Estimating the strength of the nucleus material of comet 67P Churyumov–Gerasimenko
- Authors: Basilevsky A.T.1,2,3, Krasil’nikov S.S.1,2,3, Shiryaev A.A.4,5, Mall U.2, Keller H.U.6, Skorov Y.V.2, Mottola S.7, Hviid S.F.7
-
Affiliations:
- Vernadsky Institute of Geochemistry and Analytical Chemistry
- Max Planck Institute for Solar System Research
- Moscow State University of Geodesy and Cartography
- Institute of Physical Chemistry and Electrochemistry
- Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry
- Institute of Geophysics and Extraterrestrial Physics
- Institute of Planetary Research
- Issue: Vol 50, No 4 (2016)
- Pages: 225-234
- Section: Article
- URL: https://journal-vniispk.ru/0038-0946/article/view/170461
- DOI: https://doi.org/10.1134/S0038094616040018
- ID: 170461
Cite item
Abstract
Consideration is given to the estimates for the strength of the consolidated material forming the bulk of the nucleus of comet 67P Churyumov–Gerasimenko and those for the strength of the surface material overlying the consolidated material at the sites of the first and last contact of the Philae lander with the nucleus. The strength of the consolidated material was estimated by analyzing the terrain characteristics of the steep cliffs, where the material is exposed on the surface. Based on these estimates, the tensile strength of the material is in the range from 1.5 to 100 Pa; the shear strength, from ∼13 to ⩾30 Pa; and the compressive strength, from 30 to 150 Pa, possibly up to 1.5 kPa. These are very low strength values. Given the dependence of the measurement results on the size of the measured object, they are similar to those of fresh dry snow at –10°C. The (compressive) strength of the surface material at the site of the first touchdown of Philae on the nucleus is estimated from the measurements of the dynamics of the surface impact by the spacecraft’s legs and the geometry of the impact pits as 1–3 kPa. For comparison with the measurement results for ice-containing materials in terrestrial laboratories, it needs to be taken into account that the rate of deformation by Philae’s legs is four orders of magnitude higher than that in typical terrestrial measurements, leading to a possible overestimation of the strength by roughly an order of magnitude. There was an attemp to put one of the MUPUS sensors into the surface material at the site of the last contact of Philae with the nucleus. Noticeable penetration of the tester probe was not achieved that led to estimation of the minimum compressive strength of the material to be ⩾4 MPa4 This fairly high strength appears to indicate the presence of highly porous ice with grains “frozen” at contacts.
Keywords
About the authors
A. T. Basilevsky
Vernadsky Institute of Geochemistry and Analytical Chemistry; Max Planck Institute for Solar System Research; Moscow State University of Geodesy and Cartography
Author for correspondence.
Email: atbas@geokhi.ru
Russian Federation, Moscow; Göttingen; Moscow
S. S. Krasil’nikov
Vernadsky Institute of Geochemistry and Analytical Chemistry; Max Planck Institute for Solar System Research; Moscow State University of Geodesy and Cartography
Email: atbas@geokhi.ru
Russian Federation, Moscow; Göttingen; Moscow
A. A. Shiryaev
Institute of Physical Chemistry and Electrochemistry; Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry
Email: atbas@geokhi.ru
Russian Federation, Moscow; Moscow
U. Mall
Max Planck Institute for Solar System Research
Email: atbas@geokhi.ru
Germany, Göttingen
H. U. Keller
Institute of Geophysics and Extraterrestrial Physics
Email: atbas@geokhi.ru
Germany, Braunschweig
Yu. V. Skorov
Max Planck Institute for Solar System Research
Email: atbas@geokhi.ru
Germany, Göttingen
S. Mottola
Institute of Planetary Research
Email: atbas@geokhi.ru
Germany, Berlin
S. F. Hviid
Institute of Planetary Research
Email: atbas@geokhi.ru
Germany, Berlin
Supplementary files
