Local Migration of Smooth Terrain Regolith in the Imhotep Basin on Comet 67P
Abstract
Formed predominantly by air-falling debris liberated during erosion of the consolidated nucleus, the smooth terrains of comet 67P/Churyumov-Gerasimenko (67P) represent sedimentary basins of ice-rich regolith materials. The smooth terrains exhibited the most drastic changes as observed by Rosetta, and so understanding their evolution is paramount to understanding the evolution of 67P's surface. The largest smooth terrain deposit resides in the Imhotep region, which has been shown to erode via sublimation-driven scarp retreat. In this work, we provide a model that fully captures the observed loss from Imhotep's smooth terrains, and provide an estimate of the embedded ice fraction within the regolith. By combining existing shape models with photoclinometry, we have generated dozens of high-resolution (cm-scale vertical accuracy) digital terrain models (DTMs) across the Imhotep region. Using these DTMs, we have measured both the erosion and subsequent restoration of the smooth terrains. By performing these measurements on multiple OSIRIS images acquired throughout the Rosetta mission, we can map the temporal evolution of the depth of Imhotep's smooth terrains. Our work shows that the smooth terrains "drained" leading up to perihelion via the observed scarp retreat, and then "re-filled" to a greater depth after perihelion, with most material migrating locally within the Imhotep basin. These measurements provide the first direct measure of fallback on 67P, and lay the groundwork for future measurements of fallback on all other smooth terrains across the nucleus. We will discuss these measurements and their resulting implications.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P22A..06J
- Keywords:
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- 5215 Origin of life;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 6024 Interiors;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6218 Jovian satellites;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6280 Saturnian satellites;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS