comets

ACTIVE PROJECTS

Quantifying Sediment Transport Pathways and Rates on Comet 67P

Co-authors: Dr Samuel Birch.

Institution: Brown University Department of Earth, Environmental, and Planetary Sciences.

Comets are amongst the most primitive bodies in the solar system, the remnants of the solar nebula in which they formed, and therefore embody the materials from which the planets were fashioned from. These relics thus act as a lens by which to explore the evolution of the early solar system and can enlighten us as to the initial conditions under which the planets formed, the composition and formation of pre-solar materials, and processes acting in the protoplanetary disk. Comets, however, are not merely frozen in time, their surface expressions and comae are fluid and that which we observe today has been physically and chemically altered to varying and unknown degrees by active geological processes such that their modern morphologies do not mirror their primitive state. The Rosetta mission to comet 67P/Churyumov–Gerasimenko has provided unprecedented resolution of a cometary surface in time and space, allowing us to deduce that smooth terrains – spatially vast basins of non-consolidated material into which sediment is deposited via airfall – contain the vast majority of morphological changes documented on 67P over the duration of the mission. Despite these immense advancements in our understanding of cometary geomorphology, we do not yet fully grasp the context under which these observed changes of 67P’s surface occurred. Up to this point, hypotheses as to the evolution of 67P have been put forward, but as of yet, they remain untested as the required database of all changes observed on 67P only recently became available. Fortunately, we are now at the point in time where we can employ quantitative models to test specific hypotheses about how exactly 67P’s surface evolved, how mass transport on small bodies occurs, and how these primitive icy surfaces evolve physically and chemically. To do so, we will conduct an array of numerical dust transport simulations that will be grounded by the database of changes observed on 67P. Specifically, we will couple two well-tested models: a thermal evolution model previously employed on 67P, and a dust transport model used extensively to understand 67P’s coma and fallback dynamics. We will use this coupled framework to test specific hypotheses that remain unanswered following the creation of the database of observed changes. The key outcome of our work will be quantitative estimates of the rates and volumes of sediment deposition and erosion across 67P’s smooth terrains. The hypotheses we hope to address over the course of this investigation include (but are not limited to): (1) if the lack of activity observed in the Ash is the result of if little sediment was delivered to Ash or sediment inputs were balanced by sediment losses before/after perihelion, (2) that the delivery of sediment into Hapi is limited throughout perihelion by the significant topography surrounding Hapi, and (3) the filling of Ma’at was due to material being eroded from nearby Hapi.