Measuring Erosional and Depositional Patterns Across Comet 67P's Imhotep Region

• Published in: Journal of geophysical research. Planets 2024-02, Vol.129 (2), p.n/a
• Main Authors: Jindal, A. S., Birch, S. P. D., Hayes, A. G., Özyurt, F. P., Issah, A. B., Moruzzi, S. A., Barrington, M. N., Soderblom, J. M., Kirk, R. L., Marschall, R., Vincent, J. B.
• Format: Article
• Language: English
• Subjects: Accumulation; Cometary composition; Comets; Inner solar system; Jupiter; Measuring instruments; Northern Hemisphere; Outer solar system; Perihelions; photoclinometry; Pluto; Radiation; small bodies; Solar radiation; Southern Hemisphere; Sublimation; surface processes
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1029/2023JE008089

Comet 67P/Churyumov‐Gerasimenko displays a pronounced hemispherical dichotomy in surface morphology, where the southern hemisphere exhibits more erosional features than the northern hemisphere due to receiving much greater solar radiation. Consequently, it is generally assumed that particles are ejected from the southern hemisphere through sublimation and a significant fraction eventually descends as airfall, covering the northern terrains. To investigate this south‐to‐north material transfer during the comet's perihelion passage, we used photoclinometry to measure material redistribution within its most extensive smooth terrain deposit around the Imhotep region. However, our findings do not align with this expected trend. Instead, we show that local‐scale processes substantially impact the erosion and accumulation of material, with one area experiencing net erosion while another nearby region, just a few dozen meters away, sees sediment buildup. Our analysis underscores the complex interplay of processes shaping Comet 67P's surface and likely comets more generally. Plain Language Summary Comets are composed of some of the most primitive materials in the solar system, having spent most of their lifetimes in the far reaches of the outer solar system, shielded from the Sun's radiation. Jupiter Family Comets (JFCs) are a class of comets that get pulled into the inner solar system due to Jupiter's gravity. While JFCs still preserve abundant primordial materials, their new orbits expose them to significantly higher solar insolation, resulting in sublimation‐driven surface activity. The processes driving this activity, however, need to be better constrained. Observations of comet 67P/Churyumov‐Gerasimenko's (a JFC) surface indicate that particles are ejected from its southern hemisphere through sublimation, and a significant fraction eventually descends as “airfall,” covering its northern terrains. To investigate this south‐to‐north material transfer during the comet's perihelion passage, we measured material redistribution within its largest “airfall” deposit. However, our findings do not align with this expected trend. Instead, we show that local‐scale processes substantially impact the erosion and accumulation of material, with one area experiencing net erosion while another nearby region, just a few meters away, sees sediment buildup. Our analysis highlights the complex interplay of processes shaping Comet 67P's surface and likely comets more generally. Key