Thermal fracturing on comets. Applications to 67P/Churyumov-Gerasimenko

Attree, N.; Groussin, O.; Jorda, L.; Rodionov, S.; Auger, A-T.; Thomas, Nicolas; Brouet, Yann; Poch, Olivier; Kührt, E.; Knapmeyer, M.; Preusker, F.; Scholten, F.; Knollenberg, J.; Hviid, S.; Hartogh, P. (2018). Thermal fracturing on comets. Applications to 67P/Churyumov-Gerasimenko. Astronomy and astrophysics, 610(A76), A76. EDP Sciences 10.1051/0004-6361/201731937

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We simulate the stresses induced by temperature changes in a putative hard layer near the surface of comet 67P/Churyumov–Gerasimenko with a thermo-viscoelastic model. Such a layer could be formed by the recondensation or sintering of water ice (and dust grains), as suggested by laboratory experiments and computer simulations, and would explain the high compressive strength encountered by experiments on board the Philae lander. Changes in temperature from seasonal insolation variation penetrate into the comet’s surface to depths controlled by the thermal inertia, causing the material to expand and contract. Modelling this with a Maxwellian viscoelastic response on a spherical nucleus, we show that a hard, icy layer with similar properties to Martian permafrost will experience high stresses: up to tens of MPa, which exceed its material strength (a few MPa), down to depths of centimetres to a metre. The stress distribution with latitude is confirmed qualitatively when taking into account the comet’s complex shape but neglecting thermal inertia. Stress is found to be comparable to the material strength everywhere for sufficient thermal inertia Stress is found to be comparable to the material strength everywhere for sufficient thermal inertia (≥ 50 J m⁻² K⁻¹ s⁻¹/²) and ice content (≥ 45% at the equator). In this case, stresses penetrate to a typical depth of ~ 0.25 m, consistent with the detection of metre-scale thermal contraction crack polygons all over the comet. Thermal fracturing may be an important erosion process on cometary surfaces which breaks down material and weakens cliffs.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Thomas, Nicolas; Brouet, Yann and Poch, Olivier

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering

ISSN:

0004-6361

Publisher:

EDP Sciences

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

28 Mar 2018 10:19

Last Modified:

22 Mar 2019 10:56

Publisher DOI:

10.1051/0004-6361/201731937

BORIS DOI:

10.7892/boris.112216

URI:

https://boris.unibe.ch/id/eprint/112216

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