder migration in the Khonsu region of comet 67P/Churyumov-Gerasimenko

TL;DR

This study analyzes a rare boulder migration event on comet 67P/Churyumov-Gerasimenko, using Rosetta's imaging data to constrain its timing and explore potential triggers like thermal activity and surface erosion.

Contribution

It provides a detailed timeline and thermophysical analysis of the boulder's migration, offering new insights into comet surface dynamics and volatile activity triggers.

Findings

Migration constrained within 14 hours

Thermal dichotomy may have triggered movement

Detailed timeline of the event derived

Abstract

European Space Agency's Rosetta mission is the only space mission that performed long-term monitoring of comet at close distances. Its over two years' rendezvous with comet 67P/Churyumov-Gerasimenko 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 August to October 2015, 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 analysing imaging data from Rosetta's OSIRIS camera. We constrained the boulder's migration time to within 14 hours and derived a detailed timeline of the boulder migration event and local dust activities. High-resolution thermophysical modelling 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.