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Thermophysics of fractures on comet 67P/Churyumov-Gerasimenko
Max Planck Inst Sonnensyst Forsch, Goettingen; TU Braunschweig, Inst Geophys & Extraterr Phys.
Max Planck Inst Sonnensyst Forsch, Goettingen.
TU Braunschweig, Inst Geophys & Extraterr Phys.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Jet Prop Lab, Pasadena.
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2017 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 608, article id A121Article in journal (Refereed) Published
Abstract [en]

Context. The camera OSIRIS on board Rosetta obtained high-resolution images of the nucleus of comet 67P/Churyumov-Gerasimenko (67P). Great parts of the nucleus surface are composed of fractured terrain.

Aims. Fracture formation, evolution, and their potential relationship to physical processes that drive activity are not yet fully understood. Observed temperatures and gas production rates can be explained or interpreted with the presence of fractures by applying appropriate modelling methods.

Methods. We followed a transient thermophysical model approach that includes radiative, conductive, and water-ice sublimation fluxes by considering a variety of heliocentric distances, illumination conditions, and thermophysical properties for a set of characteristic fracture geometries on the nucleus of 67P. We computed diurnal temperatures, heat fluxes, and outgassing behaviour in order to derive and distinguish the influence of the mentioned parameters on fractured terrain.

Results. Our analysis confirms that fractures, as already indicated by former studies about concavities, deviate from flat-terrain topographies with equivalent properties, mostly through the effect of self-heating. Compared to flat terrain, illuminated cometary fractures are generally warmer, with smaller diurnal temperature fluctuations. Maximum sublimation rates reach higher peaks, and dust mantle quenching effects on sublimation rates are weaker. Consequently, the rough structure of the fractured terrain leads to significantly higher inferred surface thermal inertia values than for flat areas with identical physical properties, which might explain the range of measured thermal inertia on 67P.

Conclusions. At 3.5 AU heliocentric distance, sublimation heat sinks in fractures converge to maximum values >50 W / m2 and trigger dust activity that can be related mainly to H2O. Fractures are likely to grow through the erosive interplay of alternating sublimation and thermal fatigue.

Place, publisher, year, edition, pages
2017. Vol. 608, article id A121
Keywords [en]
comets: general, comets: individual: 67P/Churyumov-Gerasimenko, radiation mechanisms: thermal
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-339793DOI: 10.1051/0004-6361/201628726ISI: 000418458600015OAI: oai:DiVA.org:uu-339793DiVA, id: diva2:1185133
Funder
Swedish National Space BoardAvailable from: 2018-02-23 Created: 2018-02-23 Last updated: 2018-02-23Bibliographically approved

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Davidsson, Björn J. R.

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