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    Evidence for geologic processes on comets

    Sunshine, J.M. and Thomas, N. and El-Maarry, Mohamed Ramy and Farnham, T.L. (2016) Evidence for geologic processes on comets. Journal of Geophysical Research: Planets 121 (11), pp. 2194-2210. ISSN 2169-9097.

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    Spacecraft missions have resolved the nuclei of six periodic comets and revealed a set of geologically intriguing and active small bodies. The shapes of these cometary nuclei are dominantly bilobate reflecting their formation from smaller cometesimals. Cometary surfaces include a diverse set of morphologies formed from a variety of mechanisms. Sublimation of ices, driven by the variable insolation over the time since each nucleus was perturbed into the inner Solar System, is a major process on comets and is likely responsible for quasi‐circular depressions and ubiquitous layering. Sublimation from near‐vertical walls is also seen to lead to undercutting and mass wasting. Fracturing has only been resolved on one comet but likely exists on all comets. There is also evidence for mass redistribution, where material lifted off the nucleus by subliming gases is deposited onto other surfaces. It is surprising that such sedimentary processes are significant in the microgravity environment of comets. There are many enigmatic features on cometary surfaces including tall spires, kilometer‐scale flows, and various forms of depressions and pits. Furthermore, even after accounting for the differences in resolution and coverage, significant diversity in landforms among cometary surfaces clearly exists. Yet why certain landforms occur on some comets and not on others remains poorly understood. The exploration and understanding of geologic processes on comets is only beginning. These fascinating bodies will continue to provide a unique laboratory for examining common geologic processes under the uncommon conditions of very high porosity, very low strength, small particle sizes, and near‐zero gravity.


    Item Type: Article
    Keyword(s) / Subject(s): comets, morphology, surfaces, Planetary sciences: Comets and small bodies surfaces, erosion and weathering, origin and evolution
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Natural Sciences
    Depositing User: Administrator
    Date Deposited: 17 Oct 2018 18:33
    Last Modified: 02 Aug 2023 17:45


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