Quantifying Morphological Changes and Sediment Transport Pathways on Comet 67P/Churyumov-Gerasimenko

Abstract

Comets are active geological worlds with primitive surfaces that have been shaped to varying degrees by sublimation-driven sediment transport and mass wasting processes. Rosetta's rendezvous with comet 67P/Churyumov-Gerasimenko (67P) in 2014 provided data with the necessary spatial and temporal resolutions to observe many evolutionary processes on micro-gravity worlds. Rosetta's observations have thus far revealed that many changes to the surface occurred within 67P's smooth terrains, vast sedimentary deposits that blanket a significant fraction of the nucleus. Understanding the global context of these changes, and therefore the sediment transport pathways that govern the evolution of 67P's surface, requires a thorough description of their changing morphologies and an evaluation of existing global-scale spatial and temporal trends. Accordingly, we present a time-resolved synthesis of erosion and deposition activity on comet 67P as it passed through its 13 August 2015 perihelion from September 2014 to August 2016. Our mapping results indicate that, around perihelion, sediment is globally redistributed inter-regionally from 67P's more active south to the north. Equally important, however, are local, topographically influenced sediment transport processes, with large volumes of sediment moving intra-regionally over sub-kilometer distances. We also show evidence for regions of near-zero net erosion/deposition between approximately 30°N-60°N latitude, which may act as terminal sedimentary sinks, with the remobilization of these materials hindered by multiple factors. Our work therefore provides the most complete mapping of sediment transport processes and pathways across 67P, a critical step toward understanding the global landscape evolution of both 67P and other comets.